2 See the "run control" section for a working example of the
3 syntax to use when making .mdp entries, with and without detailed
4 documentation for values those entries might take. Everything can
5 be cross-referenced, see the examples there.
7 .. todo:: Make more cross-references.
9 Molecular dynamics parameters (.mdp options)
10 ============================================
17 Default values are given in parentheses, or listed first among
18 choices. The first option in the list is always the default
19 option. Units are given in square brackets. The difference between a
20 dash and an underscore is ignored.
22 A :ref:`sample mdp file <mdp>` is available. This should be
23 appropriate to start a normal simulation. Edit it to suit your
24 specific needs and desires.
32 directories to include in your topology. Format:
33 ``-I/home/john/mylib -I../otherlib``
37 defines to pass to the preprocessor, default is no defines. You can
38 use any defines to control options in your customized topology
39 files. Options that act on existing :ref:`top` file mechanisms
42 ``-DFLEXIBLE`` will use flexible water instead of rigid water
43 into your topology, this can be useful for normal mode analysis.
45 ``-DPOSRES`` will trigger the inclusion of ``posre.itp`` into
46 your topology, used for implementing position restraints.
54 (Despite the name, this list includes algorithms that are not
55 actually integrators over time. :mdp-value:`integrator=steep` and
56 all entries following it are in this category)
60 A leap-frog algorithm for integrating Newton's equations of motion.
64 A velocity Verlet algorithm for integrating Newton's equations
65 of motion. For constant NVE simulations started from
66 corresponding points in the same trajectory, the trajectories
67 are analytically, but not binary, identical to the
68 :mdp-value:`integrator=md` leap-frog integrator. The kinetic
69 energy, which is determined from the whole step velocities and
70 is therefore slightly too high. The advantage of this integrator
71 is more accurate, reversible Nose-Hoover and Parrinello-Rahman
72 coupling integration based on Trotter expansion, as well as
73 (slightly too small) full step velocity output. This all comes
74 at the cost off extra computation, especially with constraints
75 and extra communication in parallel. Note that for nearly all
76 production simulations the :mdp-value:`integrator=md` integrator
79 .. mdp-value:: md-vv-avek
81 A velocity Verlet algorithm identical to
82 :mdp-value:`integrator=md-vv`, except that the kinetic energy is
83 determined as the average of the two half step kinetic energies
84 as in the :mdp-value:`integrator=md` integrator, and this thus
85 more accurate. With Nose-Hoover and/or Parrinello-Rahman
86 coupling this comes with a slight increase in computational
91 An accurate and efficient leap-frog stochastic dynamics
92 integrator. With constraints, coordinates needs to be
93 constrained twice per integration step. Depending on the
94 computational cost of the force calculation, this can take a
95 significant part of the simulation time. The temperature for one
96 or more groups of atoms (:mdp:`tc-grps`) is set with
97 :mdp:`ref-t`, the inverse friction constant for each group is
98 set with :mdp:`tau-t`. The parameters :mdp:`tcoupl` and :mdp:`nsttcouple`
99 are ignored. The random generator is initialized with
100 :mdp:`ld-seed`. When used as a thermostat, an appropriate value
101 for :mdp:`tau-t` is 2 ps, since this results in a friction that
102 is lower than the internal friction of water, while it is high
103 enough to remove excess heat NOTE: temperature deviations decay
104 twice as fast as with a Berendsen thermostat with the same
109 An Euler integrator for Brownian or position Langevin dynamics,
110 the velocity is the force divided by a friction coefficient
111 (:mdp:`bd-fric`) plus random thermal noise (:mdp:`ref-t`). When
112 :mdp:`bd-fric` is 0, the friction coefficient for each particle
113 is calculated as mass/ :mdp:`tau-t`, as for the integrator
114 :mdp-value:`integrator=sd`. The random generator is initialized
119 A steepest descent algorithm for energy minimization. The
120 maximum step size is :mdp:`emstep`, the tolerance is
125 A conjugate gradient algorithm for energy minimization, the
126 tolerance is :mdp:`emtol`. CG is more efficient when a steepest
127 descent step is done every once in a while, this is determined
128 by :mdp:`nstcgsteep`. For a minimization prior to a normal mode
129 analysis, which requires a very high accuracy, |Gromacs| should be
130 compiled in double precision.
132 .. mdp-value:: l-bfgs
134 A quasi-Newtonian algorithm for energy minimization according to
135 the low-memory Broyden-Fletcher-Goldfarb-Shanno approach. In
136 practice this seems to converge faster than Conjugate Gradients,
137 but due to the correction steps necessary it is not (yet)
142 Normal mode analysis is performed on the structure in the :ref:`tpr`
143 file. |Gromacs| should be compiled in double precision.
147 Test particle insertion. The last molecule in the topology is
148 the test particle. A trajectory must be provided to ``mdrun
149 -rerun``. This trajectory should not contain the molecule to be
150 inserted. Insertions are performed :mdp:`nsteps` times in each
151 frame at random locations and with random orientiations of the
152 molecule. When :mdp:`nstlist` is larger than one,
153 :mdp:`nstlist` insertions are performed in a sphere with radius
154 :mdp:`rtpi` around a the same random location using the same
155 pair list. Since pair list construction is expensive,
156 one can perform several extra insertions with the same list
157 almost for free. The random seed is set with
158 :mdp:`ld-seed`. The temperature for the Boltzmann weighting is
159 set with :mdp:`ref-t`, this should match the temperature of the
160 simulation of the original trajectory. Dispersion correction is
161 implemented correctly for TPI. All relevant quantities are
162 written to the file specified with ``mdrun -tpi``. The
163 distribution of insertion energies is written to the file
164 specified with ``mdrun -tpid``. No trajectory or energy file is
165 written. Parallel TPI gives identical results to single-node
166 TPI. For charged molecules, using PME with a fine grid is most
167 accurate and also efficient, since the potential in the system
168 only needs to be calculated once per frame.
172 Test particle insertion into a predefined cavity location. The
173 procedure is the same as for :mdp-value:`integrator=tpi`, except
174 that one coordinate extra is read from the trajectory, which is
175 used as the insertion location. The molecule to be inserted
176 should be centered at 0,0,0. |Gromacs| does not do this for you,
177 since for different situations a different way of centering
178 might be optimal. Also :mdp:`rtpi` sets the radius for the
179 sphere around this location. Neighbor searching is done only
180 once per frame, :mdp:`nstlist` is not used. Parallel
181 :mdp-value:`integrator=tpic` gives identical results to
182 single-rank :mdp-value:`integrator=tpic`.
186 Enable MiMiC QM/MM coupling to run hybrid molecular dynamics.
187 Keey in mind that its required to launch CPMD compiled with MiMiC as well.
188 In this mode all options regarding integration (T-coupling, P-coupling,
189 timestep and number of steps) are ignored as CPMD will do the integration
190 instead. Options related to forces computation (cutoffs, PME parameters,
191 etc.) are working as usual. Atom selection to define QM atoms is read
192 from :mdp:`QMMM-grps`
197 starting time for your run (only makes sense for time-based
203 time step for integration (only makes sense for time-based
209 maximum number of steps to integrate or minimize, -1 is no
215 The starting step. The time at step i in a run is
216 calculated as: t = :mdp:`tinit` + :mdp:`dt` *
217 (:mdp:`init-step` + i). The free-energy lambda is calculated
218 as: lambda = :mdp:`init-lambda` + :mdp:`delta-lambda` *
219 (:mdp:`init-step` + i). Also non-equilibrium MD parameters can
220 depend on the step number. Thus for exact restarts or redoing
221 part of a run it might be necessary to set :mdp:`init-step` to
222 the step number of the restart frame. :ref:`gmx convert-tpr`
223 does this automatically.
225 .. mdp:: simulation-part
228 A simulation can consist of multiple parts, each of which has
229 a part number. This option specifies what that number will
230 be, which helps keep track of parts that are logically the
231 same simulation. This option is generally useful to set only
232 when coping with a crashed simulation where files were lost.
236 .. mdp-value:: Linear
238 Remove center of mass translational velocity
240 .. mdp-value:: Angular
242 Remove center of mass translational and rotational velocity
244 .. mdp-value:: Linear-acceleration-correction
246 Remove center of mass translational velocity. Correct the center of
247 mass position assuming linear acceleration over :mdp:`nstcomm` steps.
248 This is useful for cases where an acceleration is expected on the
249 center of mass which is nearly constant over :mdp:`nstcomm` steps.
250 This can occur for example when pulling on a group using an absolute
255 No restriction on the center of mass motion
260 frequency for center of mass motion removal
264 group(s) for center of mass motion removal, default is the whole
273 (0) [amu ps\ :sup:`-1`]
274 Brownian dynamics friction coefficient. When :mdp:`bd-fric` is 0,
275 the friction coefficient for each particle is calculated as mass/
281 used to initialize random generator for thermal noise for
282 stochastic and Brownian dynamics. When :mdp:`ld-seed` is set to -1,
283 a pseudo random seed is used. When running BD or SD on multiple
284 processors, each processor uses a seed equal to :mdp:`ld-seed` plus
285 the processor number.
293 (10.0) [kJ mol\ :sup:`-1` nm\ :sup:`-1`]
294 the minimization is converged when the maximum force is smaller
305 frequency of performing 1 steepest descent step while doing
306 conjugate gradient energy minimization.
311 Number of correction steps to use for L-BFGS minimization. A higher
312 number is (at least theoretically) more accurate, but slower.
315 Shell Molecular Dynamics
316 ^^^^^^^^^^^^^^^^^^^^^^^^
318 When shells or flexible constraints are present in the system the
319 positions of the shells and the lengths of the flexible constraints
320 are optimized at every time step until either the RMS force on the
321 shells and constraints is less than :mdp:`emtol`, or a maximum number
322 of iterations :mdp:`niter` has been reached. Minimization is converged
323 when the maximum force is smaller than :mdp:`emtol`. For shell MD this
324 value should be 1.0 at most.
329 maximum number of iterations for optimizing the shell positions and
330 the flexible constraints.
335 the step size for optimizing the flexible constraints. Should be
336 chosen as mu/(d2V/dq2) where mu is the reduced mass of two
337 particles in a flexible constraint and d2V/dq2 is the second
338 derivative of the potential in the constraint direction. Hopefully
339 this number does not differ too much between the flexible
340 constraints, as the number of iterations and thus the runtime is
341 very sensitive to fcstep. Try several values!
344 Test particle insertion
345 ^^^^^^^^^^^^^^^^^^^^^^^
350 the test particle insertion radius, see integrators
351 :mdp-value:`integrator=tpi` and :mdp-value:`integrator=tpic`
360 number of steps that elapse between writing coordinates to the output
361 trajectory file (:ref:`trr`), the last coordinates are always written
366 number of steps that elapse between writing velocities to the output
367 trajectory file (:ref:`trr`), the last velocities are always written
372 number of steps that elapse between writing forces to the output
373 trajectory file (:ref:`trr`), the last forces are always written.
378 number of steps that elapse between writing energies to the log
379 file, the last energies are always written
381 .. mdp:: nstcalcenergy
384 number of steps that elapse between calculating the energies, 0 is
385 never. This option is only relevant with dynamics. This option affects the
386 performance in parallel simulations, because calculating energies
387 requires global communication between all processes which can
388 become a bottleneck at high parallelization.
393 number of steps that elapse between writing energies to energy file,
394 the last energies are always written, should be a multiple of
395 :mdp:`nstcalcenergy`. Note that the exact sums and fluctuations
396 over all MD steps modulo :mdp:`nstcalcenergy` are stored in the
397 energy file, so :ref:`gmx energy` can report exact energy averages
398 and fluctuations also when :mdp:`nstenergy` > 1
400 .. mdp:: nstxout-compressed
403 number of steps that elapse between writing position coordinates
404 using lossy compression (:ref:`xtc` file)
406 .. mdp:: compressed-x-precision
409 precision with which to write to the compressed trajectory file
411 .. mdp:: compressed-x-grps
413 group(s) to write to the compressed trajectory file, by default the
414 whole system is written (if :mdp:`nstxout-compressed` > 0)
418 group(s) for which to write to write short-ranged non-bonded
419 potential energies to the energy file (not supported on GPUs)
425 .. mdp:: cutoff-scheme
427 .. mdp-value:: Verlet
429 Generate a pair list with buffering. The buffer size is
430 automatically set based on :mdp:`verlet-buffer-tolerance`,
431 unless this is set to -1, in which case :mdp:`rlist` will be
436 Generate a pair list for groups of atoms, corresponding
437 to the charge groups in the topology. This option is no longer
446 Frequency to update the neighbor list. When dynamics and
447 :mdp:`verlet-buffer-tolerance` set, :mdp:`nstlist` is actually
448 a minimum value and :ref:`gmx mdrun` might increase it, unless
449 it is set to 1. With parallel simulations and/or non-bonded
450 force calculation on the GPU, a value of 20 or 40 often gives
451 the best performance.
455 The neighbor list is only constructed once and never
456 updated. This is mainly useful for vacuum simulations in which
457 all particles see each other. But vacuum simulations are
458 (temporarily) not supported.
468 Use periodic boundary conditions in all directions.
472 Use no periodic boundary conditions, ignore the box. To simulate
473 without cut-offs, set all cut-offs and :mdp:`nstlist` to 0. For
474 best performance without cut-offs on a single MPI rank, set
475 :mdp:`nstlist` to zero and :mdp-value:`ns-type=simple`.
479 Use periodic boundary conditions in x and y directions
480 only. This works only with :mdp-value:`ns-type=grid` and can be used
481 in combination with walls_. Without walls or with only one wall
482 the system size is infinite in the z direction. Therefore
483 pressure coupling or Ewald summation methods can not be
484 used. These disadvantages do not apply when two walls are used.
