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angle_sdk.cpp
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angle_sdk.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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Variant of the harmonic angle potential for use with the
lj/sdk potential for coarse grained MD simulations.
Contributing author: Axel Kohlmeyer (Temple U)
------------------------------------------------------------------------- */
#include <math.h>
#include <stdlib.h>
#include "angle_sdk.h"
#include "atom.h"
#include "neighbor.h"
#include "pair.h"
#include "domain.h"
#include "comm.h"
#include "force.h"
#include "math_const.h"
#include "memory.h"
#include "error.h"
#include "lj_sdk_common.h"
using namespace LAMMPS_NS;
using namespace MathConst;
using namespace LJSDKParms;
#define SMALL 0.001
/* ---------------------------------------------------------------------- */
AngleSDK::AngleSDK(LAMMPS *lmp) : Angle(lmp) { repflag = 0;}
/* ---------------------------------------------------------------------- */
AngleSDK::~AngleSDK()
{
if (allocated) {
memory->destroy(setflag);
memory->destroy(k);
memory->destroy(theta0);
memory->destroy(repscale);
allocated = 0;
}
}
/* ---------------------------------------------------------------------- */
void AngleSDK::compute(int eflag, int vflag)
{
int i1,i2,i3,n,type;
double delx1,dely1,delz1,delx2,dely2,delz2,delx3,dely3,delz3;
double eangle,f1[3],f3[3],e13,f13;
double dtheta,tk;
double rsq1,rsq2,rsq3,r1,r2,c,s,a,a11,a12,a22;
eangle = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = 0;
double **x = atom->x;
double **f = atom->f;
int **anglelist = neighbor->anglelist;
int nanglelist = neighbor->nanglelist;
int nlocal = atom->nlocal;
int newton_bond = force->newton_bond;
for (n = 0; n < nanglelist; n++) {
i1 = anglelist[n][0];
i2 = anglelist[n][1];
i3 = anglelist[n][2];
type = anglelist[n][3];
// 1st bond
delx1 = x[i1][0] - x[i2][0];
dely1 = x[i1][1] - x[i2][1];
delz1 = x[i1][2] - x[i2][2];
rsq1 = delx1*delx1 + dely1*dely1 + delz1*delz1;
r1 = sqrt(rsq1);
// 2nd bond
delx2 = x[i3][0] - x[i2][0];
dely2 = x[i3][1] - x[i2][1];
delz2 = x[i3][2] - x[i2][2];
rsq2 = delx2*delx2 + dely2*dely2 + delz2*delz2;
r2 = sqrt(rsq2);
// angle (cos and sin)
c = delx1*delx2 + dely1*dely2 + delz1*delz2;
c /= r1*r2;
if (c > 1.0) c = 1.0;
if (c < -1.0) c = -1.0;
s = sqrt(1.0 - c*c);
if (s < SMALL) s = SMALL;
s = 1.0/s;
// 1-3 LJ interaction.
// we only want to use the repulsive part,
// and it can be scaled (or off).
// so this has to be done here and not in the
// general non-bonded code.
f13 = e13 = delx3 = dely3 = delz3 = 0.0;
if (repflag) {
delx3 = x[i1][0] - x[i3][0];
dely3 = x[i1][1] - x[i3][1];
delz3 = x[i1][2] - x[i3][2];
rsq3 = delx3*delx3 + dely3*dely3 + delz3*delz3;
const int type1 = atom->type[i1];
const int type3 = atom->type[i3];
f13=0.0;
e13=0.0;
if (rsq3 < rminsq[type1][type3]) {
const int ljt = lj_type[type1][type3];
const double r2inv = 1.0/rsq3;
if (ljt == LJ12_4) {
const double r4inv=r2inv*r2inv;
f13 = r4inv*(lj1[type1][type3]*r4inv*r4inv - lj2[type1][type3]);
if (eflag) e13 = r4inv*(lj3[type1][type3]*r4inv*r4inv - lj4[type1][type3]);
} else if (ljt == LJ9_6) {
const double r3inv = r2inv*sqrt(r2inv);
const double r6inv = r3inv*r3inv;
f13 = r6inv*(lj1[type1][type3]*r3inv - lj2[type1][type3]);
if (eflag) e13 = r6inv*(lj3[type1][type3]*r3inv - lj4[type1][type3]);
} else if (ljt == LJ12_6) {
const double r6inv = r2inv*r2inv*r2inv;
f13 = r6inv*(lj1[type1][type3]*r6inv - lj2[type1][type3]);
if (eflag) e13 = r6inv*(lj3[type1][type3]*r6inv - lj4[type1][type3]);
}
// make sure energy is 0.0 at the cutoff.
