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44 #include "gromacs/commandline/pargs.h"
45 #include "gromacs/commandline/viewit.h"
46 #include "gromacs/fileio/trxio.h"
47 #include "gromacs/fileio/xvgr.h"
48 #include "gromacs/gmxana/gmx_ana.h"
49 #include "gromacs/gmxana/princ.h"
50 #include "gromacs/math/functions.h"
51 #include "gromacs/math/units.h"
52 #include "gromacs/math/utilities.h"
53 #include "gromacs/math/vec.h"
54 #include "gromacs/pbcutil/rmpbc.h"
55 #include "gromacs/topology/index.h"
56 #include "gromacs/topology/topology.h"
57 #include "gromacs/utility/arraysize.h"
58 #include "gromacs/utility/cstringutil.h"
59 #include "gromacs/utility/fatalerror.h"
60 #include "gromacs/utility/futil.h"
61 #include "gromacs/utility/smalloc.h"
63 #define EPS0 8.85419E-12
64 #define ELC 1.60219E-19
66 /****************************************************************************/
67 /* This program calculates the electrostatic potential across the box by */
68 /* determining the charge density in slices of the box and integrating these*/
70 /* Peter Tieleman, April 1995 */
71 /* It now also calculates electrostatic potential in spherical micelles, */
72 /* using \frac{1}{r}\frac{d^2r\Psi}{r^2} = - \frac{\rho}{\epsilon_0} */
73 /* This probably sucks but it seems to work. */
74 /****************************************************************************/
76 /* this routine integrates the array data and returns the resulting array */
77 /* routine uses simple trapezoid rule */
78 static void p_integrate(double* result, const double data[], int ndata, double slWidth, int cb, int ce)
86 "Warning: nr of slices very small. This will result"
90 fprintf(stderr, "Integrating from slice %d to slice %d\n", cb, ndata - ce);
92 for (slice = cb; slice < (ndata - ce); slice++)
95 for (i = cb; i < slice; i++)
97 sum += slWidth * (data[i] + 0.5 * (data[i + 1] - data[i]));
103 static void calc_potential(const char* fn,
106 double*** slPotential,
110 const t_topology* top,
120 const gmx_output_env_t* oenv)
122 rvec* x0; /* coordinates without pbc */
123 matrix box; /* box (3x3) */
124 int natoms; /* nr. atoms in trj */
126 int i, n, /* loop indices */
127 teller = 0, ax1 = 0, ax2 = 0, nr_frames = 0, /* number of frames */
128 slice; /* current slice */
129 double slVolume; /* volume of slice for spherical averaging */
134 gmx_rmpbc_t gpbc = nullptr;
150 default: gmx_fatal(FARGS, "Invalid axes. Terminating\n");
153 if ((natoms = read_first_x(oenv, &status, fn, &t, &x0, box)) == 0)
155 gmx_fatal(FARGS, "Could not read coordinates from statusfile\n");
160 *nslices = static_cast<int>(box[axis][axis] * 10.0); /* default value */
162 fprintf(stderr, "\nDividing the box in %d slices\n", *nslices);
164 snew(*slField, nr_grps);
165 snew(*slCharge, nr_grps);
166 snew(*slPotential, nr_grps);
168 for (i = 0; i < nr_grps; i++)
170 snew((*slField)[i], *nslices);
171 snew((*slCharge)[i], *nslices);
172 snew((*slPotential)[i], *nslices);
176 gpbc = gmx_rmpbc_init(&top->idef, pbcType, natoms);
178 /*********** Start processing trajectory ***********/
181 *slWidth = box[axis][axis] / static_cast<real>((*nslices));
183 gmx_rmpbc(gpbc, natoms, box, x0);
185 /* calculate position of center of mass based on group 1 */
186 calc_xcm(x0, gnx[0], index[0], top->atoms.atom, xcm, FALSE);
189 for (n = 0; n < nr_grps; n++)
191 /* Check whether we actually have all positions of the requested index
192 * group in the trajectory file */
196 "You selected a group with %d atoms, but only %d atoms\n"
197 "were found in the trajectory.\n",
201 for (i = 0; i < gnx[n]; i++) /* loop over all atoms in index file */
205 rvec_add(x0[index[n][i]], xcm, x0[index[n][i]]);
206 /* only distance from origin counts, not sign */