486 .. mdp:: periodic-molecules
490 molecules are finite, fast molecular PBC can be used
494 for systems with molecules that couple to themselves through the
495 periodic boundary conditions, this requires a slower PBC
496 algorithm and molecules are not made whole in the output
498 .. mdp:: verlet-buffer-tolerance
500 (0.005) [kJ mol\ :sup:`-1` ps\ :sup:`-1`]
502 Used when performing a simulation with dynamics. This sets
503 the maximum allowed error for pair interactions per particle caused
504 by the Verlet buffer, which indirectly sets :mdp:`rlist`. As both
505 :mdp:`nstlist` and the Verlet buffer size are fixed (for
506 performance reasons), particle pairs not in the pair list can
507 occasionally get within the cut-off distance during
508 :mdp:`nstlist` -1 steps. This causes very small jumps in the
509 energy. In a constant-temperature ensemble, these very small energy
510 jumps can be estimated for a given cut-off and :mdp:`rlist`. The
511 estimate assumes a homogeneous particle distribution, hence the
512 errors might be slightly underestimated for multi-phase
513 systems. (See the `reference manual`_ for details). For longer
514 pair-list life-time (:mdp:`nstlist` -1) * :mdp:`dt` the buffer is
515 overestimated, because the interactions between particles are
516 ignored. Combined with cancellation of errors, the actual drift of
517 the total energy is usually one to two orders of magnitude
518 smaller. Note that the generated buffer size takes into account
519 that the |Gromacs| pair-list setup leads to a reduction in the
520 drift by a factor 10, compared to a simple particle-pair based
521 list. Without dynamics (energy minimization etc.), the buffer is 5%
522 of the cut-off. For NVE simulations the initial temperature is
523 used, unless this is zero, in which case a buffer of 10% is
524 used. For NVE simulations the tolerance usually needs to be lowered
525 to achieve proper energy conservation on the nanosecond time
526 scale. To override the automated buffer setting, use
527 :mdp:`verlet-buffer-tolerance` =-1 and set :mdp:`rlist` manually.
532 Cut-off distance for the short-range neighbor list. With dynamics,
533 this is by default set by the :mdp:`verlet-buffer-tolerance` option
534 and the value of :mdp:`rlist` is ignored. Without dynamics, this
535 is by default set to the maximum cut-off plus 5% buffer, except
536 for test particle insertion, where the buffer is managed exactly
537 and automatically. For NVE simulations, where the automated
538 setting is not possible, the advised procedure is to run :ref:`gmx grompp`
539 with an NVT setup with the expected temperature and copy the resulting
540 value of :mdp:`rlist` to the NVE setup.
548 .. mdp-value:: Cut-off
550 Plain cut-off with pair list radius :mdp:`rlist` and
551 Coulomb cut-off :mdp:`rcoulomb`, where :mdp:`rlist` >=
556 Classical Ewald sum electrostatics. The real-space cut-off
557 :mdp:`rcoulomb` should be equal to :mdp:`rlist`. Use *e.g.*
558 :mdp:`rlist` =0.9, :mdp:`rcoulomb` =0.9. The highest magnitude
559 of wave vectors used in reciprocal space is controlled by
560 :mdp:`fourierspacing`. The relative accuracy of
561 direct/reciprocal space is controlled by :mdp:`ewald-rtol`.
563 NOTE: Ewald scales as O(N\ :sup:`3/2`) and is thus extremely slow for
564 large systems. It is included mainly for reference - in most
565 cases PME will perform much better.
569 Fast smooth Particle-Mesh Ewald (SPME) electrostatics. Direct
570 space is similar to the Ewald sum, while the reciprocal part is
571 performed with FFTs. Grid dimensions are controlled with
572 :mdp:`fourierspacing` and the interpolation order with
573 :mdp:`pme-order`. With a grid spacing of 0.1 nm and cubic
574 interpolation the electrostatic forces have an accuracy of
575 2-3*10\ :sup:`-4`. Since the error from the vdw-cutoff is larger than
576 this you might try 0.15 nm. When running in parallel the
577 interpolation parallelizes better than the FFT, so try
578 decreasing grid dimensions while increasing interpolation.
580 .. mdp-value:: P3M-AD
582 Particle-Particle Particle-Mesh algorithm with analytical
583 derivative for for long range electrostatic interactions. The
584 method and code is identical to SPME, except that the influence
585 function is optimized for the grid. This gives a slight increase
588 .. mdp-value:: Reaction-Field
590 Reaction field electrostatics with Coulomb cut-off
591 :mdp:`rcoulomb`, where :mdp:`rlist` >= :mdp:`rvdw`. The
592 dielectric constant beyond the cut-off is
593 :mdp:`epsilon-rf`. The dielectric constant can be set to
594 infinity by setting :mdp:`epsilon-rf` =0.
598 Currently unsupported.
599 :ref:`gmx mdrun` will now expect to find a file ``table.xvg``
600 with user-defined potential functions for repulsion, dispersion
601 and Coulomb. When pair interactions are present, :ref:`gmx
602 mdrun` also expects to find a file ``tablep.xvg`` for the pair
603 interactions. When the same interactions should be used for
604 non-bonded and pair interactions the user can specify the same
605 file name for both table files. These files should contain 7
606 columns: the ``x`` value, ``f(x)``, ``-f'(x)``, ``g(x)``,
607 ``-g'(x)``, ``h(x)``, ``-h'(x)``, where ``f(x)`` is the Coulomb
608 function, ``g(x)`` the dispersion function and ``h(x)`` the
609 repulsion function. When :mdp:`vdwtype` is not set to User the
610 values for ``g``, ``-g'``, ``h`` and ``-h'`` are ignored. For
611 the non-bonded interactions ``x`` values should run from 0 to
612 the largest cut-off distance + :mdp:`table-extension` and
613 should be uniformly spaced. For the pair interactions the table
614 length in the file will be used. The optimal spacing, which is
615 used for non-user tables, is ``0.002 nm`` when you run in mixed
616 precision or ``0.0005 nm`` when you run in double precision. The
617 function value at ``x=0`` is not important. More information is
618 in the printed manual.
620 .. mdp-value:: PME-Switch
622 Currently unsupported.
623 A combination of PME and a switch function for the direct-space
624 part (see above). :mdp:`rcoulomb` is allowed to be smaller than
627 .. mdp-value:: PME-User
629 Currently unsupported.
630 A combination of PME and user tables (see
631 above). :mdp:`rcoulomb` is allowed to be smaller than
632 :mdp:`rlist`. The PME mesh contribution is subtracted from the
633 user table by :ref:`gmx mdrun`. Because of this subtraction the
634 user tables should contain about 10 decimal places.
636 .. mdp-value:: PME-User-Switch
638 Currently unsupported.
639 A combination of PME-User and a switching function (see
640 above). The switching function is applied to final
641 particle-particle interaction, *i.e.* both to the user supplied
642 function and the PME Mesh correction part.
644 .. mdp:: coulomb-modifier
646 .. mdp-value:: Potential-shift
648 Shift the Coulomb potential by a constant such that it is zero
649 at the cut-off. This makes the potential the integral of the
650 force. Note that this does not affect the forces or the
655 Use an unmodified Coulomb potential. This can be useful
656 when comparing energies with those computed with other software.
658 .. mdp:: rcoulomb-switch
661 where to start switching the Coulomb potential, only relevant
662 when force or potential switching is used
667 The distance for the Coulomb cut-off. Note that with PME this value
668 can be increased by the PME tuning in :ref:`gmx mdrun` along with
669 the PME grid spacing.
674 The relative dielectric constant. A value of 0 means infinity.
679 The relative dielectric constant of the reaction field. This
680 is only used with reaction-field electrostatics. A value of 0
689 .. mdp-value:: Cut-off
691 Plain cut-off with pair list radius :mdp:`rlist` and VdW
692 cut-off :mdp:`rvdw`, where :mdp:`rlist` >= :mdp:`rvdw`.
696 Fast smooth Particle-mesh Ewald (SPME) for VdW interactions. The
697 grid dimensions are controlled with :mdp:`fourierspacing` in
698 the same way as for electrostatics, and the interpolation order
699 is controlled with :mdp:`pme-order`. The relative accuracy of
700 direct/reciprocal space is controlled by :mdp:`ewald-rtol-lj`,
701 and the specific combination rules that are to be used by the
702 reciprocal routine are set using :mdp:`lj-pme-comb-rule`.
706 This functionality is deprecated and replaced by using
707 :mdp-value:`vdwtype=Cut-off` with :mdp-value:`vdw-modifier=Force-switch`.
708 The LJ (not Buckingham) potential is decreased over the whole range and
709 the forces decay smoothly to zero between :mdp:`rvdw-switch` and
712 .. mdp-value:: Switch
714 This functionality is deprecated and replaced by using
715 :mdp-value:`vdwtype=Cut-off` with :mdp-value:`vdw-modifier=Potential-switch`.
716 The LJ (not Buckingham) potential is normal out to :mdp:`rvdw-switch`, after
717 which it is switched off to reach zero at :mdp:`rvdw`. Both the
718 potential and force functions are continuously smooth, but be
719 aware that all switch functions will give rise to a bulge
720 (increase) in the force (since we are switching the
725 Currently unsupported.
726 See user for :mdp:`coulombtype`. The function value at zero is
727 not important. When you want to use LJ correction, make sure
728 that :mdp:`rvdw` corresponds to the cut-off in the user-defined
729 function. When :mdp:`coulombtype` is not set to User the values
730 for the ``f`` and ``-f'`` columns are ignored.
732 .. mdp:: vdw-modifier
734 .. mdp-value:: Potential-shift
736 Shift the Van der Waals potential by a constant such that it is
737 zero at the cut-off. This makes the potential the integral of
738 the force. Note that this does not affect the forces or the
743 Use an unmodified Van der Waals potential. This can be useful
744 when comparing energies with those computed with other software.
746 .. mdp-value:: Force-switch
748 Smoothly switches the forces to zero between :mdp:`rvdw-switch`
749 and :mdp:`rvdw`. This shifts the potential shift over the whole
750 range and switches it to zero at the cut-off. Note that this is
751 more expensive to calculate than a plain cut-off and it is not
752 required for energy conservation, since Potential-shift
753 conserves energy just as well.
755 .. mdp-value:: Potential-switch
757 Smoothly switches the potential to zero between
758 :mdp:`rvdw-switch` and :mdp:`rvdw`. Note that this introduces
759 articifically large forces in the switching region and is much
760 more expensive to calculate. This option should only be used if
761 the force field you are using requires this.
766 where to start switching the LJ force and possibly the potential,
767 only relevant when force or potential switching is used
772 distance for the LJ or Buckingham cut-off
778 don't apply any correction
780 .. mdp-value:: EnerPres
782 apply long range dispersion corrections for Energy and Pressure
786 apply long range dispersion corrections for Energy only
792 .. mdp:: table-extension
795 Extension of the non-bonded potential lookup tables beyond the
796 largest cut-off distance. With actual non-bonded interactions
797 the tables are never accessed beyond the cut-off. But a longer
798 table length might be needed for the 1-4 interactions, which
799 are always tabulated irrespective of the use of tables for
800 the non-bonded interactions.
802 .. mdp:: energygrp-table
804 Currently unsupported.
805 When user tables are used for electrostatics and/or VdW, here one
806 can give pairs of energy groups for which seperate user tables
807 should be used. The two energy groups will be appended to the table
808 file name, in order of their definition in :mdp:`energygrps`,
809 seperated by underscores. For example, if ``energygrps = Na Cl
810 Sol`` and ``energygrp-table = Na Na Na Cl``, :ref:`gmx mdrun` will
811 read ``table_Na_Na.xvg`` and ``table_Na_Cl.xvg`` in addition to the
812 normal ``table.xvg`` which will be used for all other energy group
819 .. mdp:: fourierspacing
822 For ordinary Ewald, the ratio of the box dimensions and the spacing
823 determines a lower bound for the number of wave vectors to use in
824 each (signed) direction. For PME and P3M, that ratio determines a
825 lower bound for the number of Fourier-space grid points that will
826 be used along that axis. In all cases, the number for each
827 direction can be overridden by entering a non-zero value for that
828 :mdp:`fourier-nx` direction. For optimizing the relative load of
829 the particle-particle interactions and the mesh part of PME, it is
830 useful to know that the accuracy of the electrostatics remains
831 nearly constant when the Coulomb cut-off and the PME grid spacing
832 are scaled by the same factor. Note that this spacing can be scaled
833 up along with :mdp:`rcoulomb` by the PME tuning in :ref:`gmx mdrun`.
840 Highest magnitude of wave vectors in reciprocal space when using Ewald.
841 Grid size when using PME or P3M. These values override
842 :mdp:`fourierspacing` per direction. The best choice is powers of
843 2, 3, 5 and 7. Avoid large primes. Note that these grid sizes can
844 be reduced along with scaling up :mdp:`rcoulomb` by the PME tuning
850 Interpolation order for PME. 4 equals cubic interpolation. You
851 might try 6/8/10 when running in parallel and simultaneously
852 decrease grid dimension.
857 The relative strength of the Ewald-shifted direct potential at
858 :mdp:`rcoulomb` is given by :mdp:`ewald-rtol`. Decreasing this
859 will give a more accurate direct sum, but then you need more wave
860 vectors for the reciprocal sum.
862 .. mdp:: ewald-rtol-lj
865 When doing PME for VdW-interactions, :mdp:`ewald-rtol-lj` is used
866 to control the relative strength of the dispersion potential at
867 :mdp:`rvdw` in the same way as :mdp:`ewald-rtol` controls the
868 electrostatic potential.