if (eflag) e13 -= emin[type1][type3];
f13 *= r2inv;
}
}
// force & energy
dtheta = acos(c) - theta0[type];
tk = k[type] * dtheta;
if (eflag) eangle = tk*dtheta;
a = -2.0 * tk * s;
a11 = a*c / rsq1;
a12 = -a / (r1*r2);
a22 = a*c / rsq2;
f1[0] = a11*delx1 + a12*delx2;
f1[1] = a11*dely1 + a12*dely2;
f1[2] = a11*delz1 + a12*delz2;
f3[0] = a22*delx2 + a12*delx1;
f3[1] = a22*dely2 + a12*dely1;
f3[2] = a22*delz2 + a12*delz1;
// apply force to each of the 3 atoms
if (newton_bond || i1 < nlocal) {
f[i1][0] += f1[0] + f13*delx3;
f[i1][1] += f1[1] + f13*dely3;
f[i1][2] += f1[2] + f13*delz3;
}
if (newton_bond || i2 < nlocal) {
f[i2][0] -= f1[0] + f3[0];
f[i2][1] -= f1[1] + f3[1];
f[i2][2] -= f1[2] + f3[2];
}
if (newton_bond || i3 < nlocal) {
f[i3][0] += f3[0] - f13*delx3;
f[i3][1] += f3[1] - f13*dely3;
f[i3][2] += f3[2] - f13*delz3;
}
if (evflag) {
ev_tally(i1,i2,i3,nlocal,newton_bond,eangle,f1,f3,
delx1,dely1,delz1,delx2,dely2,delz2);
if (repflag)
ev_tally13(i1,i3,nlocal,newton_bond,e13,f13,delx3,dely3,delz3);
}
}
}
/* ---------------------------------------------------------------------- */
void AngleSDK::allocate()
{
allocated = 1;
int n = atom->nangletypes;
memory->create(k,n+1,"angle:k");
memory->create(theta0,n+1,"angle:theta0");
memory->create(repscale,n+1,"angle:repscale");
memory->create(setflag,n+1,"angle:setflag");
for (int i = 1; i <= n; i++) setflag[i] = 0;
}
/* ----------------------------------------------------------------------
set coeffs for one or more types
------------------------------------------------------------------------- */
void AngleSDK::coeff(int narg, char **arg)
{
if ((narg < 3) || (narg > 6))
error->all(FLERR,"Incorrect args for angle coefficients");
if (!allocated) allocate();
int ilo,ihi;
force->bounds(arg[0],atom->nangletypes,ilo,ihi);
double k_one = force->numeric(FLERR,arg[1]);
double theta0_one = force->numeric(FLERR,arg[2]);
double repscale_one=1.0;
// backward compatibility with old cg/cmm style input:
// this had <lj_type> <epsilon> <sigma>
// if epsilon is set to 0.0 we accept it as repscale 0.0
// otherwise assume repscale 1.0, since we were using
// epsilon to turn repulsion on or off.
