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40 #include "gen_maxwell_velocities.h"
44 #include "gromacs/math/units.h"
45 #include "gromacs/math/vec.h"
46 #include "gromacs/math/vectypes.h"
47 #include "gromacs/random/tabulatednormaldistribution.h"
48 #include "gromacs/random/threefry.h"
49 #include "gromacs/topology/mtop_util.h"
50 #include "gromacs/topology/topology.h"
51 #include "gromacs/utility/fatalerror.h"
52 #include "gromacs/utility/logger.h"
53 #include "gromacs/utility/smalloc.h"
55 static void low_mspeed(real tempi, gmx_mtop_t* mtop, rvec v[], gmx::ThreeFry2x64<>* rng, const gmx::MDLogger& logger)
59 gmx::TabulatedNormalDistribution<real> normalDist;
63 for (const AtomProxy atomP : AtomRange(*mtop))
65 const t_atom& local = atomP.atom();
66 int i = atomP.globalAtomNumber();
71 real sd = std::sqrt(gmx::c_boltz * tempi / mass);
72 for (int m = 0; (m < DIM); m++)
74 v[i][m] = sd * normalDist(*rng);
75 ekin += 0.5 * mass * v[i][m] * v[i][m];
80 temp = (2.0 * ekin) / (nrdf * gmx::c_boltz);
83 real scal = std::sqrt(tempi / temp);
84 for (int i = 0; (i < mtop->natoms); i++)
86 for (int m = 0; (m < DIM); m++)
94 .appendTextFormatted("Velocities were taken from a Maxwell distribution at %g K", tempi);
98 "Velocities were taken from a Maxwell distribution\n"
99 "Initial generated temperature: %12.5e (scaled to: %12.5e)\n",
105 void maxwell_speed(real tempi, unsigned int seed, gmx_mtop_t* mtop, rvec v[], const gmx::MDLogger& logger)
110 seed = static_cast<int>(gmx::makeRandomSeed());
113 .appendTextFormatted("Using random seed %u for generating velocities", seed);
115 gmx::ThreeFry2x64<> rng(seed, gmx::RandomDomain::MaxwellVelocities);
117 low_mspeed(tempi, mtop, v, &rng, logger);
120 static real calc_cm(int natoms, const real mass[], rvec x[], rvec v[], rvec xcm, rvec vcm, rvec acm, matrix L)
130 for (i = 0; (i < natoms); i++)
134 cprod(x[i], v[i], a0);
135 for (m = 0; (m < DIM); m++)
137 xcm[m] += m0 * x[i][m]; /* c.o.m. position */
138 vcm[m] += m0 * v[i][m]; /* c.o.m. velocity */
139 acm[m] += m0 * a0[m]; /* rotational velocity around c.o.m. */
143 for (m = 0; (m < DIM); m++)
147 acm[m] -= a0[m] / tm;
151 for (i = 0; (i < natoms); i++)
154 for (m = 0; (m < DIM); m++)
156 dx[m] = x[i][m] - xcm[m];
158 L[XX][XX] += dx[XX] * dx[XX] * m0;
159 L[XX][YY] += dx[XX] * dx[YY] * m0;
160 L[XX][ZZ] += dx[XX] * dx[ZZ] * m0;
161 L[YY][YY] += dx[YY] * dx[YY] * m0;
162 L[YY][ZZ] += dx[YY] * dx[ZZ] * m0;
163 L[ZZ][ZZ] += dx[ZZ] * dx[ZZ] * m0;
169 void stop_cm(const gmx::MDLogger gmx_unused& logger, int natoms, real mass[], rvec x[], rvec v[])
176 GMX_LOG(logger.info).asParagraph().appendTextFormatted("stopping center of mass motion...");
178 (void)calc_cm(natoms, mass, x, v, xcm, vcm, acm, L);
180 /* Subtract center of mass velocity */
181 for (i = 0; (i < natoms); i++)
183 for (m = 0; (m < DIM); m++)