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33 * GROningen Mixture of Alchemy and Childrens' Stories
45 #include "gmx_random.h"
47 #include "mtop_util.h"
49 static void low_mspeed(real tempi,
50 gmx_mtop_t *mtop, rvec v[], gmx_rng_t rng)
54 real ekin, temp, mass, scal;
55 gmx_mtop_atomloop_all_t aloop;
61 aloop = gmx_mtop_atomloop_all_init(mtop);
62 while (gmx_mtop_atomloop_all_next(aloop, &i, &atom))
67 sd = sqrt(boltz/mass);
68 for (m = 0; (m < DIM); m++)
70 v[i][m] = sd*gmx_rng_gaussian_real(rng);
71 ekin += 0.5*mass*v[i][m]*v[i][m];
76 temp = (2.0*ekin)/(nrdf*BOLTZ);
79 scal = sqrt(tempi/temp);
80 for (i = 0; (i < mtop->natoms); i++)
82 for (m = 0; (m < DIM); m++)
88 fprintf(stderr, "Velocities were taken from a Maxwell distribution at %g K\n",
93 "Velocities were taken from a Maxwell distribution\n"
94 "Initial generated temperature: %12.5e (scaled to: %12.5e)\n",
99 void maxwell_speed(real tempi, int seed, gmx_mtop_t *mtop, rvec v[])
108 fprintf(stderr, "Using random seed %d for generating velocities\n", seed);
111 rng = gmx_rng_init(seed);
113 low_mspeed(tempi, mtop, v, rng);
115 gmx_rng_destroy(rng);
118 real calc_cm(FILE *log, int natoms, real mass[], rvec x[], rvec v[],
119 rvec xcm, rvec vcm, rvec acm, matrix L)
129 for (i = 0; (i < natoms); i++)
133 cprod(x[i], v[i], a0);
134 for (m = 0; (m < DIM); m++)
136 xcm[m] += m0*x[i][m]; /* c.o.m. position */
137 vcm[m] += m0*v[i][m]; /* c.o.m. velocity */
138 acm[m] += m0*a0[m]; /* rotational velocity around c.o.m. */
142 for (m = 0; (m < DIM); m++)
149 #define PVEC(str, v) fprintf(log, \
150 "%s[X]: %10.5e %s[Y]: %10.5e %s[Z]: %10.5e\n", \
151 str, v[0], str, v[1], str, v[2])
159 for (i = 0; (i < natoms); i++)
162 for (m = 0; (m < DIM); m++)
164 dx[m] = x[i][m]-xcm[m];
166 L[XX][XX] += dx[XX]*dx[XX]*m0;
167 L[XX][YY] += dx[XX]*dx[YY]*m0;
168 L[XX][ZZ] += dx[XX]*dx[ZZ]*m0;
169 L[YY][YY] += dx[YY]*dx[YY]*m0;
170 L[YY][ZZ] += dx[YY]*dx[ZZ]*m0;
171 L[ZZ][ZZ] += dx[ZZ]*dx[ZZ]*m0;
182 void stop_cm(FILE *log, int natoms, real mass[], rvec x[], rvec v[])
189 fprintf(log, "stopping center of mass motion...\n");
191 (void)calc_cm(log, natoms, mass, x, v, xcm, vcm, acm, L);
193 /* Subtract center of mass velocity */
194 for (i = 0; (i < natoms); i++)
196 for (m = 0; (m < DIM); m++)
203 (void)calc_cm(log, natoms, mass, x, v, xcm, vcm, acm, L);