if (narg == 6) {
repscale_one = force->numeric(FLERR,arg[4]);
if (repscale_one > 0.0) repscale_one = 1.0;
} else if (narg == 4) repscale_one = force->numeric(FLERR,arg[3]);
else if (narg == 3) repscale_one = 1.0;
else error->all(FLERR,"Incorrect args for angle coefficients");
// convert theta0 from degrees to radians and store coefficients
int count = 0;
for (int i = ilo; i <= ihi; i++) {
k[i] = k_one;
theta0[i] = theta0_one/180.0 * MY_PI;
repscale[i] = repscale_one;
setflag[i] = 1;
count++;
}
if (count == 0) error->all(FLERR,"Incorrect args for angle coefficients");
}
/* ----------------------------------------------------------------------
error check and initialize all values needed for force computation
------------------------------------------------------------------------- */
void AngleSDK::init_style()
{
// make sure we use an SDK pair_style and that we need the 1-3 repulsion
repflag = 0;
for (int i = 1; i <= atom->nangletypes; i++)
if (repscale[i] > 0.0) repflag = 1;
// set up pointers to access SDK LJ parameters for 1-3 interactions
if (repflag) {
int itmp;
if (force->pair == NULL)
error->all(FLERR,"Angle style SDK requires use of a compatible with Pair style");
lj1 = (double **) force->pair->extract("lj1",itmp);
lj2 = (double **) force->pair->extract("lj2",itmp);
lj3 = (double **) force->pair->extract("lj3",itmp);
lj4 = (double **) force->pair->extract("lj4",itmp);
lj_type = (int **) force->pair->extract("lj_type",itmp);
rminsq = (double **) force->pair->extract("rminsq",itmp);
emin = (double **) force->pair->extract("emin",itmp);
if (!lj1 || !lj2 || !lj3 || !lj4 || !lj_type || !rminsq || !emin)
error->all(FLERR,"Angle style SDK is incompatible with Pair style");
}
}
/* ---------------------------------------------------------------------- */
double AngleSDK::equilibrium_angle(int i)
{
return theta0[i];
}
/* ----------------------------------------------------------------------
proc 0 writes out coeffs to restart file
------------------------------------------------------------------------- */
void AngleSDK::write_restart(FILE *fp)
{
fwrite(&k[1],sizeof(double),atom->nangletypes,fp);
fwrite(&theta0[1],sizeof(double),atom->nangletypes,fp);
fwrite(&repscale[1],sizeof(double),atom->nangletypes,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads coeffs from restart file, bcasts them
------------------------------------------------------------------------- */
void AngleSDK::read_restart(FILE *fp)
{
allocate();
if (comm->me == 0) {
fread(&k[1],sizeof(double),atom->nangletypes,fp);
fread(&theta0[1],sizeof(double),atom->nangletypes,fp);
fread(&repscale[1],sizeof(double),atom->nangletypes,fp);
}
MPI_Bcast(&k[1],atom->nangletypes,MPI_DOUBLE,0,world);
MPI_Bcast(&theta0[1],atom->nangletypes,MPI_DOUBLE,0,world);
MPI_Bcast(&repscale[1],atom->nangletypes,MPI_DOUBLE,0,world);
for (int i = 1; i <= atom->nangletypes; i++) setflag[i] = 1;
}
/* ----------------------------------------------------------------------
proc 0 writes to data file
------------------------------------------------------------------------- */
void AngleSDK::write_data(FILE *fp)
{
for (int i = 1; i <= atom->nangletypes; i++)
fprintf(fp,"%d %g %g\n",i,k[i],theta0[i]/MY_PI*180.0);
}
/* ---------------------------------------------------------------------- */
