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ffa4ed00562002f700370f4dce697f355429f772
lammps/src/fix_restrain.cpp

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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing author: Craig Tenney (University of Notre Dame)
------------------------------------------------------------------------- */
#include "math.h"
#include "string.h"
#include "stdlib.h"
#include "fix_restrain.h"
#include "atom.h"
#include "force.h"
#include "update.h"
#include "domain.h"
#include "comm.h"
#include "respa.h"
#include "input.h"
#include "math_const.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
using namespace FixConst;
using namespace MathConst;
enum{DIHEDRAL};
#define TOLERANCE 0.05
/* ---------------------------------------------------------------------- */
FixRestrain::FixRestrain(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
int iarg = 6;
if (narg < iarg) error->all(FLERR,"Illegal fix restrain command");
scalar_flag = 1;
global_freq = 1;
extscalar = 1;
time_depend = 1;
// parse standard arguments
int n_atoms;
k_start = force->numeric(arg[3]);
k_stop = force->numeric(arg[4]);
if (strcmp(arg[5], "dihedral") == 0) {
rstyle = DIHEDRAL;
n_atoms = 4;
} else error->all(FLERR,"Illegal fix restrain command");
n_bonds = (narg - iarg) / (n_atoms + 1);
if (narg != iarg + n_bonds * (n_atoms + 1))
error->all(FLERR,"Illegal fix restrain command");
// allocate arrays
memory->create(atom_id,n_bonds,n_atoms,"restrain:atom_id");
memory->create(target,n_bonds,"restrain:taret");
// grab atom_ids and restraint target values
int ibond = 0;
while (iarg < narg) {
for (int i = 0; i < n_atoms; i++) {
atom_id[ibond][i] = force->inumeric(arg[iarg]);
iarg++;
}
target[ibond] = force->numeric(arg[iarg]);
iarg++;
ibond++;
}
// special treatment for dihedral restraints
if (rstyle == DIHEDRAL) {
cos_shift = (double *)
memory->smalloc(n_bonds * sizeof(double),"restrain:cos_shift");
sin_shift = (double *)
memory->smalloc(n_bonds * sizeof(double),"restrain:sin_shift");
for (ibond = 0; ibond < n_bonds; ibond++) {
double my_arg = MY_PI * (180.0 + target[ibond]) / 180.0;
cos_shift[ibond] = cos(my_arg);
sin_shift[ibond] = sin(my_arg);
}
}
// require atom map to lookup atom IDs
if (atom->map_style == 0)
error->all(FLERR,"Fix restrain requires an atom map, see atom_modify");
}
/* ---------------------------------------------------------------------- */
FixRestrain::~FixRestrain()
{
memory->destroy(atom_id);
memory->destroy(target);
if (rstyle == DIHEDRAL) {
memory->sfree(cos_shift);
memory->sfree(sin_shift);
}
}
/* ---------------------------------------------------------------------- */
int FixRestrain::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= THERMO_ENERGY;
mask |= POST_FORCE_RESPA;
mask |= MIN_POST_FORCE;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixRestrain::init()
{
if (strcmp(update->integrate_style,"respa") == 0)
nlevels_respa = ((Respa *) update->integrate)->nlevels;
}