870 .. mdp:: lj-pme-comb-rule
873 The combination rules used to combine VdW-parameters in the
874 reciprocal part of LJ-PME. Geometric rules are much faster than
875 Lorentz-Berthelot and usually the recommended choice, even when the
876 rest of the force field uses the Lorentz-Berthelot rules.
878 .. mdp-value:: Geometric
880 Apply geometric combination rules
882 .. mdp-value:: Lorentz-Berthelot
884 Apply Lorentz-Berthelot combination rules
886 .. mdp:: ewald-geometry
890 The Ewald sum is performed in all three dimensions.
894 The reciprocal sum is still performed in 3D, but a force and
895 potential correction applied in the `z` dimension to produce a
896 pseudo-2D summation. If your system has a slab geometry in the
897 `x-y` plane you can try to increase the `z`-dimension of the box
898 (a box height of 3 times the slab height is usually ok) and use
901 .. mdp:: epsilon-surface
904 This controls the dipole correction to the Ewald summation in
905 3D. The default value of zero means it is turned off. Turn it on by
906 setting it to the value of the relative permittivity of the
907 imaginary surface around your infinite system. Be careful - you
908 shouldn't use this if you have free mobile charges in your
909 system. This value does not affect the slab 3DC variant of the long
920 No temperature coupling.
922 .. mdp-value:: berendsen
924 Temperature coupling with a Berendsen thermostat to a bath with
925 temperature :mdp:`ref-t`, with time constant
926 :mdp:`tau-t`. Several groups can be coupled separately, these
927 are specified in the :mdp:`tc-grps` field separated by spaces.
929 .. mdp-value:: nose-hoover
931 Temperature coupling using a Nose-Hoover extended ensemble. The
932 reference temperature and coupling groups are selected as above,
933 but in this case :mdp:`tau-t` controls the period of the
934 temperature fluctuations at equilibrium, which is slightly
935 different from a relaxation time. For NVT simulations the
936 conserved energy quantity is written to the energy and log files.
938 .. mdp-value:: andersen
940 Temperature coupling by randomizing a fraction of the particle velocities
941 at each timestep. Reference temperature and coupling groups are
942 selected as above. :mdp:`tau-t` is the average time between
943 randomization of each molecule. Inhibits particle dynamics
944 somewhat, but little or no ergodicity issues. Currently only
945 implemented with velocity Verlet, and not implemented with
948 .. mdp-value:: andersen-massive
950 Temperature coupling by randomizing velocities of all particles at
951 infrequent timesteps. Reference temperature and coupling groups are
952 selected as above. :mdp:`tau-t` is the time between
953 randomization of all molecules. Inhibits particle dynamics
954 somewhat, but little or no ergodicity issues. Currently only
955 implemented with velocity Verlet.
957 .. mdp-value:: v-rescale
959 Temperature coupling using velocity rescaling with a stochastic
960 term (JCP 126, 014101). This thermostat is similar to Berendsen
961 coupling, with the same scaling using :mdp:`tau-t`, but the
962 stochastic term ensures that a proper canonical ensemble is
963 generated. The random seed is set with :mdp:`ld-seed`. This
964 thermostat works correctly even for :mdp:`tau-t` =0. For NVT
965 simulations the conserved energy quantity is written to the
971 The frequency for coupling the temperature. The default value of -1
972 sets :mdp:`nsttcouple` equal to :mdp:`nstlist`, unless
973 :mdp:`nstlist` <=0, then a value of 10 is used. For velocity
974 Verlet integrators :mdp:`nsttcouple` is set to 1.
976 .. mdp:: nh-chain-length
979 The number of chained Nose-Hoover thermostats for velocity Verlet
980 integrators, the leap-frog :mdp-value:`integrator=md` integrator
981 only supports 1. Data for the NH chain variables is not printed
982 to the :ref:`edr` file by default, but can be turned on with the
983 :mdp:`print-nose-hoover-chain-variables` option.
985 .. mdp:: print-nose-hoover-chain-variables
989 Do not store Nose-Hoover chain variables in the energy file.
993 Store all positions and velocities of the Nose-Hoover chain
998 groups to couple to separate temperature baths
1003 time constant for coupling (one for each group in
1004 :mdp:`tc-grps`), -1 means no temperature coupling
1009 reference temperature for coupling (one for each group in
1020 No pressure coupling. This means a fixed box size.
1022 .. mdp-value:: Berendsen
1024 Exponential relaxation pressure coupling with time constant
1025 :mdp:`tau-p`. The box is scaled every :mdp:`nstpcouple` steps. It has been
1026 argued that this does not yield a correct thermodynamic
1027 ensemble, but it is the most efficient way to scale a box at the
1030 .. mdp-value:: Parrinello-Rahman
1032 Extended-ensemble pressure coupling where the box vectors are
1033 subject to an equation of motion. The equation of motion for the
1034 atoms is coupled to this. No instantaneous scaling takes
1035 place. As for Nose-Hoover temperature coupling the time constant
1036 :mdp:`tau-p` is the period of pressure fluctuations at
1037 equilibrium. This is probably a better method when you want to
1038 apply pressure scaling during data collection, but beware that
1039 you can get very large oscillations if you are starting from a
1040 different pressure. For simulations where the exact fluctations
1041 of the NPT ensemble are important, or if the pressure coupling
1042 time is very short it may not be appropriate, as the previous
1043 time step pressure is used in some steps of the |Gromacs|
1044 implementation for the current time step pressure.
1048 Martyna-Tuckerman-Tobias-Klein implementation, only useable with
1049 :mdp-value:`integrator=md-vv` or :mdp-value:`integrator=md-vv-avek`, very similar to
1050 Parrinello-Rahman. As for Nose-Hoover temperature coupling the
1051 time constant :mdp:`tau-p` is the period of pressure
1052 fluctuations at equilibrium. This is probably a better method
1053 when you want to apply pressure scaling during data collection,
1054 but beware that you can get very large oscillations if you are
1055 starting from a different pressure. Currently (as of version
1056 5.1), it only supports isotropic scaling, and only works without
1061 Specifies the kind of isotropy of the pressure coupling used. Each
1062 kind takes one or more values for :mdp:`compressibility` and
1063 :mdp:`ref-p`. Only a single value is permitted for :mdp:`tau-p`.
1065 .. mdp-value:: isotropic
1067 Isotropic pressure coupling with time constant
1068 :mdp:`tau-p`. One value each for :mdp:`compressibility` and
1069 :mdp:`ref-p` is required.
1071 .. mdp-value:: semiisotropic
1073 Pressure coupling which is isotropic in the ``x`` and ``y``
1074 direction, but different in the ``z`` direction. This can be
1075 useful for membrane simulations. Two values each for
1076 :mdp:`compressibility` and :mdp:`ref-p` are required, for
1077 ``x/y`` and ``z`` directions respectively.
1079 .. mdp-value:: anisotropic
1081 Same as before, but 6 values are needed for ``xx``, ``yy``, ``zz``,
1082 ``xy/yx``, ``xz/zx`` and ``yz/zy`` components,
1083 respectively. When the off-diagonal compressibilities are set to
1084 zero, a rectangular box will stay rectangular. Beware that
1085 anisotropic scaling can lead to extreme deformation of the
1088 .. mdp-value:: surface-tension
1090 Surface tension coupling for surfaces parallel to the
1091 xy-plane. Uses normal pressure coupling for the `z`-direction,
1092 while the surface tension is coupled to the `x/y` dimensions of
1093 the box. The first :mdp:`ref-p` value is the reference surface
1094 tension times the number of surfaces ``bar nm``, the second
1095 value is the reference `z`-pressure ``bar``. The two
1096 :mdp:`compressibility` values are the compressibility in the
1097 `x/y` and `z` direction respectively. The value for the
1098 `z`-compressibility should be reasonably accurate since it
1099 influences the convergence of the surface-tension, it can also
1100 be set to zero to have a box with constant height.
1105 The frequency for coupling the pressure. The default value of -1
1106 sets :mdp:`nstpcouple` equal to :mdp:`nstlist`, unless
1107 :mdp:`nstlist` <=0, then a value of 10 is used. For velocity
1108 Verlet integrators :mdp:`nstpcouple` is set to 1.
1113 The time constant for pressure coupling (one value for all
1116 .. mdp:: compressibility
1119 The compressibility (NOTE: this is now really in bar\ :sup:`-1`) For water at 1
1120 atm and 300 K the compressibility is 4.5e-5 bar\ :sup:`-1`. The number of
1121 required values is implied by :mdp:`pcoupltype`.
1126 The reference pressure for coupling. The number of required values
1127 is implied by :mdp:`pcoupltype`.
1129 .. mdp:: refcoord-scaling
1133 The reference coordinates for position restraints are not
1134 modified. Note that with this option the virial and pressure
1135 might be ill defined, see :ref:`here <reference-manual-position-restraints>`
1140 The reference coordinates are scaled with the scaling matrix of
1141 the pressure coupling.
1145 Scale the center of mass of the reference coordinates with the
1146 scaling matrix of the pressure coupling. The vectors of each
1147 reference coordinate to the center of mass are not scaled. Only
1148 one COM is used, even when there are multiple molecules with
1149 position restraints. For calculating the COM of the reference
1150 coordinates in the starting configuration, periodic boundary
1151 conditions are not taken into account. Note that with this option
1152 the virial and pressure might be ill defined, see
1153 :ref:`here <reference-manual-position-restraints>` for more details.
1159 Simulated annealing is controlled separately for each temperature
1160 group in |Gromacs|. The reference temperature is a piecewise linear
1161 function, but you can use an arbitrary number of points for each
1162 group, and choose either a single sequence or a periodic behaviour for
1163 each group. The actual annealing is performed by dynamically changing
1164 the reference temperature used in the thermostat algorithm selected,
1165 so remember that the system will usually not instantaneously reach the
1166 reference temperature!
1170 Type of annealing for each temperature group
1174 No simulated annealing - just couple to reference temperature value.
1176 .. mdp-value:: single
1178 A single sequence of annealing points. If your simulation is
1179 longer than the time of the last point, the temperature will be
1180 coupled to this constant value after the annealing sequence has
1181 reached the last time point.
1183 .. mdp-value:: periodic
1185 The annealing will start over at the first reference point once
1186 the last reference time is reached. This is repeated until the
1189 .. mdp:: annealing-npoints
1191 A list with the number of annealing reference/control points used
1192 for each temperature group. Use 0 for groups that are not
1193 annealed. The number of entries should equal the number of
1196 .. mdp:: annealing-time
1198 List of times at the annealing reference/control points for each
1199 group. If you are using periodic annealing, the times will be used
1200 modulo the last value, *i.e.* if the values are 0, 5, 10, and 15,
1201 the coupling will restart at the 0ps value after 15ps, 30ps, 45ps,
1202 etc. The number of entries should equal the sum of the numbers
1203 given in :mdp:`annealing-npoints`.
1205 .. mdp:: annealing-temp
1207 List of temperatures at the annealing reference/control points for
1208 each group. The number of entries should equal the sum of the
1209 numbers given in :mdp:`annealing-npoints`.
1211 Confused? OK, let's use an example. Assume you have two temperature
1212 groups, set the group selections to ``annealing = single periodic``,
1213 the number of points of each group to ``annealing-npoints = 3 4``, the
1214 times to ``annealing-time = 0 3 6 0 2 4 6`` and finally temperatures
1215 to ``annealing-temp = 298 280 270 298 320 320 298``. The first group
1216 will be coupled to 298K at 0ps, but the reference temperature will
1217 drop linearly to reach 280K at 3ps, and then linearly between 280K and
1218 270K from 3ps to 6ps. After this is stays constant, at 270K. The
1219 second group is coupled to 298K at 0ps, it increases linearly to 320K
1220 at 2ps, where it stays constant until 4ps. Between 4ps and 6ps it
1221 decreases to 298K, and then it starts over with the same pattern
1222 again, *i.e.* rising linearly from 298K to 320K between 6ps and
1223 8ps. Check the summary printed by :ref:`gmx grompp` if you are unsure!
1233 Do not generate velocities. The velocities are set to zero
1234 when there are no velocities in the input structure file.
1238 Generate velocities in :ref:`gmx grompp` according to a
1239 Maxwell distribution at temperature :mdp:`gen-temp`, with
1240 random seed :mdp:`gen-seed`. This is only meaningful with
1241 :mdp-value:`integrator=md`.
1246 temperature for Maxwell distribution
1251 used to initialize random generator for random velocities,
1252 when :mdp:`gen-seed` is set to -1, a pseudo random seed is
1259 .. mdp:: constraints
1261 Controls which bonds in the topology will be converted to rigid
1262 holonomic constraints. Note that typical rigid water models do not
1263 have bonds, but rather a specialized ``[settles]`` directive, so
1264 are not affected by this keyword.
1268 No bonds converted to constraints.
1270 .. mdp-value:: h-bonds
1272 Convert the bonds with H-atoms to constraints.
1274 .. mdp-value:: all-bonds
1276 Convert all bonds to constraints.
1278 .. mdp-value:: h-angles
1280 Convert all bonds to constraints and convert the angles that
1281 involve H-atoms to bond-constraints.
1283 .. mdp-value:: all-angles
1285 Convert all bonds to constraints and all angles to bond-constraints.
1287 .. mdp:: constraint-algorithm
1289 Chooses which solver satisfies any non-SETTLE holonomic
1292 .. mdp-value:: LINCS
1294 LINear Constraint Solver. With domain decomposition the parallel
1295 version P-LINCS is used. The accuracy in set with
1296 :mdp:`lincs-order`, which sets the number of matrices in the
1297 expansion for the matrix inversion. After the matrix inversion
1298 correction the algorithm does an iterative correction to
1299 compensate for lengthening due to rotation. The number of such
1300 iterations can be controlled with :mdp:`lincs-iter`. The root
1301 mean square relative constraint deviation is printed to the log
1302 file every :mdp:`nstlog` steps. If a bond rotates more than
1303 :mdp:`lincs-warnangle` in one step, a warning will be printed
1304 both to the log file and to ``stderr``. LINCS should not be used
1305 with coupled angle constraints.
