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dihedral_charmm.cpp
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Sat, Nov 16, 21:20

dihedral_charmm.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: Paul Crozier (SNL)
------------------------------------------------------------------------- */
#include "lmptype.h"
#include "mpi.h"
#include "math.h"
#include "stdlib.h"
#include "dihedral_charmm.h"
#include "atom.h"
#include "comm.h"
#include "neighbor.h"
#include "domain.h"
#include "force.h"
#include "pair.h"
#include "update.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
#define TOLERANCE 0.05
/* ---------------------------------------------------------------------- */
DihedralCharmm::DihedralCharmm(LAMMPS *lmp) : Dihedral(lmp) {}
/* ---------------------------------------------------------------------- */
DihedralCharmm::~DihedralCharmm()
{
if (allocated) {
memory->destroy(setflag);
memory->destroy(k);
memory->destroy(multiplicity);
memory->destroy(shift);
memory->destroy(cos_shift);
memory->destroy(sin_shift);
memory->destroy(weight);
}
}
/* ---------------------------------------------------------------------- */
void DihedralCharmm::compute(int eflag, int vflag)
{
int i1,i2,i3,i4,i,m,n,type;
double vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z,vb2xm,vb2ym,vb2zm;
double edihedral,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;
int itype,jtype;
double delx,dely,delz,rsq,r2inv,r6inv;
double forcecoul,forcelj,fpair,ecoul,evdwl;
edihedral = evdwl = ecoul = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = 0;
// insure pair->ev_tally() will use 1-4 virial contribution
if (weightflag && vflag_global == 2)
force->pair->vflag_either = force->pair->vflag_global = 1;
double **x = atom->x;
double **f = atom->f;
double *q = atom->q;
int *atomtype = atom->type;
int **dihedrallist = neighbor->dihedrallist;
int ndihedrallist = neighbor->ndihedrallist;
int nlocal = atom->nlocal;
int newton_bond = force->newton_bond;
double qqrd2e = force->qqrd2e;
for (n = 0; n < ndihedrallist; n++) {
i1 = dihedrallist[n][0];
i2 = dihedrallist[n][1];
i3 = dihedrallist[n][2];
i4 = dihedrallist[n][3];
type = dihedrallist[n][4];
// 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,"Dihedral 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(str,0);
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 = multiplicity[type];
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[type] + df1*sin_shift[type];
df1 = df1*cos_shift[type] - ddf1*sin_shift[type];
df1 *= -m;
p += 1.0;
if (m == 0) {
p = 1.0 + cos_shift[type];
df1 = 0.0;
}
if (eflag) edihedral = k[type] * 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[type] * 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];
}
if (evflag)
ev_tally(i1,i2,i3,i4,nlocal,newton_bond,edihedral,f1,f3,f4,
vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z);
// 1-4 LJ and Coulomb interactions
// tally energy/virial in pair, using newton_bond as newton flag
if (weight[type] > 0.0) {
itype = atomtype[i1];
jtype = atomtype[i4];
delx = x[i1][0] - x[i4][0];
dely = x[i1][1] - x[i4][1];
delz = x[i1][2] - x[i4][2];
domain->minimum_image(delx,dely,delz);
rsq = delx*delx + dely*dely + delz*delz;
r2inv = 1.0/rsq;
r6inv = r2inv*r2inv*r2inv;
if (implicit) forcecoul = qqrd2e * q[i1]*q[i4]*r2inv;
else forcecoul = qqrd2e * q[i1]*q[i4]*sqrt(r2inv);
forcelj = r6inv * (lj14_1[itype][jtype]*r6inv - lj14_2[itype][jtype]);
fpair = weight[type] * (forcelj+forcecoul)*r2inv;
if (eflag) {
ecoul = weight[type] * forcecoul;
evdwl = r6inv * (lj14_3[itype][jtype]*r6inv - lj14_4[itype][jtype]);
evdwl *= weight[type];
}
if (newton_bond || i1 < nlocal) {
f[i1][0] += delx*fpair;
f[i1][1] += dely*fpair;
f[i1][2] += delz*fpair;
}
if (newton_bond || i4 < nlocal) {
f[i4][0] -= delx*fpair;
f[i4][1] -= dely*fpair;
f[i4][2] -= delz*fpair;
}
if (evflag) force->pair->ev_tally(i1,i4,nlocal,newton_bond,
evdwl,ecoul,fpair,delx,dely,delz);
}
}
}
/* ---------------------------------------------------------------------- */
void DihedralCharmm::allocate()
{
allocated = 1;
int n = atom->ndihedraltypes;