207 slice = static_cast<int>(norm(x0[index[n][i]]) / (*slWidth));
209 /* this is a nice check for spherical groups but not for
210 all water in a cubic box since a lot will fall outside
212 if (slice > (*nslices))
214 fprintf(stderr,"Warning: slice = %d\n",slice);
217 (*slCharge)[n][slice] += top->atoms.atom[index[n][i]].q;
221 z = x0[index[n][i]][axis];
225 z += box[axis][axis];
227 if (z > box[axis][axis])
229 z -= box[axis][axis];
231 /* determine which slice atom is in */
232 slice = static_cast<int>((z / (*slWidth)));
233 (*slCharge)[n][slice] += top->atoms.atom[index[n][i]].q;
238 } while (read_next_x(oenv, status, &t, x0, box));
240 gmx_rmpbc_done(gpbc);
242 /*********** done with status file **********/
245 /* slCharge now contains the total charge per slice, summed over all
246 frames. Now divide by nr_frames and integrate twice
253 "\n\nRead %d frames from trajectory. Calculating potential"
254 "in spherical coordinates\n",
259 fprintf(stderr, "\n\nRead %d frames from trajectory. Calculating potential\n", nr_frames);
262 for (n = 0; n < nr_grps; n++)
264 for (i = 0; i < *nslices; i++)
268 /* charge per volume is now the summed charge, divided by the nr
269 of frames and by the volume of the slice it's in, 4pi r^2 dr
271 slVolume = 4 * M_PI * gmx::square(i) * gmx::square(*slWidth) * *slWidth;
274 (*slCharge)[n][i] = 0;
278 (*slCharge)[n][i] = (*slCharge)[n][i] / (nr_frames * slVolume);
283 /* get charge per volume */
284 (*slCharge)[n][i] = (*slCharge)[n][i] * (*nslices)
285 / (static_cast<real>(nr_frames) * box[axis][axis]
286 * box[ax1][ax1] * box[ax2][ax2]);
289 /* Now we have charge densities */
292 if (bCorrect && !bSpherical)
294 for (n = 0; n < nr_grps; n++)
298 for (i = 0; i < *nslices; i++)
300 if (std::abs((*slCharge)[n][i]) >= GMX_DOUBLE_MIN)
303 qsum += (*slCharge)[n][i];
307 for (i = 0; i < *nslices; i++)
309 if (std::abs((*slCharge)[n][i]) >= GMX_DOUBLE_MIN)
311 (*slCharge)[n][i] -= qsum;
317 for (n = 0; n < nr_grps; n++)
319 /* integrate twice to get field and potential */
320 p_integrate((*slField)[n], (*slCharge)[n], *nslices, *slWidth, cb, ce);
324 if (bCorrect && !bSpherical)
326 for (n = 0; n < nr_grps; n++)
330 for (i = 0; i < *nslices; i++)
332 if (std::abs((*slCharge)[n][i]) >= GMX_DOUBLE_MIN)
335 qsum += (*slField)[n][i];
339 for (i = 0; i < *nslices; i++)
341 if (std::abs((*slCharge)[n][i]) >= GMX_DOUBLE_MIN)
343 (*slField)[n][i] -= qsum;
349 for (n = 0; n < nr_grps; n++)
351 p_integrate((*slPotential)[n], (*slField)[n], *nslices, *slWidth, cb, ce);
354 /* Now correct for eps0 and in spherical case for r*/
355 for (n = 0; n < nr_grps; n++)
357 for (i = 0; i < *nslices; i++)
361 (*slPotential)[n][i] = ELC * (*slPotential)[n][i] * -1.0E9 / (EPS0 * i * (*slWidth));
362 (*slField)[n][i] = ELC * (*slField)[n][i] * 1E18 / (EPS0 * i * (*slWidth));
366 (*slPotential)[n][i] = ELC * (*slPotential)[n][i] * -1.0E9 / EPS0;
367 (*slField)[n][i] = ELC * (*slField)[n][i] * 1E18 / EPS0;
372 sfree(x0); /* free memory used by coordinate array */
375 static void plot_potential(double* potential[],
383 const char* const grpname[],
387 const gmx_output_env_t* oenv)
389 FILE *pot, /* xvgr file with potential */
390 *cha, /* xvgr file with charges */
391 *fie; /* xvgr files with fields */
392 char buf[256]; /* for xvgr title */
395 sprintf(buf, "Electrostatic Potential");
396 pot = xvgropen(afile, buf, "Box (nm)", "Potential (V)", oenv);
397 xvgr_legend(pot, nr_grps, grpname, oenv);
399 sprintf(buf, "Charge Distribution");
400 cha = xvgropen(bfile, buf, "Box (nm)", "Charge density (q/nm\\S3\\N)", oenv);
401 xvgr_legend(cha, nr_grps, grpname, oenv);
403 sprintf(buf, "Electric Field");
404 fie = xvgropen(cfile, buf, "Box (nm)", "Field (V/nm)", oenv);