1307 .. mdp-value:: SHAKE
1309 SHAKE is slightly slower and less stable than LINCS, but does
1310 work with angle constraints. The relative tolerance is set with
1311 :mdp:`shake-tol`, 0.0001 is a good value for "normal" MD. SHAKE
1312 does not support constraints between atoms on different
1313 decomposition domains, so it can only be used with domain
1314 decomposition when so-called update-groups are used, which is
1315 usally the case when only bonds involving hydrogens are
1316 constrained. SHAKE can not be used with energy minimization.
1318 .. mdp:: continuation
1320 This option was formerly known as ``unconstrained-start``.
1324 apply constraints to the start configuration and reset shells
1328 do not apply constraints to the start configuration and do not
1329 reset shells, useful for exact coninuation and reruns
1334 relative tolerance for SHAKE
1336 .. mdp:: lincs-order
1339 Highest order in the expansion of the constraint coupling
1340 matrix. When constraints form triangles, an additional expansion of
1341 the same order is applied on top of the normal expansion only for
1342 the couplings within such triangles. For "normal" MD simulations an
1343 order of 4 usually suffices, 6 is needed for large time-steps with
1344 virtual sites or BD. For accurate energy minimization an order of 8
1345 or more might be required. With domain decomposition, the cell size
1346 is limited by the distance spanned by :mdp:`lincs-order` +1
1347 constraints. When one wants to scale further than this limit, one
1348 can decrease :mdp:`lincs-order` and increase :mdp:`lincs-iter`,
1349 since the accuracy does not deteriorate when (1+ :mdp:`lincs-iter`
1350 )* :mdp:`lincs-order` remains constant.
1355 Number of iterations to correct for rotational lengthening in
1356 LINCS. For normal runs a single step is sufficient, but for NVE
1357 runs where you want to conserve energy accurately or for accurate
1358 energy minimization you might want to increase it to 2.
1360 .. mdp:: lincs-warnangle
1363 maximum angle that a bond can rotate before LINCS will complain
1369 bonds are represented by a harmonic potential
1373 bonds are represented by a Morse potential
1376 Energy group exclusions
1377 ^^^^^^^^^^^^^^^^^^^^^^^
1379 .. mdp:: energygrp-excl
1381 Pairs of energy groups for which all non-bonded interactions are
1382 excluded. An example: if you have two energy groups ``Protein`` and
1383 ``SOL``, specifying ``energygrp-excl = Protein Protein SOL SOL``
1384 would give only the non-bonded interactions between the protein and
1385 the solvent. This is especially useful for speeding up energy
1386 calculations with ``mdrun -rerun`` and for excluding interactions
1387 within frozen groups.
1396 When set to 1 there is a wall at ``z=0``, when set to 2 there is
1397 also a wall at ``z=z-box``. Walls can only be used with :mdp:`pbc`
1398 ``=xy``. When set to 2, pressure coupling and Ewald summation can be
1399 used (it is usually best to use semiisotropic pressure coupling
1400 with the ``x/y`` compressibility set to 0, as otherwise the surface
1401 area will change). Walls interact wit the rest of the system
1402 through an optional :mdp:`wall-atomtype`. Energy groups ``wall0``
1403 and ``wall1`` (for :mdp:`nwall` =2) are added automatically to
1404 monitor the interaction of energy groups with each wall. The center
1405 of mass motion removal will be turned off in the ``z``-direction.
1407 .. mdp:: wall-atomtype
1409 the atom type name in the force field for each wall. By (for
1410 example) defining a special wall atom type in the topology with its
1411 own combination rules, this allows for independent tuning of the
1412 interaction of each atomtype with the walls.
1418 LJ integrated over the volume behind the wall: 9-3 potential
1422 LJ integrated over the wall surface: 10-4 potential
1426 direct LJ potential with the ``z`` distance from the wall
1430 user defined potentials indexed with the ``z`` distance from the
1431 wall, the tables are read analogously to the
1432 :mdp:`energygrp-table` option, where the first name is for a
1433 "normal" energy group and the second name is ``wall0`` or
1434 ``wall1``, only the dispersion and repulsion columns are used
1436 .. mdp:: wall-r-linpot
1439 Below this distance from the wall the potential is continued
1440 linearly and thus the force is constant. Setting this option to a
1441 postive value is especially useful for equilibration when some
1442 atoms are beyond a wall. When the value is <=0 (<0 for
1443 :mdp:`wall-type` =table), a fatal error is generated when atoms
1446 .. mdp:: wall-density
1448 [nm\ :sup:`-3`] / [nm\ :sup:`-2`]
1449 the number density of the atoms for each wall for wall types 9-3
1452 .. mdp:: wall-ewald-zfac
1455 The scaling factor for the third box vector for Ewald summation
1456 only, the minimum is 2. Ewald summation can only be used with
1457 :mdp:`nwall` =2, where one should use :mdp:`ewald-geometry`
1458 ``=3dc``. The empty layer in the box serves to decrease the
1459 unphysical Coulomb interaction between periodic images.
1465 Note that where pulling coordinates are applicable, there can be more
1466 than one (set with :mdp:`pull-ncoords`) and multiple related :ref:`mdp`
1467 variables will exist accordingly. Documentation references to things
1468 like :mdp:`pull-coord1-vec` should be understood to apply to to the
1469 applicable pulling coordinate, eg. the second pull coordinate is described by
1470 pull-coord2-vec, pull-coord2-k, and so on.
1476 No center of mass pulling. All the following pull options will
1477 be ignored (and if present in the :ref:`mdp` file, they unfortunately
1482 Center of mass pulling will be applied on 1 or more groups using
1483 1 or more pull coordinates.
1485 .. mdp:: pull-cylinder-r
1488 the radius of the cylinder for :mdp-value:`pull-coord1-geometry=cylinder`
1490 .. mdp:: pull-constr-tol
1493 the relative constraint tolerance for constraint pulling
1495 .. mdp:: pull-print-com
1499 do not print the COM for any group
1503 print the COM of all groups for all pull coordinates
1505 .. mdp:: pull-print-ref-value
1509 do not print the reference value for each pull coordinate
1513 print the reference value for each pull coordinate
1515 .. mdp:: pull-print-components
1519 only print the distance for each pull coordinate
1523 print the distance and Cartesian components selected in
1524 :mdp:`pull-coord1-dim`
1526 .. mdp:: pull-nstxout
1529 frequency for writing out the COMs of all the pull group (0 is
1532 .. mdp:: pull-nstfout
1535 frequency for writing out the force of all the pulled group
1538 .. mdp:: pull-pbc-ref-prev-step-com
1542 Use the reference atom (:mdp:`pull-group1-pbcatom`) for the
1543 treatment of periodic boundary conditions.
1547 Use the COM of the previous step as reference for the treatment
1548 of periodic boundary conditions. The reference is initialized
1549 using the reference atom (:mdp:`pull-group1-pbcatom`), which should
1550 be located centrally in the group. Using the COM from the
1551 previous step can be useful if one or more pull groups are large.
1553 .. mdp:: pull-xout-average
1557 Write the instantaneous coordinates for all the pulled groups.
1561 Write the average coordinates (since last output) for all the
1562 pulled groups. N.b., some analysis tools might expect instantaneous
1565 .. mdp:: pull-fout-average
1569 Write the instantaneous force for all the pulled groups.
1573 Write the average force (since last output) for all the
1574 pulled groups. N.b., some analysis tools might expect instantaneous
1577 .. mdp:: pull-ngroups
1580 The number of pull groups, not including the absolute reference
1581 group, when used. Pull groups can be reused in multiple pull
1582 coordinates. Below only the pull options for group 1 are given,
1583 further groups simply increase the group index number.
1585 .. mdp:: pull-ncoords
1588 The number of pull coordinates. Below only the pull options for
1589 coordinate 1 are given, further coordinates simply increase the
1590 coordinate index number.
1592 .. mdp:: pull-group1-name
1594 The name of the pull group, is looked up in the index file or in
1595 the default groups to obtain the atoms involved.
1597 .. mdp:: pull-group1-weights
1599 Optional relative weights which are multiplied with the masses of
1600 the atoms to give the total weight for the COM. The number should
1601 be 0, meaning all 1, or the number of atoms in the pull group.
1603 .. mdp:: pull-group1-pbcatom
1606 The reference atom for the treatment of periodic boundary
1607 conditions inside the group (this has no effect on the treatment of
1608 the pbc between groups). This option is only important when the
1609 diameter of the pull group is larger than half the shortest box
1610 vector. For determining the COM, all atoms in the group are put at
1611 their periodic image which is closest to
1612 :mdp:`pull-group1-pbcatom`. A value of 0 means that the middle
1613 atom (number wise) is used, which is only safe for small groups.
1614 :ref:`gmx grompp` checks that the maximum distance from the reference
1615 atom (specifically chosen, or not) to the other atoms in the group
1616 is not too large. This parameter is not used with
1617 :mdp:`pull-coord1-geometry` cylinder. A value of -1 turns on cosine
1618 weighting, which is useful for a group of molecules in a periodic
1619 system, *e.g.* a water slab (see Engin et al. J. Chem. Phys. B
1622 .. mdp:: pull-coord1-type
1624 .. mdp-value:: umbrella
1626 Center of mass pulling using an umbrella potential between the
1627 reference group and one or more groups.
1629 .. mdp-value:: constraint
1631 Center of mass pulling using a constraint between the reference
1632 group and one or more groups. The setup is identical to the
1633 option umbrella, except for the fact that a rigid constraint is
1634 applied instead of a harmonic potential.
1636 .. mdp-value:: constant-force
1638 Center of mass pulling using a linear potential and therefore a
1639 constant force. For this option there is no reference position
1640 and therefore the parameters :mdp:`pull-coord1-init` and
1641 :mdp:`pull-coord1-rate` are not used.
1643 .. mdp-value:: flat-bottom
1645 At distances above :mdp:`pull-coord1-init` a harmonic potential
1646 is applied, otherwise no potential is applied.
1648 .. mdp-value:: flat-bottom-high
1650 At distances below :mdp:`pull-coord1-init` a harmonic potential
1651 is applied, otherwise no potential is applied.
1653 .. mdp-value:: external-potential
1655 An external potential that needs to be provided by another
1658 .. mdp:: pull-coord1-potential-provider
1660 The name of the external module that provides the potential for
1661 the case where :mdp:`pull-coord1-type` is external-potential.
1663 .. mdp:: pull-coord1-geometry
1665 .. mdp-value:: distance
1667 Pull along the vector connecting the two groups. Components can
1668 be selected with :mdp:`pull-coord1-dim`.
1670 .. mdp-value:: direction
1672 Pull in the direction of :mdp:`pull-coord1-vec`.
1674 .. mdp-value:: direction-periodic
1676 As :mdp-value:`pull-coord1-geometry=direction`, but does not apply
1677 periodic box vector corrections to keep the distance within half
1678 the box length. This is (only) useful for pushing groups apart
1679 by more than half the box length by continuously changing the reference
1680 location using a pull rate. With this geometry the box should not be
1681 dynamic (*e.g.* no pressure scaling) in the pull dimensions and
1682 the pull force is not added to the virial.
1684 .. mdp-value:: direction-relative
1686 As :mdp-value:`pull-coord1-geometry=direction`, but the pull vector is the vector
1687 that points from the COM of a third to the COM of a fourth pull
1688 group. This means that 4 groups need to be supplied in
1689 :mdp:`pull-coord1-groups`. Note that the pull force will give
1690 rise to a torque on the pull vector, which is turn leads to
1691 forces perpendicular to the pull vector on the two groups
1692 defining the vector. If you want a pull group to move between
1693 the two groups defining the vector, simply use the union of
1694 these two groups as the reference group.
1696 .. mdp-value:: cylinder
1698 Designed for pulling with respect to a layer where the reference
1699 COM is given by a local cylindrical part of the reference group.
1700 The pulling is in the direction of :mdp:`pull-coord1-vec`. From
1701 the first of the two groups in :mdp:`pull-coord1-groups` a
1702 cylinder is selected around the axis going through the COM of
1703 the second group with direction :mdp:`pull-coord1-vec` with
1704 radius :mdp:`pull-cylinder-r`. Weights of the atoms decrease
1705 continously to zero as the radial distance goes from 0 to
1706 :mdp:`pull-cylinder-r` (mass weighting is also used). The radial
1707 dependence gives rise to radial forces on both pull groups.
1708 Note that the radius should be smaller than half the box size.
1709 For tilted cylinders they should be even smaller than half the
1710 box size since the distance of an atom in the reference group
1711 from the COM of the pull group has both a radial and an axial
1712 component. This geometry is not supported with constraint
1715 .. mdp-value:: angle
1717 Pull along an angle defined by four groups. The angle is
1718 defined as the angle between two vectors: the vector connecting
1719 the COM of the first group to the COM of the second group and
1720 the vector connecting the COM of the third group to the COM of
1723 .. mdp-value:: angle-axis
1725 As :mdp-value:`pull-coord1-geometry=angle` but the second vector is given by :mdp:`pull-coord1-vec`.
1726 Thus, only the two groups that define the first vector need to be given.
1728 .. mdp-value:: dihedral
1730 Pull along a dihedral angle defined by six groups. These pairwise
1731 define three vectors: the vector connecting the COM of group 1
1732 to the COM of group 2, the COM of group 3 to the COM of group 4,
1733 and the COM of group 5 to the COM group 6. The dihedral angle is
1734 then defined as the angle between two planes: the plane spanned by the
1735 the two first vectors and the plane spanned the two last vectors.