memory->create(k,n+1,"dihedral:k");
memory->create(multiplicity,n+1,"dihedral:k");
memory->create(shift,n+1,"dihedral:shift");
memory->create(cos_shift,n+1,"dihedral:cos_shift");
memory->create(sin_shift,n+1,"dihedral:sin_shift");
memory->create(weight,n+1,"dihedral:weight");
memory->create(setflag,n+1,"dihedral:setflag");
for (int i = 1; i <= n; i++) setflag[i] = 0;
}
/* ----------------------------------------------------------------------
set coeffs for one type
------------------------------------------------------------------------- */
void DihedralCharmm::coeff(int narg, char **arg)
{
if (narg != 5) error->all("Incorrect args for dihedral coefficients");
if (!allocated) allocate();
int ilo,ihi;
force->bounds(arg[0],atom->ndihedraltypes,ilo,ihi);
// require integer values of shift for backwards compatibility
// arbitrary phase angle shift could be allowed, but would break
// backwards compatibility and is probably not needed
double k_one = force->numeric(arg[1]);
int multiplicity_one = force->inumeric(arg[2]);
int shift_one = force->inumeric(arg[3]);
double weight_one = force->numeric(arg[4]);
if (multiplicity_one < 0)
error->all("Incorrect multiplicity arg for dihedral coefficients");
if (weight_one < 0.0 || weight_one > 1.0)
error->all("Incorrect weight arg for dihedral coefficients");
double PI = 4.0*atan(1.0);
int count = 0;
for (int i = ilo; i <= ihi; i++) {
k[i] = k_one;
shift[i] = shift_one;
cos_shift[i] = cos(PI*shift_one/180.0);
sin_shift[i] = sin(PI*shift_one/180.0);
multiplicity[i] = multiplicity_one;
weight[i] = weight_one;
setflag[i] = 1;
count++;
}
if (count == 0) error->all("Incorrect args for dihedral coefficients");
}
/* ----------------------------------------------------------------------
error check and initialize all values needed for force computation
------------------------------------------------------------------------- */
void DihedralCharmm::init_style()
{
// insure use of CHARMM pair_style if any weight factors are non-zero
// set local ptrs to LJ 14 arrays setup by Pair
weightflag = 0;
for (int i = 1; i <= atom->ndihedraltypes; i++)
if (weight[i] > 0.0) weightflag = 1;
if (weightflag) {
int itmp;
if (force->pair == NULL)
error->all("Dihedral charmm is incompatible with Pair style");
lj14_1 = (double **) force->pair->extract("lj14_1",itmp);
lj14_2 = (double **) force->pair->extract("lj14_2",itmp);
lj14_3 = (double **) force->pair->extract("lj14_3",itmp);
lj14_4 = (double **) force->pair->extract("lj14_4",itmp);
int *ptr = (int *) force->pair->extract("implicit",itmp);
if (!lj14_1 || !lj14_2 || !lj14_3 || !lj14_4 || !ptr)
error->all("Dihedral charmm is incompatible with Pair style");
implicit = *ptr;
}
}
/* ----------------------------------------------------------------------
proc 0 writes out coeffs to restart file
------------------------------------------------------------------------- */
void DihedralCharmm::write_restart(FILE *fp)
{
fwrite(&k[1],sizeof(double),atom->ndihedraltypes,fp);
fwrite(&multiplicity[1],sizeof(int),atom->ndihedraltypes,fp);
fwrite(&shift[1],sizeof(int),atom->ndihedraltypes,fp);
fwrite(&weight[1],sizeof(double),atom->ndihedraltypes,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads coeffs from restart file, bcasts them
------------------------------------------------------------------------- */
void DihedralCharmm::read_restart(FILE *fp)
{
allocate();
if (comm->me == 0) {
fread(&k[1],sizeof(double),atom->ndihedraltypes,fp);
fread(&multiplicity[1],sizeof(int),atom->ndihedraltypes,fp);
fread(&shift[1],sizeof(int),atom->ndihedraltypes,fp);
fread(&weight[1],sizeof(double),atom->ndihedraltypes,fp);
}
MPI_Bcast(&k[1],atom->ndihedraltypes,MPI_DOUBLE,0,world);
MPI_Bcast(&multiplicity[1],atom->ndihedraltypes,MPI_INT,0,world);
MPI_Bcast(&shift[1],atom->ndihedraltypes,MPI_INT,0,world);
MPI_Bcast(&weight[1],atom->ndihedraltypes,MPI_DOUBLE,0,world);
double PI = 4.0*atan(1.0);
for (int i = 1; i <= atom->ndihedraltypes; i++) {
setflag[i] = 1;
cos_shift[i] = cos(PI*shift[i]/180.0);
sin_shift[i] = sin(PI*shift[i]/180.0);
}
}

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