405 xvgr_legend(fie, nr_grps, grpname, oenv);
407 for (slice = cb; slice < (nslices - ce); slice++)
409 fprintf(pot, "%20.16g ", slice * slWidth);
410 fprintf(cha, "%20.16g ", slice * slWidth);
411 fprintf(fie, "%20.16g ", slice * slWidth);
412 for (n = 0; n < nr_grps; n++)
414 fprintf(pot, " %20.16g", potential[n][slice]);
415 fprintf(fie, " %20.16g", field[n][slice] / 1e9); /* convert to V/nm */
416 fprintf(cha, " %20.16g", charge[n][slice]);
428 int gmx_potential(int argc, char* argv[])
430 const char* desc[] = {
431 "[THISMODULE] computes the electrostatical potential across the box. The potential is",
432 "calculated by first summing the charges per slice and then integrating",
433 "twice of this charge distribution. Periodic boundaries are not taken",
434 "into account. Reference of potential is taken to be the left side of",
435 "the box. It is also possible to calculate the potential in spherical",
436 "coordinates as function of r by calculating a charge distribution in",
437 "spherical slices and twice integrating them. epsilon_r is taken as 1,",
438 "but 2 is more appropriate in many cases."
440 gmx_output_env_t* oenv;
441 static int axis = 2; /* normal to memb. default z */
442 static const char* axtitle = "Z";
443 static int nslices = 10; /* nr of slices defined */
444 static int ngrps = 1;
445 static gmx_bool bSpherical = FALSE; /* default is bilayer types */
446 static real fudge_z = 0; /* translate coordinates */
447 static gmx_bool bCorrect = false;
455 "Take the normal on the membrane in direction X, Y or Z." },
460 "Calculate potential as function of boxlength, dividing the box"
461 " in this number of slices." },
466 "Discard this number of first slices of box for integration" },
471 "Discard this number of last slices of box for integration" },
476 "Translate all coordinates by this distance in the direction of the box" },
477 { "-spherical", FALSE, etBOOL, { &bSpherical }, "Calculate in spherical coordinates" },
478 { "-ng", FALSE, etINT, { &ngrps }, "Number of groups to consider" },
483 "Assume net zero charge of groups to improve accuracy" }
485 const char* bugs[] = { "Discarding slices for integration should not be necessary." };
487 double **potential, /* potential per slice */
488 **charge, /* total charge per slice */
489 **field, /* field per slice */
490 slWidth; /* width of one slice */
491 char** grpname; /* groupnames */
492 int* ngx; /* sizes of groups */
493 t_topology* top; /* topology */
495 int** index; /* indices for all groups */
497 /* files for g_order */
498 { efTRX, "-f", nullptr, ffREAD }, /* trajectory file */
499 { efNDX, nullptr, nullptr, ffREAD }, /* index file */
500 { efTPR, nullptr, nullptr, ffREAD }, /* topology file */
501 { efXVG, "-o", "potential", ffWRITE }, /* xvgr output file */
502 { efXVG, "-oc", "charge", ffWRITE }, /* xvgr output file */
503 { efXVG, "-of", "field", ffWRITE }, /* xvgr output file */
506 #define NFILE asize(fnm)
508 if (!parse_common_args(
509 &argc, argv, PCA_CAN_VIEW | PCA_CAN_TIME, NFILE, fnm, asize(pa), pa, asize(desc), desc, asize(bugs), bugs, &oenv))
515 axis = toupper(axtitle[0]) - 'X';
517 top = read_top(ftp2fn(efTPR, NFILE, fnm), &pbcType); /* read topology file */
519 snew(grpname, ngrps);
523 rd_index(ftp2fn(efNDX, NFILE, fnm), ngrps, ngx, index, grpname);
526 calc_potential(ftp2fn(efTRX, NFILE, fnm),
545 plot_potential(potential,
548 opt2fn("-o", NFILE, fnm),
549 opt2fn("-oc", NFILE, fnm),
550 opt2fn("-of", NFILE, fnm),
559 do_view(oenv, opt2fn("-o", NFILE, fnm), nullptr); /* view xvgr file */
560 do_view(oenv, opt2fn("-oc", NFILE, fnm), nullptr); /* view xvgr file */
561 do_view(oenv, opt2fn("-of", NFILE, fnm), nullptr); /* view xvgr file */