void AngleSDK::ev_tally13(int i, int j, int nlocal, int newton_bond,
double evdwl, double fpair,
double delx, double dely, double delz)
{
double v[6];
if (eflag_either) {
if (eflag_global) {
if (newton_bond) {
energy += evdwl;
} else {
if (i < nlocal)
energy += 0.5*evdwl;
if (j < nlocal)
energy += 0.5*evdwl;
}
}
if (eflag_atom) {
if (newton_bond || i < nlocal) eatom[i] += 0.5*evdwl;
if (newton_bond || j < nlocal) eatom[j] += 0.5*evdwl;
}
}
if (vflag_either) {
v[0] = delx*delx*fpair;
v[1] = dely*dely*fpair;
v[2] = delz*delz*fpair;
v[3] = delx*dely*fpair;
v[4] = delx*delz*fpair;
v[5] = dely*delz*fpair;
if (vflag_global) {
if (newton_bond) {
virial[0] += v[0];
virial[1] += v[1];
virial[2] += v[2];
virial[3] += v[3];
virial[4] += v[4];
virial[5] += v[5];
} else {
if (i < nlocal) {
virial[0] += 0.5*v[0];
virial[1] += 0.5*v[1];
virial[2] += 0.5*v[2];
virial[3] += 0.5*v[3];
virial[4] += 0.5*v[4];
virial[5] += 0.5*v[5];
}
if (j < nlocal) {
virial[0] += 0.5*v[0];
virial[1] += 0.5*v[1];
virial[2] += 0.5*v[2];
virial[3] += 0.5*v[3];
virial[4] += 0.5*v[4];
virial[5] += 0.5*v[5];
}
}
}
if (vflag_atom) {
if (newton_bond || i < nlocal) {
vatom[i][0] += 0.5*v[0];
vatom[i][1] += 0.5*v[1];
vatom[i][2] += 0.5*v[2];
vatom[i][3] += 0.5*v[3];
vatom[i][4] += 0.5*v[4];
vatom[i][5] += 0.5*v[5];
}
if (newton_bond || j < nlocal) {
vatom[j][0] += 0.5*v[0];
vatom[j][1] += 0.5*v[1];
vatom[j][2] += 0.5*v[2];
vatom[j][3] += 0.5*v[3];
vatom[j][4] += 0.5*v[4];
vatom[j][5] += 0.5*v[5];
}
}
}
}
/* ---------------------------------------------------------------------- */
double AngleSDK::single(int type, int i1, int i2, int i3)
{
double **x = atom->x;
double delx1 = x[i1][0] - x[i2][0];
double dely1 = x[i1][1] - x[i2][1];
double delz1 = x[i1][2] - x[i2][2];
domain->minimum_image(delx1,dely1,delz1);
double r1 = sqrt(delx1*delx1 + dely1*dely1 + delz1*delz1);
double delx2 = x[i3][0] - x[i2][0];
double dely2 = x[i3][1] - x[i2][1];
double delz2 = x[i3][2] - x[i2][2];
domain->minimum_image(delx2,dely2,delz2);
double r2 = sqrt(delx2*delx2 + dely2*dely2 + delz2*delz2);
double c = delx1*delx2 + dely1*dely2 + delz1*delz2;
c /= r1*r2;
if (c > 1.0) c = 1.0;
if (c < -1.0) c = -1.0;
double e13=0.0;
if (repflag) {
// 1-3 LJ interaction.
double delx3 = x[i1][0] - x[i3][0];
double dely3 = x[i1][1] - x[i3][1];
double delz3 = x[i1][2] - x[i3][2];
domain->minimum_image(delx3,dely3,delz3);
const int type1 = atom->type[i1];
const int type3 = atom->type[i3];
const double rsq3 = delx3*delx3 + dely3*dely3 + delz3*delz3;
if (rsq3 < rminsq[type1][type3]) {
const int ljt = lj_type[type1][type3];
const double r2inv = 1.0/rsq3;
if (ljt == LJ12_4) {
const double r4inv=r2inv*r2inv;
e13 = r4inv*(lj3[type1][type3]*r4inv*r4inv - lj4[type1][type3]);
} else if (ljt == LJ9_6) {
const double r3inv = r2inv*sqrt(r2inv);
const double r6inv = r3inv*r3inv;
e13 = r6inv*(lj3[type1][type3]*r3inv - lj4[type1][type3]);
} else if (ljt == LJ12_6) {
const double r6inv = r2inv*r2inv*r2inv;
e13 = r6inv*(lj3[type1][type3]*r6inv - lj4[type1][type3]);
}
// make sure energy is 0.0 at the cutoff.
e13 -= emin[type1][type3];
}
}
double dtheta = acos(c) - theta0[type];
double tk = k[type] * dtheta;
return tk*dtheta + e13;
}

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