1738 .. mdp:: pull-coord1-groups
1740 The group indices on which this pull coordinate will operate.
1741 The number of group indices required is geometry dependent.
1742 The first index can be 0, in which case an
1743 absolute reference of :mdp:`pull-coord1-origin` is used. With an
1744 absolute reference the system is no longer translation invariant
1745 and one should think about what to do with the center of mass
1748 .. mdp:: pull-coord1-dim
1751 Selects the dimensions that this pull coordinate acts on and that
1752 are printed to the output files when
1753 :mdp:`pull-print-components` = :mdp-value:`pull-coord1-start=yes`. With
1754 :mdp:`pull-coord1-geometry` = :mdp-value:`pull-coord1-geometry=distance`, only Cartesian
1755 components set to Y contribute to the distance. Thus setting this
1756 to Y Y N results in a distance in the x/y plane. With other
1757 geometries all dimensions with non-zero entries in
1758 :mdp:`pull-coord1-vec` should be set to Y, the values for other
1759 dimensions only affect the output.
1761 .. mdp:: pull-coord1-origin
1764 The pull reference position for use with an absolute reference.
1766 .. mdp:: pull-coord1-vec
1769 The pull direction. :ref:`gmx grompp` normalizes the vector.
1771 .. mdp:: pull-coord1-start
1775 do not modify :mdp:`pull-coord1-init`
1779 add the COM distance of the starting conformation to
1780 :mdp:`pull-coord1-init`
1782 .. mdp:: pull-coord1-init
1785 The reference distance or reference angle at t=0.
1787 .. mdp:: pull-coord1-rate
1789 (0) [nm/ps] or [deg/ps]
1790 The rate of change of the reference position or reference angle.
1792 .. mdp:: pull-coord1-k
1794 (0) [kJ mol\ :sup:`-1` nm\ :sup:`-2`] or [kJ mol\ :sup:`-1` nm\ :sup:`-1`] or
1795 [kJ mol\ :sup:`-1` rad\ :sup:`-2`] or [kJ mol\ :sup:`-1` rad\ :sup:`-1`]
1796 The force constant. For umbrella pulling this is the harmonic force
1797 constant in kJ mol\ :sup:`-1` nm\ :sup:`-2` (or kJ mol\ :sup:`-1` rad\ :sup:`-2`
1798 for angles). For constant force pulling this is the
1799 force constant of the linear potential, and thus the negative (!)
1800 of the constant force in kJ mol\ :sup:`-1` nm\ :sup:`-1`
1801 (or kJ mol\ :sup:`-1` rad\ :sup:`-1` for angles).
1802 Note that for angles the force constant is expressed in terms of radians
1803 (while :mdp:`pull-coord1-init` and :mdp:`pull-coord1-rate` are expressed in degrees).
1805 .. mdp:: pull-coord1-kB
1807 (pull-k1) [kJ mol\ :sup:`-1` nm\ :sup:`-2`] or [kJ mol\ :sup:`-1` nm\ :sup:`-1`]
1808 or [kJ mol\ :sup:`-1` rad\ :sup:`-2`] or [kJ mol\ :sup:`-1` rad\ :sup:`-1`]
1809 As :mdp:`pull-coord1-k`, but for state B. This is only used when
1810 :mdp:`free-energy` is turned on. The force constant is then (1 -
1811 lambda) * :mdp:`pull-coord1-k` + lambda * :mdp:`pull-coord1-kB`.
1813 AWH adaptive biasing
1814 ^^^^^^^^^^^^^^^^^^^^
1824 Adaptively bias a reaction coordinate using the AWH method and estimate
1825 the corresponding PMF. The PMF and other AWH data are written to energy
1826 file at an interval set by :mdp:`awh-nstout` and can be extracted with
1827 the ``gmx awh`` tool. The AWH coordinate can be
1828 multidimensional and is defined by mapping each dimension to a pull coordinate index.
1829 This is only allowed if :mdp-value:`pull-coord1-type=external-potential` and
1830 :mdp:`pull-coord1-potential-provider` = ``awh`` for the concerned pull coordinate
1831 indices. Pull geometry 'direction-periodic' is not supported by AWH.
1833 .. mdp:: awh-potential
1835 .. mdp-value:: convolved
1837 The applied biasing potential is the convolution of the bias function and a
1838 set of harmonic umbrella potentials (see :mdp-value:`awh-potential=umbrella` below). This results
1839 in a smooth potential function and force. The resolution of the potential is set
1840 by the force constant of each umbrella, see :mdp:`awh1-dim1-force-constant`.
1842 .. mdp-value:: umbrella
1844 The potential bias is applied by controlling the position of an harmonic potential
1845 using Monte-Carlo sampling. The force constant is set with
1846 :mdp:`awh1-dim1-force-constant`. The umbrella location
1847 is sampled using Monte-Carlo every :mdp:`awh-nstsample` steps.
1848 There are no advantages to using an umbrella.
1849 This option is mainly for comparison and testing purposes.
1851 .. mdp:: awh-share-multisim
1855 AWH will not share biases across simulations started with
1856 :ref:`gmx mdrun` option ``-multidir``. The biases will be independent.
1860 With :ref:`gmx mdrun` and option ``-multidir`` the bias and PMF estimates
1861 for biases with :mdp:`awh1-share-group` >0 will be shared across simulations
1862 with the biases with the same :mdp:`awh1-share-group` value.
1863 The simulations should have the same AWH settings for sharing to make sense.
1864 :ref:`gmx mdrun` will check whether the simulations are technically
1865 compatible for sharing, but the user should check that bias sharing
1866 physically makes sense.
1870 (-1) Random seed for Monte-Carlo sampling the umbrella position,
1871 where -1 indicates to generate a seed. Only used with
1872 :mdp-value:`awh-potential=umbrella`.
1877 Number of steps between printing AWH data to the energy file, should be
1878 a multiple of :mdp:`nstenergy`.
1880 .. mdp:: awh-nstsample
1883 Number of steps between sampling of the coordinate value. This sampling
1884 is the basis for updating the bias and estimating the PMF and other AWH observables.
1886 .. mdp:: awh-nsamples-update
1889 The number of coordinate samples used for each AWH update.
1890 The update interval in steps is :mdp:`awh-nstsample` times this value.
1895 The number of biases, each acting on its own coordinate.
1896 The following options should be specified
1897 for each bias although below only the options for bias number 1 is shown. Options for
1898 other bias indices are obtained by replacing '1' by the bias index.
1900 .. mdp:: awh1-error-init
1902 (10.0) [kJ mol\ :sup:`-1`]
1903 Estimated initial average error of the PMF for this bias. This value together with the
1904 given diffusion constant(s) :mdp:`awh1-dim1-diffusion` determine the initial biasing rate.
1905 The error is obviously not known *a priori*. Only a rough estimate of :mdp:`awh1-error-init`
1907 As a general guideline, leave :mdp:`awh1-error-init` to its default value when starting a new
1908 simulation. On the other hand, when there is *a priori* knowledge of the PMF (e.g. when
1909 an initial PMF estimate is provided, see the :mdp:`awh1-user-data` option)
1910 then :mdp:`awh1-error-init` should reflect that knowledge.
1912 .. mdp:: awh1-growth
1914 .. mdp-value:: exp-linear
1916 Each bias keeps a reference weight histogram for the coordinate samples.
1917 Its size sets the magnitude of the bias function and free energy estimate updates
1918 (few samples corresponds to large updates and vice versa).
1919 Thus, its growth rate sets the maximum convergence rate.
1920 By default, there is an initial stage in which the histogram grows close to exponentially (but slower than the sampling rate).
1921 In the final stage that follows, the growth rate is linear and equal to the sampling rate (set by :mdp:`awh-nstsample`).
1922 The initial stage is typically necessary for efficient convergence when starting a new simulation where
1923 high free energy barriers have not yet been flattened by the bias.
1925 .. mdp-value:: linear
1927 As :mdp-value:`awh1-growth=exp-linear` but skip the initial stage. This may be useful if there is *a priori*
1928 knowledge (see :mdp:`awh1-error-init`) which eliminates the need for an initial stage. This is also
1929 the setting compatible with :mdp-value:`awh1-target=local-boltzmann`.
1931 .. mdp:: awh1-equilibrate-histogram
1935 Do not equilibrate histogram.
1939 Before entering the initial stage (see :mdp-value:`awh1-growth=exp-linear`), make sure the
1940 histogram of sampled weights is following the target distribution closely enough (specifically,
1941 at least 80% of the target region needs to have a local relative error of less than 20%). This
1942 option would typically only be used when :mdp:`awh1-share-group` > 0
1943 and the initial configurations poorly represent the target
1946 .. mdp:: awh1-target
1948 .. mdp-value:: constant
1950 The bias is tuned towards a constant (uniform) coordinate distribution
1951 in the defined sampling interval (defined by [:mdp:`awh1-dim1-start`, :mdp:`awh1-dim1-end`]).
1953 .. mdp-value:: cutoff
1955 Similar to :mdp-value:`awh1-target=constant`, but the target
1956 distribution is proportional to 1/(1 + exp(F - :mdp-value:`awh1-target=cutoff`)),
1957 where F is the free energy relative to the estimated global minimum.
1958 This provides a smooth switch of a flat target distribution in
1959 regions with free energy lower than the cut-off to a Boltzmann
1960 distribution in regions with free energy higher than the cut-off.
1962 .. mdp-value:: boltzmann
1964 The target distribution is a Boltzmann distribtution with a scaled beta (inverse temperature)
1965 factor given by :mdp:`awh1-target-beta-scaling`. *E.g.*, a value of 0.1
1966 would give the same coordinate distribution as sampling with a simulation temperature
1969 .. mdp-value:: local-boltzmann
1971 Same target distribution and use of :mdp:`awh1-target-beta-scaling`
1972 but the convergence towards the target distribution is inherently local *i.e.*, the rate of
1973 change of the bias only depends on the local sampling. This local convergence property is
1974 only compatible with :mdp-value:`awh1-growth=linear`, since for
1975 :mdp-value:`awh1-growth=exp-linear` histograms are globally rescaled in the initial stage.
1977 .. mdp:: awh1-target-beta-scaling
1980 For :mdp-value:`awh1-target=boltzmann` and :mdp-value:`awh1-target=local-boltzmann`
1981 it is the unitless beta scaling factor taking values in (0,1).
1983 .. mdp:: awh1-target-cutoff
1985 (0) [kJ mol\ :sup:`-1`]
1986 For :mdp-value:`awh1-target=cutoff` this is the cutoff, should be > 0.
1988 .. mdp:: awh1-user-data
1992 Initialize the PMF and target distribution with default values.
1996 Initialize the PMF and target distribution with user provided data. For :mdp:`awh-nbias` = 1,
1997 :ref:`gmx mdrun` will expect a file ``awhinit.xvg`` to be present in the run directory.
1998 For multiple biases, :ref:`gmx mdrun` expects files ``awhinit1.xvg``, ``awhinit2.xvg``, etc.
1999 The file name can be changed with the ``-awh`` option.
2000 The first :mdp:`awh1-ndim` columns of
2001 each input file should contain the coordinate values, such that each row defines a point in
2002 coordinate space. Column :mdp:`awh1-ndim` + 1 should contain the PMF value for each point.
2003 The target distribution column can either follow the PMF (column :mdp:`awh1-ndim` + 2) or
2004 be in the same column as written by :ref:`gmx awh`.
2006 .. mdp:: awh1-share-group
2010 Do not share the bias.
2012 .. mdp-value:: positive
2014 Share the bias and PMF estimates within and/or between simulations.
2015 Within a simulation, the bias will be shared between biases that have the
2016 same :mdp:`awh1-share-group` index (note that the current code does not support this).
2017 With :mdp-value:`awh-share-multisim=yes` and
2018 :ref:`gmx mdrun` option ``-multidir`` the bias will also be shared across simulations.
2019 Sharing may increase convergence initially, although the starting configurations
2020 can be critical, especially when sharing between many biases.
2021 Currently, positive group values should start at 1 and increase
2022 by 1 for each subsequent bias that is shared.
2027 Number of dimensions of the coordinate, each dimension maps to 1 pull coordinate.
2028 The following options should be specified for each such dimension. Below only
2029 the options for dimension number 1 is shown. Options for other dimension indices are
2030 obtained by replacing '1' by the dimension index.
2032 .. mdp:: awh1-dim1-coord-provider
2036 The module providing the reaction coordinate for this dimension.
2037 Currently AWH can only act on pull coordinates.
2039 .. mdp:: awh1-dim1-coord-index
2042 Index of the pull coordinate defining this coordinate dimension.
2044 .. mdp:: awh1-dim1-force-constant
2046 (0) [kJ mol\ :sup:`-1` nm\ :sup:`-2`] or [kJ mol\ :sup:`-1` rad\ :sup:`-2`]
2047 Force constant for the (convolved) umbrella potential(s) along this
2048 coordinate dimension.
2050 .. mdp:: awh1-dim1-start
2053 Start value of the sampling interval along this dimension. The range of allowed
2054 values depends on the relevant pull geometry (see :mdp:`pull-coord1-geometry`).
2055 For dihedral geometries :mdp:`awh1-dim1-start` greater than :mdp:`awh1-dim1-end`
2056 is allowed. The interval will then wrap around from +period/2 to -period/2.
2057 For the direction geometry, the dimension is made periodic when
2058 the direction is along a box vector and covers more than 95%
2059 of the box length. Note that one should not apply pressure coupling
2060 along a periodic dimension.