/* ---------------------------------------------------------------------- */
void FixRestrain::setup(int vflag)
{
if (strcmp(update->integrate_style,"verlet") == 0)
post_force(vflag);
else {
((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
post_force_respa(vflag,nlevels_respa-1,0);
((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
}
}
/* ---------------------------------------------------------------------- */
void FixRestrain::min_setup(int vflag)
{
post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixRestrain::post_force(int vflag)
{
energy = 0.0;
if (rstyle == DIHEDRAL) restrain_dihedral();
}
/* ---------------------------------------------------------------------- */
void FixRestrain::post_force_respa(int vflag, int ilevel, int iloop)
{
if (ilevel == nlevels_respa-1) post_force(vflag);
}
/* ---------------------------------------------------------------------- */
void FixRestrain::min_post_force(int vflag)
{
post_force(vflag);
}
/* ----------------------------------------------------------------------
apply dihedral restraints
adopted from dihedral_charmm
---------------------------------------------------------------------- */
void FixRestrain::restrain_dihedral()
{
int i1,i2,i3,i4,i,m,n;
double vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z,vb2xm,vb2ym,vb2zm;
double f1[3],f2[3],f3[3],f4[3];
double ax,ay,az,bx,by,bz,rasq,rbsq,rgsq,rg,rginv,ra2inv,rb2inv,rabinv;
double df,df1,ddf1,fg,hg,fga,hgb,gaa,gbb;
double dtfx,dtfy,dtfz,dtgx,dtgy,dtgz,dthx,dthy,dthz;
double c,s,p,sx2,sy2,sz2;
double **x = atom->x;
double **f = atom->f;
int nlocal = atom->nlocal;
int newton_bond = force->newton_bond;
double delta = update->ntimestep - update->beginstep;
delta /= update->endstep - update->beginstep;
double k_step = k_start + delta * (k_stop - k_start);
for (n = 0; n < n_bonds; n++) {
i1 = atom->map(atom_id[n][0]);
i2 = atom->map(atom_id[n][1]);
i3 = atom->map(atom_id[n][2]);
i4 = atom->map(atom_id[n][3]);
// insure exactly one processor computes restraint
if (newton_bond) {
if (i2 == -1 || i2 >= nlocal) continue;
if (i1 == -1 || i3 == -1 || i4 == -1) {
char str[128];
sprintf(str,
"Restrain atoms %d %d %d %d missing on proc %d at step "
BIGINT_FORMAT,
atom_id[n][0],atom_id[n][1],atom_id[n][2],atom_id[n][3],
comm->me,update->ntimestep);
error->one(FLERR,str);
}
} else {
if ((i1 == -1 || i1 >= nlocal) && (i2 == -1 || i2 >= nlocal) &&
(i3 == -1 || i3 >= nlocal) && (i4 == -1 || i3 >= nlocal)) continue;
if (i1 == -1 || i2 == -1 || i3 == -1 || i4 == -1) {
char str[128];
sprintf(str,
"Restrain atoms %d %d %d %d missing on proc %d at step "
BIGINT_FORMAT,
atom_id[n][0],atom_id[n][1],atom_id[n][2],atom_id[n][3],
comm->me,update->ntimestep);
error->one(FLERR,str);
}
}
// 1st bond
vb1x = x[i1][0] - x[i2][0];
vb1y = x[i1][1] - x[i2][1];
vb1z = x[i1][2] - x[i2][2];
domain->minimum_image(vb1x,vb1y,vb1z);
// 2nd bond
vb2x = x[i3][0] - x[i2][0];
vb2y = x[i3][1] - x[i2][1];
vb2z = x[i3][2] - x[i2][2];
domain->minimum_image(vb2x,vb2y,vb2z);
vb2xm = -vb2x;
vb2ym = -vb2y;
vb2zm = -vb2z;