2062 .. mdp:: awh1-dim1-end
2065 End value defining the sampling interval together with :mdp:`awh1-dim1-start`.
2067 .. mdp:: awh1-dim1-diffusion
2069 (10\ :sup:`-5`) [nm\ :sup:`2`/ps] or [rad\ :sup:`2`/ps]
2070 Estimated diffusion constant for this coordinate dimension determining the initial
2071 biasing rate. This needs only be a rough estimate and should not critically
2072 affect the results unless it is set to something very low, leading to slow convergence,
2073 or very high, forcing the system far from equilibrium. Not setting this value
2074 explicitly generates a warning.
2076 .. mdp:: awh1-dim1-cover-diameter
2079 Diameter that needs to be sampled by a single simulation around a coordinate value
2080 before the point is considered covered in the initial stage (see :mdp-value:`awh1-growth=exp-linear`).
2081 A value > 0 ensures that for each covering there is a continuous transition of this diameter
2082 across each coordinate value.
2083 This is trivially true for independent simulations but not for for multiple bias-sharing simulations
2084 (:mdp:`awh1-share-group`>0).
2085 For a diameter = 0, covering occurs as soon as the simulations have sampled the whole interval, which
2086 for many sharing simulations does not guarantee transitions across free energy barriers.
2087 On the other hand, when the diameter >= the sampling interval length, covering occurs when a single simulation
2088 has independently sampled the whole interval.
2093 These :ref:`mdp` parameters can be used enforce the rotation of a group of atoms,
2094 e.g. a protein subunit. The `reference manual`_ describes in detail 13 different potentials
2095 that can be used to achieve such a rotation.
2101 No enforced rotation will be applied. All enforced rotation options will
2102 be ignored (and if present in the :ref:`mdp` file, they unfortunately
2107 Apply the rotation potential specified by :mdp:`rot-type0` to the group of atoms given
2108 under the :mdp:`rot-group0` option.
2110 .. mdp:: rot-ngroups
2113 Number of rotation groups.
2117 Name of rotation group 0 in the index file.
2122 Type of rotation potential that is applied to rotation group 0. Can be of of the following:
2123 ``iso``, ``iso-pf``, ``pm``, ``pm-pf``, ``rm``, ``rm-pf``, ``rm2``, ``rm2-pf``,
2124 ``flex``, ``flex-t``, ``flex2``, or ``flex2-t``.
2129 Use mass weighted rotation group positions.
2134 Rotation vector, will get normalized.
2139 Pivot point for the potentials ``iso``, ``pm``, ``rm``, and ``rm2``.
2143 (0) [degree ps\ :sup:`-1`]
2144 Reference rotation rate of group 0.
2148 (0) [kJ mol\ :sup:`-1` nm\ :sup:`-2`]
2149 Force constant for group 0.
2151 .. mdp:: rot-slab-dist0
2154 Slab distance, if a flexible axis rotation type was chosen.
2156 .. mdp:: rot-min-gauss0
2159 Minimum value (cutoff) of Gaussian function for the force to be evaluated
2160 (for the flexible axis potentials).
2164 (0.0001) [nm\ :sup:`2`]
2165 Value of additive constant epsilon for ``rm2*`` and ``flex2*`` potentials.
2167 .. mdp:: rot-fit-method0
2170 Fitting method when determining the actual angle of a rotation group
2171 (can be one of ``rmsd``, ``norm``, or ``potential``).
2173 .. mdp:: rot-potfit-nsteps0
2176 For fit type ``potential``, the number of angular positions around the reference angle for which the
2177 rotation potential is evaluated.
2179 .. mdp:: rot-potfit-step0
2182 For fit type ``potential``, the distance in degrees between two angular positions.
2184 .. mdp:: rot-nstrout
2187 Output frequency (in steps) for the angle of the rotation group, as well as for the torque
2188 and the rotation potential energy.
2190 .. mdp:: rot-nstsout
2193 Output frequency for per-slab data of the flexible axis potentials, i.e. angles, torques and slab centers.
2203 ignore distance restraint information in topology file
2205 .. mdp-value:: simple
2207 simple (per-molecule) distance restraints.
2209 .. mdp-value:: ensemble
2211 distance restraints over an ensemble of molecules in one
2212 simulation box. Normally, one would perform ensemble averaging
2213 over multiple simulations, using ``mdrun
2214 -multidir``. The environment
2215 variable ``GMX_DISRE_ENSEMBLE_SIZE`` sets the number of systems
2216 within each ensemble (usually equal to the number of directories
2217 supplied to ``mdrun -multidir``).
2219 .. mdp:: disre-weighting
2221 .. mdp-value:: equal
2223 divide the restraint force equally over all atom pairs in the
2226 .. mdp-value:: conservative
2228 the forces are the derivative of the restraint potential, this
2229 results in an weighting of the atom pairs to the reciprocal
2230 seventh power of the displacement. The forces are conservative
2231 when :mdp:`disre-tau` is zero.
2233 .. mdp:: disre-mixed
2237 the violation used in the calculation of the restraint force is
2238 the time-averaged violation
2242 the violation used in the calculation of the restraint force is
2243 the square root of the product of the time-averaged violation
2244 and the instantaneous violation
2248 (1000) [kJ mol\ :sup:`-1` nm\ :sup:`-2`]
2249 force constant for distance restraints, which is multiplied by a
2250 (possibly) different factor for each restraint given in the `fac`
2251 column of the interaction in the topology file.
2256 time constant for distance restraints running average. A value of
2257 zero turns off time averaging.
2259 .. mdp:: nstdisreout
2262 period between steps when the running time-averaged and
2263 instantaneous distances of all atom pairs involved in restraints
2264 are written to the energy file (can make the energy file very
2271 ignore orientation restraint information in topology file
2275 use orientation restraints, ensemble averaging can be performed
2276 with ``mdrun -multidir``
2280 (0) [kJ mol\ :sup:`-1`]
2281 force constant for orientation restraints, which is multiplied by a
2282 (possibly) different weight factor for each restraint, can be set
2283 to zero to obtain the orientations from a free simulation
2288 time constant for orientation restraints running average. A value
2289 of zero turns off time averaging.
2291 .. mdp:: orire-fitgrp
2293 fit group for orientation restraining. This group of atoms is used
2294 to determine the rotation **R** of the system with respect to the
2295 reference orientation. The reference orientation is the starting
2296 conformation of the first subsystem. For a protein, backbone is a
2299 .. mdp:: nstorireout
2302 period between steps when the running time-averaged and
2303 instantaneous orientations for all restraints, and the molecular
2304 order tensor are written to the energy file (can make the energy
2308 Free energy calculations
2309 ^^^^^^^^^^^^^^^^^^^^^^^^
2311 .. mdp:: free-energy
2315 Only use topology A.
2319 Interpolate between topology A (lambda=0) to topology B
2320 (lambda=1) and write the derivative of the Hamiltonian with
2321 respect to lambda (as specified with :mdp:`dhdl-derivatives`),
2322 or the Hamiltonian differences with respect to other lambda
2323 values (as specified with foreign lambda) to the energy file
2324 and/or to ``dhdl.xvg``, where they can be processed by, for
2325 example :ref:`gmx bar`. The potentials, bond-lengths and angles
2326 are interpolated linearly as described in the manual. When
2327 :mdp:`sc-alpha` is larger than zero, soft-core potentials are
2328 used for the LJ and Coulomb interactions.
2332 Turns on expanded ensemble simulation, where the alchemical state
2333 becomes a dynamic variable, allowing jumping between different
2334 Hamiltonians. See the expanded ensemble options for controlling how
2335 expanded ensemble simulations are performed. The different
2336 Hamiltonians used in expanded ensemble simulations are defined by
2337 the other free energy options.
2339 .. mdp:: init-lambda
2342 starting value for lambda (float). Generally, this should only be
2343 used with slow growth (*i.e.* nonzero :mdp:`delta-lambda`). In
2344 other cases, :mdp:`init-lambda-state` should be specified
2345 instead. Must be greater than or equal to 0.
2347 .. mdp:: delta-lambda
2350 increment per time step for lambda
2352 .. mdp:: init-lambda-state
2355 starting value for the lambda state (integer). Specifies which
2356 columm of the lambda vector (:mdp:`coul-lambdas`,
2357 :mdp:`vdw-lambdas`, :mdp:`bonded-lambdas`,
2358 :mdp:`restraint-lambdas`, :mdp:`mass-lambdas`,
2359 :mdp:`temperature-lambdas`, :mdp:`fep-lambdas`) should be
2360 used. This is a zero-based index: :mdp:`init-lambda-state` 0 means
2361 the first column, and so on.
2363 .. mdp:: fep-lambdas
2366 Zero, one or more lambda values for which Delta H values will be
2367 determined and written to dhdl.xvg every :mdp:`nstdhdl`
2368 steps. Values must be between 0 and 1. Free energy differences
2369 between different lambda values can then be determined with
2370 :ref:`gmx bar`. :mdp:`fep-lambdas` is different from the
2371 other -lambdas keywords because all components of the lambda vector
2372 that are not specified will use :mdp:`fep-lambdas` (including
2373 :mdp:`restraint-lambdas` and therefore the pull code restraints).
2375 .. mdp:: coul-lambdas
2378 Zero, one or more lambda values for which Delta H values will be
2379 determined and written to dhdl.xvg every :mdp:`nstdhdl`
2380 steps. Values must be between 0 and 1. Only the electrostatic
2381 interactions are controlled with this component of the lambda
2382 vector (and only if the lambda=0 and lambda=1 states have differing
2383 electrostatic interactions).
2385 .. mdp:: vdw-lambdas
2388 Zero, one or more lambda values for which Delta H values will be
2389 determined and written to dhdl.xvg every :mdp:`nstdhdl`
2390 steps. Values must be between 0 and 1. Only the van der Waals
2391 interactions are controlled with this component of the lambda
2394 .. mdp:: bonded-lambdas
2397 Zero, one or more lambda values for which Delta H values will be
2398 determined and written to dhdl.xvg every :mdp:`nstdhdl`
2399 steps. Values must be between 0 and 1. Only the bonded interactions
2400 are controlled with this component of the lambda vector.
2402 .. mdp:: restraint-lambdas
2405 Zero, one or more lambda values for which Delta H values will be
2406 determined and written to dhdl.xvg every :mdp:`nstdhdl`
2407 steps. Values must be between 0 and 1. Only the restraint
2408 interactions: dihedral restraints, and the pull code restraints are
2409 controlled with this component of the lambda vector.
2411 .. mdp:: mass-lambdas
2414 Zero, one or more lambda values for which Delta H values will be
2415 determined and written to dhdl.xvg every :mdp:`nstdhdl`
2416 steps. Values must be between 0 and 1. Only the particle masses are
2417 controlled with this component of the lambda vector.
2419 .. mdp:: temperature-lambdas
2422 Zero, one or more lambda values for which Delta H values will be
2423 determined and written to dhdl.xvg every :mdp:`nstdhdl`
2424 steps. Values must be between 0 and 1. Only the temperatures
2425 controlled with this component of the lambda vector. Note that
2426 these lambdas should not be used for replica exchange, only for
2427 simulated tempering.
2429 .. mdp:: calc-lambda-neighbors
2432 Controls the number of lambda values for which Delta H values will
2433 be calculated and written out, if :mdp:`init-lambda-state` has
2434 been set. A positive value will limit the number of lambda points
2435 calculated to only the nth neighbors of :mdp:`init-lambda-state`:
2436 for example, if :mdp:`init-lambda-state` is 5 and this parameter
2437 has a value of 2, energies for lambda points 3-7 will be calculated
2438 and writen out. A value of -1 means all lambda points will be
2439 written out. For normal BAR such as with :ref:`gmx bar`, a value of
2440 1 is sufficient, while for MBAR -1 should be used.
2445 the soft-core alpha parameter, a value of 0 results in linear
2446 interpolation of the LJ and Coulomb interactions
2451 power 6 for the radial term in the soft-core equation.
2454 (deprecated) power 48 for the radial term in the soft-core equation.
2455 Note that sc-alpha should generally be much lower (between 0.001 and 0.003).
2460 Whether to apply the soft-core free energy interaction
2461 transformation to the Columbic interaction of a molecule. Default
2462 is no, as it is generally more efficient to turn off the Coulomic
2463 interactions linearly before turning off the van der Waals
2464 interactions. Note that it is only taken into account when lambda
2465 states are used, not with :mdp:`couple-lambda0` /
2466 :mdp:`couple-lambda1`, and you can still turn off soft-core
2467 interactions by setting :mdp:`sc-alpha` to 0.
2472 the power for lambda in the soft-core function, only the values 1
2478 the soft-core sigma for particles which have a C6 or C12 parameter
2479 equal to zero or a sigma smaller than :mdp:`sc-sigma`
2481 .. mdp:: couple-moltype
2483 Here one can supply a molecule type (as defined in the topology)
2484 for calculating solvation or coupling free energies. There is a
2485 special option ``system`` that couples all molecule types in the
2486 system. This can be useful for equilibrating a system starting from
2487 (nearly) random coordinates. :mdp:`free-energy` has to be turned
2488 on. The Van der Waals interactions and/or charges in this molecule
2489 type can be turned on or off between lambda=0 and lambda=1,
2490 depending on the settings of :mdp:`couple-lambda0` and
2491 :mdp:`couple-lambda1`. If you want to decouple one of several
2492 copies of a molecule, you need to copy and rename the molecule
2493 definition in the topology.
2495 .. mdp:: couple-lambda0
2497 .. mdp-value:: vdw-q
2499 all interactions are on at lambda=0
2503 the charges are zero (no Coulomb interactions) at lambda=0
2507 the Van der Waals interactions are turned at lambda=0; soft-core
2508 interactions will be required to avoid singularities
2512 the Van der Waals interactions are turned off and the charges
2513 are zero at lambda=0; soft-core interactions will be required to
2514 avoid singularities.
2516 .. mdp:: couple-lambda1
2518 analogous to :mdp:`couple-lambda1`, but for lambda=1
2520 .. mdp:: couple-intramol
2524 All intra-molecular non-bonded interactions for moleculetype
2525 :mdp:`couple-moltype` are replaced by exclusions and explicit
2526 pair interactions. In this manner the decoupled state of the
2527 molecule corresponds to the proper vacuum state without
2528 periodicity effects.
2532 The intra-molecular Van der Waals and Coulomb interactions are
2533 also turned on/off. This can be useful for partitioning
2534 free-energies of relatively large molecules, where the
2535 intra-molecular non-bonded interactions might lead to
2536 kinetically trapped vacuum conformations. The 1-4 pair
2537 interactions are not turned off.
2542 the frequency for writing dH/dlambda and possibly Delta H to
2543 dhdl.xvg, 0 means no ouput, should be a multiple of
2544 :mdp:`nstcalcenergy`.
2546 .. mdp:: dhdl-derivatives
2550 If yes (the default), the derivatives of the Hamiltonian with
2551 respect to lambda at each :mdp:`nstdhdl` step are written
2552 out. These values are needed for interpolation of linear energy
2553 differences with :ref:`gmx bar` (although the same can also be
2554 achieved with the right foreign lambda setting, that may not be as
2555 flexible), or with thermodynamic integration
2557 .. mdp:: dhdl-print-energy
2561 Include either the total or the potential energy in the dhdl
2562 file. Options are 'no', 'potential', or 'total'. This information
2563 is needed for later free energy analysis if the states of interest
2564 are at different temperatures. If all states are at the same
2565 temperature, this information is not needed. 'potential' is useful
2566 in case one is using ``mdrun -rerun`` to generate the ``dhdl.xvg``
2567 file. When rerunning from an existing trajectory, the kinetic
2568 energy will often not be correct, and thus one must compute the
2569 residual free energy from the potential alone, with the kinetic
2570 energy component computed analytically.
2572 .. mdp:: separate-dhdl-file
2576 The free energy values that are calculated (as specified with
2577 the foreign lambda and :mdp:`dhdl-derivatives` settings) are
2578 written out to a separate file, with the default name
2579 ``dhdl.xvg``. This file can be used directly with :ref:`gmx
2584 The free energy values are written out to the energy output file
2585 (``ener.edr``, in accumulated blocks at every :mdp:`nstenergy`
2586 steps), where they can be extracted with :ref:`gmx energy` or
2587 used directly with :ref:`gmx bar`.
2589 .. mdp:: dh-hist-size
2592 If nonzero, specifies the size of the histogram into which the
2593 Delta H values (specified with foreign lambda) and the derivative
2594 dH/dl values are binned, and written to ener.edr. This can be used
2595 to save disk space while calculating free energy differences. One
2596 histogram gets written for each foreign lambda and two for the
2597 dH/dl, at every :mdp:`nstenergy` step. Be aware that incorrect
2598 histogram settings (too small size or too wide bins) can introduce
2599 errors. Do not use histograms unless you're certain you need it.
2601 .. mdp:: dh-hist-spacing
2604 Specifies the bin width of the histograms, in energy units. Used in
2605 conjunction with :mdp:`dh-hist-size`. This size limits the
2606 accuracy with which free energies can be calculated. Do not use
2607 histograms unless you're certain you need it.
2610 Expanded Ensemble calculations
2611 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2613 .. mdp:: nstexpanded
2615 The number of integration steps beween attempted moves changing the
2616 system Hamiltonian in expanded ensemble simulations. Must be a
2617 multiple of :mdp:`nstcalcenergy`, but can be greater or less than
2624 No Monte Carlo in state space is performed.
2626 .. mdp-value:: metropolis-transition
2628 Uses the Metropolis weights to update the expanded ensemble
2629 weight of each state. Min{1,exp(-(beta_new u_new - beta_old
2632 .. mdp-value:: barker-transition
2634 Uses the Barker transition critera to update the expanded
2635 ensemble weight of each state i, defined by exp(-beta_new
2636 u_new)/(exp(-beta_new u_new)+exp(-beta_old u_old))
2638 .. mdp-value:: wang-landau
2640 Uses the Wang-Landau algorithm (in state space, not energy
2641 space) to update the expanded ensemble weights.
2643 .. mdp-value:: min-variance
2645 Uses the minimum variance updating method of Escobedo et al. to
2646 update the expanded ensemble weights. Weights will not be the
2647 free energies, but will rather emphasize states that need more
2648 sampling to give even uncertainty.
2650 .. mdp:: lmc-mc-move
2654 No Monte Carlo in state space is performed.
2656 .. mdp-value:: metropolis-transition
2658 Randomly chooses a new state up or down, then uses the
2659 Metropolis critera to decide whether to accept or reject:
2660 Min{1,exp(-(beta_new u_new - beta_old u_old)}
2662 .. mdp-value:: barker-transition
2664 Randomly chooses a new state up or down, then uses the Barker
2665 transition critera to decide whether to accept or reject:
2666 exp(-beta_new u_new)/(exp(-beta_new u_new)+exp(-beta_old u_old))
2668 .. mdp-value:: gibbs
2670 Uses the conditional weights of the state given the coordinate
2671 (exp(-beta_i u_i) / sum_k exp(beta_i u_i) to decide which state
2674 .. mdp-value:: metropolized-gibbs
2676 Uses the conditional weights of the state given the coordinate
2677 (exp(-beta_i u_i) / sum_k exp(beta_i u_i) to decide which state
2678 to move to, EXCLUDING the current state, then uses a rejection
2679 step to ensure detailed balance. Always more efficient that
2680 Gibbs, though only marginally so in many situations, such as
2681 when only the nearest neighbors have decent phase space
2687 random seed to use for Monte Carlo moves in state space. When
2688 :mdp:`lmc-seed` is set to -1, a pseudo random seed is us
2690 .. mdp:: mc-temperature
2692 Temperature used for acceptance/rejection for Monte Carlo moves. If
2693 not specified, the temperature of the simulation specified in the
2694 first group of :mdp:`ref-t` is used.
2699 The cutoff for the histogram of state occupancies to be reset, and
2700 the free energy incrementor to be changed from delta to delta *
2701 :mdp:`wl-scale`. If we define the Nratio = (number of samples at
2702 each histogram) / (average number of samples at each
2703 histogram). :mdp:`wl-ratio` of 0.8 means that means that the
2704 histogram is only considered flat if all Nratio > 0.8 AND
2705 simultaneously all 1/Nratio > 0.8.
2710 Each time the histogram is considered flat, then the current value
2711 of the Wang-Landau incrementor for the free energies is multiplied
2712 by :mdp:`wl-scale`. Value must be between 0 and 1.
2714 .. mdp:: init-wl-delta
2717 The initial value of the Wang-Landau incrementor in kT. Some value
2718 near 1 kT is usually most efficient, though sometimes a value of
2719 2-3 in units of kT works better if the free energy differences are
2722 .. mdp:: wl-oneovert
2725 Set Wang-Landau incrementor to scale with 1/(simulation time) in
2726 the large sample limit. There is significant evidence that the
2727 standard Wang-Landau algorithms in state space presented here
2728 result in free energies getting 'burned in' to incorrect values
2729 that depend on the initial state. when :mdp:`wl-oneovert` is true,
2730 then when the incrementor becomes less than 1/N, where N is the
2731 mumber of samples collected (and thus proportional to the data
2732 collection time, hence '1 over t'), then the Wang-Lambda
2733 incrementor is set to 1/N, decreasing every step. Once this occurs,
2734 :mdp:`wl-ratio` is ignored, but the weights will still stop
2735 updating when the equilibration criteria set in
2736 :mdp:`lmc-weights-equil` is achieved.
2738 .. mdp:: lmc-repeats
2741 Controls the number of times that each Monte Carlo swap type is
2742 performed each iteration. In the limit of large numbers of Monte
2743 Carlo repeats, then all methods converge to Gibbs sampling. The
2744 value will generally not need to be different from 1.
2746 .. mdp:: lmc-gibbsdelta
2749 Limit Gibbs sampling to selected numbers of neighboring states. For
2750 Gibbs sampling, it is sometimes inefficient to perform Gibbs
2751 sampling over all of the states that are defined. A positive value
2752 of :mdp:`lmc-gibbsdelta` means that only states plus or minus
2753 :mdp:`lmc-gibbsdelta` are considered in exchanges up and down. A
2754 value of -1 means that all states are considered. For less than 100
2755 states, it is probably not that expensive to include all states.
2757 .. mdp:: lmc-forced-nstart
2760 Force initial state space sampling to generate weights. In order to
2761 come up with reasonable initial weights, this setting allows the
2762 simulation to drive from the initial to the final lambda state,
2763 with :mdp:`lmc-forced-nstart` steps at each state before moving on
2764 to the next lambda state. If :mdp:`lmc-forced-nstart` is
2765 sufficiently long (thousands of steps, perhaps), then the weights
2766 will be close to correct. However, in most cases, it is probably
2767 better to simply run the standard weight equilibration algorithms.
2769 .. mdp:: nst-transition-matrix
2772 Frequency of outputting the expanded ensemble transition matrix. A
2773 negative number means it will only be printed at the end of the
2776 .. mdp:: symmetrized-transition-matrix
2779 Whether to symmetrize the empirical transition matrix. In the
2780 infinite limit the matrix will be symmetric, but will diverge with
2781 statistical noise for short timescales. Forced symmetrization, by
2782 using the matrix T_sym = 1/2 (T + transpose(T)), removes problems
2783 like the existence of (small magnitude) negative eigenvalues.
2785 .. mdp:: mininum-var-min
2788 The min-variance strategy (option of :mdp:`lmc-stats` is only
2789 valid for larger number of samples, and can get stuck if too few
2790 samples are used at each state. :mdp:`mininum-var-min` is the
2791 minimum number of samples that each state that are allowed before
2792 the min-variance strategy is activated if selected.
2794 .. mdp:: init-lambda-weights
2796 The initial weights (free energies) used for the expanded ensemble
2797 states. Default is a vector of zero weights. format is similar to
2798 the lambda vector settings in :mdp:`fep-lambdas`, except the
2799 weights can be any floating point number. Units are kT. Its length
2800 must match the lambda vector lengths.
2802 .. mdp:: lmc-weights-equil
2806 Expanded ensemble weights continue to be updated throughout the
2811 The input expanded ensemble weights are treated as equilibrated,
2812 and are not updated throughout the simulation.
2814 .. mdp-value:: wl-delta
2816 Expanded ensemble weight updating is stopped when the
2817 Wang-Landau incrementor falls below this value.
2819 .. mdp-value:: number-all-lambda
2821 Expanded ensemble weight updating is stopped when the number of
2822 samples at all of the lambda states is greater than this value.
2824 .. mdp-value:: number-steps
2826 Expanded ensemble weight updating is stopped when the number of
2827 steps is greater than the level specified by this value.
2829 .. mdp-value:: number-samples
2831 Expanded ensemble weight updating is stopped when the number of
2832 total samples across all lambda states is greater than the level
2833 specified by this value.
2835 .. mdp-value:: count-ratio
2837 Expanded ensemble weight updating is stopped when the ratio of
2838 samples at the least sampled lambda state and most sampled
2839 lambda state greater than this value.
2841 .. mdp:: simulated-tempering
2844 Turn simulated tempering on or off. Simulated tempering is
2845 implemented as expanded ensemble sampling with different
2846 temperatures instead of different Hamiltonians.
2848 .. mdp:: sim-temp-low
2851 Low temperature for simulated tempering.
2853 .. mdp:: sim-temp-high
2856 High temperature for simulated tempering.
2858 .. mdp:: simulated-tempering-scaling
2860 Controls the way that the temperatures at intermediate lambdas are
2861 calculated from the :mdp:`temperature-lambdas` part of the lambda
2864 .. mdp-value:: linear
2866 Linearly interpolates the temperatures using the values of
2867 :mdp:`temperature-lambdas`, *i.e.* if :mdp:`sim-temp-low`
2868 =300, :mdp:`sim-temp-high` =400, then lambda=0.5 correspond to
2869 a temperature of 350. A nonlinear set of temperatures can always
2870 be implemented with uneven spacing in lambda.
2872 .. mdp-value:: geometric
2874 Interpolates temperatures geometrically between
2875 :mdp:`sim-temp-low` and :mdp:`sim-temp-high`. The i:th state
2876 has temperature :mdp:`sim-temp-low` * (:mdp:`sim-temp-high` /
2877 :mdp:`sim-temp-low`) raised to the power of
2878 (i/(ntemps-1)). This should give roughly equal exchange for
2879 constant heat capacity, though of course things simulations that
2880 involve protein folding have very high heat capacity peaks.
2882 .. mdp-value:: exponential
2884 Interpolates temperatures exponentially between
2885 :mdp:`sim-temp-low` and :mdp:`sim-temp-high`. The i:th state
2886 has temperature :mdp:`sim-temp-low` + (:mdp:`sim-temp-high` -
2887 :mdp:`sim-temp-low`)*((exp(:mdp:`temperature-lambdas`
2888 (i))-1)/(exp(1.0)-i)).