domain->minimum_image(vb2xm,vb2ym,vb2zm);
// 3rd bond
vb3x = x[i4][0] - x[i3][0];
vb3y = x[i4][1] - x[i3][1];
vb3z = x[i4][2] - x[i3][2];
domain->minimum_image(vb3x,vb3y,vb3z);
ax = vb1y*vb2zm - vb1z*vb2ym;
ay = vb1z*vb2xm - vb1x*vb2zm;
az = vb1x*vb2ym - vb1y*vb2xm;
bx = vb3y*vb2zm - vb3z*vb2ym;
by = vb3z*vb2xm - vb3x*vb2zm;
bz = vb3x*vb2ym - vb3y*vb2xm;
rasq = ax*ax + ay*ay + az*az;
rbsq = bx*bx + by*by + bz*bz;
rgsq = vb2xm*vb2xm + vb2ym*vb2ym + vb2zm*vb2zm;
rg = sqrt(rgsq);
rginv = ra2inv = rb2inv = 0.0;
if (rg > 0) rginv = 1.0/rg;
if (rasq > 0) ra2inv = 1.0/rasq;
if (rbsq > 0) rb2inv = 1.0/rbsq;
rabinv = sqrt(ra2inv*rb2inv);
c = (ax*bx + ay*by + az*bz)*rabinv;
s = rg*rabinv*(ax*vb3x + ay*vb3y + az*vb3z);
// error check
if (c > 1.0 + TOLERANCE || c < (-1.0 - TOLERANCE)) {
int me;
MPI_Comm_rank(world,&me);
if (screen) {
char str[128];
sprintf(str,"Restrain problem: %d " BIGINT_FORMAT " %d %d %d %d",
me,update->ntimestep,
atom->tag[i1],atom->tag[i2],atom->tag[i3],atom->tag[i4]);
error->warning(FLERR,str);
fprintf(screen," 1st atom: %d %g %g %g\n",
me,x[i1][0],x[i1][1],x[i1][2]);
fprintf(screen," 2nd atom: %d %g %g %g\n",
me,x[i2][0],x[i2][1],x[i2][2]);
fprintf(screen," 3rd atom: %d %g %g %g\n",
me,x[i3][0],x[i3][1],x[i3][2]);
fprintf(screen," 4th atom: %d %g %g %g\n",
me,x[i4][0],x[i4][1],x[i4][2]);
}
}
if (c > 1.0) c = 1.0;
if (c < -1.0) c = -1.0;
m = 1; //multiplicity
p = 1.0;
df1 = 0.0;
for (i = 0; i < m; i++) {
ddf1 = p*c - df1*s;
df1 = p*s + df1*c;
p = ddf1;
}
p = p*cos_shift[n] + df1*sin_shift[n];
df1 = df1*cos_shift[n] - ddf1*sin_shift[n];
df1 *= -m;
p += 1.0;
energy = k_step * p;
fg = vb1x*vb2xm + vb1y*vb2ym + vb1z*vb2zm;
hg = vb3x*vb2xm + vb3y*vb2ym + vb3z*vb2zm;
fga = fg*ra2inv*rginv;
hgb = hg*rb2inv*rginv;
gaa = -ra2inv*rg;
gbb = rb2inv*rg;
dtfx = gaa*ax;
dtfy = gaa*ay;
dtfz = gaa*az;
dtgx = fga*ax - hgb*bx;
dtgy = fga*ay - hgb*by;
dtgz = fga*az - hgb*bz;
dthx = gbb*bx;
dthy = gbb*by;
dthz = gbb*bz;
df = -k_step * df1;
sx2 = df*dtgx;
sy2 = df*dtgy;
sz2 = df*dtgz;
f1[0] = df*dtfx;
f1[1] = df*dtfy;
f1[2] = df*dtfz;
f2[0] = sx2 - f1[0];
f2[1] = sy2 - f1[1];
f2[2] = sz2 - f1[2];
f4[0] = df*dthx;
f4[1] = df*dthy;
f4[2] = df*dthz;
f3[0] = -sx2 - f4[0];
f3[1] = -sy2 - f4[1];
f3[2] = -sz2 - f4[2];
// apply force to each of 4 atoms
if (newton_bond || i1 < nlocal) {
f[i1][0] += f1[0];
f[i1][1] += f1[1];
f[i1][2] += f1[2];
}
if (newton_bond || i2 < nlocal) {
f[i2][0] += f2[0];
f[i2][1] += f2[1];
f[i2][2] += f2[2];
}
if (newton_bond || i3 < nlocal) {
f[i3][0] += f3[0];
f[i3][1] += f3[1];
f[i3][2] += f3[2];
}
if (newton_bond || i4 < nlocal) {
f[i4][0] += f4[0];
f[i4][1] += f4[1];
f[i4][2] += f4[2];
}
}
}
/* ----------------------------------------------------------------------
potential energy of added force
------------------------------------------------------------------------- */
double FixRestrain::compute_scalar()
{
MPI_Allreduce(&energy,&energy_all,1,MPI_DOUBLE,MPI_SUM,world);
return energy_all;
}
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