2896 groups for constant acceleration (*e.g.* ``Protein Sol``) all atoms
2897 in groups Protein and Sol will experience constant acceleration as
2898 specified in the :mdp:`accelerate` line
2902 (0) [nm ps\ :sup:`-2`]
2903 acceleration for :mdp:`acc-grps`; x, y and z for each group
2904 (*e.g.* ``0.1 0.0 0.0 -0.1 0.0 0.0`` means that first group has
2905 constant acceleration of 0.1 nm ps\ :sup:`-2` in X direction, second group
2910 Groups that are to be frozen (*i.e.* their X, Y, and/or Z position
2911 will not be updated; *e.g.* ``Lipid SOL``). :mdp:`freezedim`
2912 specifies for which dimension(s) the freezing applies. To avoid
2913 spurious contributions to the virial and pressure due to large
2914 forces between completely frozen atoms you need to use energy group
2915 exclusions, this also saves computing time. Note that coordinates
2916 of frozen atoms are not scaled by pressure-coupling algorithms.
2920 dimensions for which groups in :mdp:`freezegrps` should be frozen,
2921 specify `Y` or `N` for X, Y and Z and for each group (*e.g.* ``Y Y
2922 N N N N`` means that particles in the first group can move only in
2923 Z direction. The particles in the second group can move in any
2926 .. mdp:: cos-acceleration
2928 (0) [nm ps\ :sup:`-2`]
2929 the amplitude of the acceleration profile for calculating the
2930 viscosity. The acceleration is in the X-direction and the magnitude
2931 is :mdp:`cos-acceleration` cos(2 pi z/boxheight). Two terms are
2932 added to the energy file: the amplitude of the velocity profile and
2937 (0 0 0 0 0 0) [nm ps\ :sup:`-1`]
2938 The velocities of deformation for the box elements: a(x) b(y) c(z)
2939 b(x) c(x) c(y). Each step the box elements for which :mdp:`deform`
2940 is non-zero are calculated as: box(ts)+(t-ts)*deform, off-diagonal
2941 elements are corrected for periodicity. The coordinates are
2942 transformed accordingly. Frozen degrees of freedom are (purposely)
2943 also transformed. The time ts is set to t at the first step and at
2944 steps at which x and v are written to trajectory to ensure exact
2945 restarts. Deformation can be used together with semiisotropic or
2946 anisotropic pressure coupling when the appropriate
2947 compressibilities are set to zero. The diagonal elements can be
2948 used to strain a solid. The off-diagonal elements can be used to
2949 shear a solid or a liquid.
2955 .. mdp:: electric-field-x
2956 .. mdp:: electric-field-y
2957 .. mdp:: electric-field-z
2959 Here you can specify an electric field that optionally can be
2960 alternating and pulsed. The general expression for the field
2961 has the form of a gaussian laser pulse:
2963 .. math:: E(t) = E_0 \exp\left[-\frac{(t-t_0)^2}{2\sigma^2}\right]\cos\left[\omega (t-t_0)\right]
2965 For example, the four parameters for direction x are set in the
2966 fields of :mdp:`electric-field-x` (and similar for ``electric-field-y``
2967 and ``electric-field-z``) like
2969 ``electric-field-x = E0 omega t0 sigma``
2971 with units (respectively) V nm\ :sup:`-1`, ps\ :sup:`-1`, ps, ps.
2973 In the special case that ``sigma = 0``, the exponential term is omitted
2974 and only the cosine term is used. If also ``omega = 0`` a static
2975 electric field is applied.
2977 Read more at :ref:`electric fields` and in ref. \ :ref:`146 <refCaleman2008a>`.
2980 Mixed quantum/classical molecular dynamics
2981 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2991 Do a QM/MM simulation. Several groups can be described at
2992 different QM levels separately. These are specified in the
2993 :mdp:`QMMM-grps` field separated by spaces. The level of *ab
2994 initio* theory at which the groups are described is specified by
2995 :mdp:`QMmethod` and :mdp:`QMbasis` Fields. Describing the
2996 groups at different levels of theory is only possible with the
2997 ONIOM QM/MM scheme, specified by :mdp:`QMMMscheme`.
3001 groups to be descibed at the QM level (works also in case of MiMiC QM/MM)
3005 .. mdp-value:: normal
3007 normal QM/MM. There can only be one :mdp:`QMMM-grps` that is
3008 modelled at the :mdp:`QMmethod` and :mdp:`QMbasis` level of
3009 *ab initio* theory. The rest of the system is described at the
3010 MM level. The QM and MM subsystems interact as follows: MM point
3011 charges are included in the QM one-electron hamiltonian and all
3012 Lennard-Jones interactions are described at the MM level.
3014 .. mdp-value:: ONIOM
3016 The interaction between the subsystem is described using the
3017 ONIOM method by Morokuma and co-workers. There can be more than
3018 one :mdp:`QMMM-grps` each modeled at a different level of QM
3019 theory (:mdp:`QMmethod` and :mdp:`QMbasis`).
3024 Method used to compute the energy and gradients on the QM
3025 atoms. Available methods are AM1, PM3, RHF, UHF, DFT, B3LYP, MP2,
3026 CASSCF, and MMVB. For CASSCF, the number of electrons and orbitals
3027 included in the active space is specified by :mdp:`CASelectrons`
3028 and :mdp:`CASorbitals`.
3033 Basis set used to expand the electronic wavefuntion. Only Gaussian
3034 basis sets are currently available, *i.e.* ``STO-3G, 3-21G, 3-21G*,
3035 3-21+G*, 6-21G, 6-31G, 6-31G*, 6-31+G*,`` and ``6-311G``.
3040 The total charge in `e` of the :mdp:`QMMM-grps`. In case there are
3041 more than one :mdp:`QMMM-grps`, the total charge of each ONIOM
3042 layer needs to be specified separately.
3047 The multiplicity of the :mdp:`QMMM-grps`. In case there are more
3048 than one :mdp:`QMMM-grps`, the multiplicity of each ONIOM layer
3049 needs to be specified separately.
3051 .. mdp:: CASorbitals
3054 The number of orbitals to be included in the active space when
3055 doing a CASSCF computation.
3057 .. mdp:: CASelectrons
3060 The number of electrons to be included in the active space when
3061 doing a CASSCF computation.
3067 No surface hopping. The system is always in the electronic
3072 Do a QM/MM MD simulation on the excited state-potential energy
3073 surface and enforce a *diabatic* hop to the ground-state when
3074 the system hits the conical intersection hyperline in the course
3075 the simulation. This option only works in combination with the
3079 Computational Electrophysiology
3080 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
3081 Use these options to switch on and control ion/water position exchanges in "Computational
3082 Electrophysiology" simulation setups. (See the `reference manual`_ for details).
3088 Do not enable ion/water position exchanges.
3090 .. mdp-value:: X ; Y ; Z
3092 Allow for ion/water position exchanges along the chosen direction.
3093 In a typical setup with the membranes parallel to the x-y plane,
3094 ion/water pairs need to be exchanged in Z direction to sustain the
3095 requested ion concentrations in the compartments.
3097 .. mdp:: swap-frequency
3099 (1) The swap attempt frequency, i.e. every how many time steps the ion counts
3100 per compartment are determined and exchanges made if necessary.
3101 Normally it is not necessary to check at every time step.
3102 For typical Computational Electrophysiology setups, a value of about 100 is
3103 sufficient and yields a negligible performance impact.
3105 .. mdp:: split-group0
3107 Name of the index group of the membrane-embedded part of channel #0.
3108 The center of mass of these atoms defines one of the compartment boundaries
3109 and should be chosen such that it is near the center of the membrane.
3111 .. mdp:: split-group1
3113 Channel #1 defines the position of the other compartment boundary.
3115 .. mdp:: massw-split0
3117 (no) Defines whether or not mass-weighting is used to calculate the split group center.
3121 Use the geometrical center.
3125 Use the center of mass.
3127 .. mdp:: massw-split1
3129 (no) As above, but for split-group #1.
3131 .. mdp:: solvent-group
3133 Name of the index group of solvent molecules.
3135 .. mdp:: coupl-steps
3137 (10) Average the number of ions per compartment over these many swap attempt steps.
3138 This can be used to prevent that ions near a compartment boundary
3139 (diffusing through a channel, e.g.) lead to unwanted back and forth swaps.
3143 (1) The number of different ion types to be controlled. These are during the
3144 simulation exchanged with solvent molecules to reach the desired reference numbers.
3146 .. mdp:: iontype0-name
3148 Name of the first ion type.
3150 .. mdp:: iontype0-in-A
3152 (-1) Requested (=reference) number of ions of type 0 in compartment A.
3153 The default value of -1 means: use the number of ions as found in time step 0
3156 .. mdp:: iontype0-in-B
3158 (-1) Reference number of ions of type 0 for compartment B.
3160 .. mdp:: bulk-offsetA
3162 (0.0) Offset of the first swap layer from the compartment A midplane.
3163 By default (i.e. bulk offset = 0.0), ion/water exchanges happen between layers
3164 at maximum distance (= bulk concentration) to the split group layers. However,
3165 an offset b (-1.0 < b < +1.0) can be specified to offset the bulk layer from the middle at 0.0
3166 towards one of the compartment-partitioning layers (at +/- 1.0).
3168 .. mdp:: bulk-offsetB
3170 (0.0) Offset of the other swap layer from the compartment B midplane.
3175 (\1) Only swap ions if threshold difference to requested count is reached.
3179 (2.0) [nm] Radius of the split cylinder #0.
3180 Two split cylinders (mimicking the channel pores) can optionally be defined
3181 relative to the center of the split group. With the help of these cylinders
3182 it can be counted which ions have passed which channel. The split cylinder
3183 definition has no impact on whether or not ion/water swaps are done.
3187 (1.0) [nm] Upper extension of the split cylinder #0.
3191 (1.0) [nm] Lower extension of the split cylinder #0.
3195 (2.0) [nm] Radius of the split cylinder #1.
3199 (1.0) [nm] Upper extension of the split cylinder #1.
3203 (1.0) [nm] Lower extension of the split cylinder #1.
3205 Density-guided simulations
3206 ^^^^^^^^^^^^^^^^^^^^^^^^^^
3208 These options enable and control the calculation and application of additional
3209 forces that are derived from three-dimensional densities, e.g., from cryo
3210 electron-microscopy experiments. (See the `reference manual`_ for details)
3212 .. mdp:: density-guided-simulation-active
3214 (no) Activate density-guided simulations.
3216 .. mdp:: density-guided-simulation-group
3218 (protein) The atoms that are subject to the forces from the density-guided
3219 simulation and contribute to the simulated density.
3221 .. mdp:: density-guided-simulation-similarity-measure
3223 (inner-product) Similarity measure between the density that is calculated
3224 from the atom positions and the reference density.
3226 .. mdp-value:: inner-product
3228 Takes the sum of the product of reference density and simulated density
3231 .. mdp-value:: relative-entropy
3233 Uses the negative relative entropy (or Kullback-Leibler divergence)
3234 between reference density and simulated density as similarity measure.
3235 Negative density values are ignored.
3237 .. mdp:: density-guided-simulation-atom-spreading-weight
3239 (unity) Determines the multiplication factor for the Gaussian kernel when
3240 spreading atoms on the grid.
3242 .. mdp-value:: unity
3244 Every atom in the density fitting group is assigned the same unit factor.
3248 Atoms contribute to the simulated density proportional to their mass.
3250 .. mdp-value:: charge
3252 Atoms contribute to the simulated density proportional to their charge.
3254 .. mdp:: density-guided-simulation-force-constant
3256 (1e+09) [kJ mol\ :sup:`-1`] The scaling factor for density-guided simulation
3257 forces. May also be negative.
3259 .. mdp:: density-guided-simulation-gaussian-transform-spreading-width
3261 (0.2) [nm] The Gaussian RMS width for the spread kernel for the simulated
3264 .. mdp:: density-guided-simulation-gaussian-transform-spreading-range-in-multiples-of-width
3266 (4) The range after which the gaussian is cut off in multiples of the Gaussian
3267 RMS width described above.
3269 .. mdp:: density-guided-simulation-reference-density-filename
3271 (reference.mrc) Reference density file name using an absolute path or a path
3272 relative to the to the folder from which :ref:`gmx mdrun` is called.
3274 .. mdp:: density-guided-simulation-nst
3276 (1) Interval in steps at which the density fitting forces are evaluated
3277 and applied. The forces are scaled by this number when applied (See the
3278 `reference manual`_ for details).
3280 .. mdp:: density-guided-simulation-normalize-densities
3282 (true) Normalize the sum of density voxel values to one for the reference
3283 density as well as the simulated density.
3285 .. mdp:: density-guided-simulation-adaptive-force-scaling
3287 (false) Adapt the force constant to ensure a steady increase in similarity
3288 between simulated and reference density.
3292 Do not use adaptive force scaling.
3296 Use adaptive force scaling.
3298 .. mdp:: density-guided-simulation-adaptive-force-scaling-time-constant
3300 (4) [ps] Couple force constant to increase in similarity with reference density
3301 with this time constant. Larger times result in looser coupling.
3303 User defined thingies
3304 ^^^^^^^^^^^^^^^^^^^^^
3308 .. mdp:: userint1 (0)
3309 .. mdp:: userint2 (0)
3310 .. mdp:: userint3 (0)
3311 .. mdp:: userint4 (0)
3312 .. mdp:: userreal1 (0)
3313 .. mdp:: userreal2 (0)
3314 .. mdp:: userreal3 (0)
3315 .. mdp:: userreal4 (0)
3317 These you can use if you modify code. You can pass integers and
3318 reals and groups to your subroutine. Check the inputrec definition
3319 in ``src/gromacs/mdtypes/inputrec.h``
3324 These features have been removed from |Gromacs|, but so that old
3325 :ref:`mdp` and :ref:`tpr` files cannot be mistakenly misused, we still
3326 parse this option. :ref:`gmx grompp` and :ref:`gmx mdrun` will issue a
3327 fatal error if this is set.
3333 .. mdp:: implicit-solvent
3337 .. _reference manual: gmx-manual-parent-dir_