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pair_vashishta.cpp
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pair_vashishta.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: Yongnan Xiong (HNU), xyn@hnu.edu.cn
			Aidan Thompson (SNL)
			Anders Hafreager (UiO), andershaf@gmail.com
			------------------------------------------------------------------------- */

			#include <math.h>
			#include <stdio.h>
			#include <stdlib.h>
			#include <string.h>
			#include "pair_vashishta.h"
			#include "atom.h"
			#include "neighbor.h"
			#include "neigh_request.h"
			#include "force.h"
			#include "comm.h"
			#include "memory.h"
			#include "neighbor.h"
			#include "neigh_list.h"
			#include "memory.h"
			#include "error.h"
			using namespace LAMMPS_NS;

			#define MAXLINE 1024
			#define DELTA 4

			/* ---------------------------------------------------------------------- */

			PairVashishta::PairVashishta(LAMMPS *lmp) : Pair(lmp)
			{
			single_enable = 0;
			restartinfo = 0;
			one_coeff = 1;
			manybody_flag = 1;

			nelements = 0;
			elements = NULL;
			nparams = maxparam = 0;
			params = NULL;
			elem2param = NULL;
			map = NULL;

			neigh3BodyMax = 0;
			neigh3BodyCount = NULL;
			neigh3Body = NULL;

			useTable = false;
			nTablebits = 12;
			forceTable = NULL;
			potentialTable = NULL;
			}

			/* ----------------------------------------------------------------------
			check if allocated, since class can be destructed when incomplete
			------------------------------------------------------------------------- */

			PairVashishta::~PairVashishta()
			{
			if (elements)
			for (int i = 0; i < nelements; i++) delete [] elements[i];
			delete [] elements;
			memory->destroy(params);
			memory->destroy(elem2param);

			memory->destroy(forceTable);
			memory->destroy(potentialTable);
			memory->destroy(neigh3BodyCount);
			memory->destroy(neigh3Body);

			if (allocated) {
			memory->destroy(setflag);
			memory->destroy(cutsq);
			delete [] map;
			}
			}

			void PairVashishta::modify_params(int narg, char **arg)
			{
			if (narg == 0) error->all(FLERR,"Illegal pair_modify command");

			int iarg = 0;
			while (iarg < narg) {
			if (strcmp(arg[iarg],"table") == 0) {
			if (iarg+2 > narg) error->all(FLERR,"Illegal pair_modify command");

			nTablebits = force->inumeric(FLERR,arg[iarg+1]);
			if ((nTablebits < 0) \|\| (nTablebits > sizeof(int)*CHAR_BIT-1))
			error->all(FLERR,"Illegal interpolation table size");

			if (nTablebits == 0) {
			useTable = false;
			} else {
			useTable = true;
			}

			iarg += 2;
			} else if (strcmp(arg[iarg],"tabinner") == 0) {
			if (iarg+2 > narg) error->all(FLERR,"Illegal pair_modify command");

			tabinner = force->numeric(FLERR,arg[iarg+1]);
			if (tabinner <= 0.0)
			error->all(FLERR,"Illegal inner cutoff for tabulation");
			iarg += 2;
			}
			}
			updateTables();
			}

			void PairVashishta::validateNeigh3Body() {
			if (atom->nlocal > neigh3BodyMax) {
			neigh3BodyMax = atom->nmax;
			memory->destroy(neigh3BodyCount);
			memory->destroy(neigh3Body);
			memory->create(neigh3BodyCount,neigh3BodyMax, "pair:vashishta:neigh3BodyCount");
			memory->create(neigh3Body,neigh3BodyMax, 1000, "pair:vashishta:neigh3Body"); // TODO: pick this number more wisely?
			}
			}

			void PairVashishta::updateTables()
			{
			memory->destroy(forceTable);
			memory->destroy(potentialTable);
			forceTable = NULL;
			potentialTable = NULL;

			if (!useTable) return;

			int ntable = 1<<nTablebits;
			tabinnersq = tabinner*tabinner;

			deltaR2 = (cutmax*cutmax - tabinnersq) / (ntable-1);
			oneOverDeltaR2 = 1.0/deltaR2;

			memory->create(forceTable,nelements,nelements,ntable+1,"pair:vashishta:forceTable");
			memory->create(potentialTable,nelements,nelements,ntable+1,"pair:vashishta:potentialTable");

			for (int i = 0; i < nelements; i++) {
			for (int j = 0; j < nelements; j++) {
			int ijparam = elem2param[i][j][j];
			for(int idx=0; idx <= ntable; idx++) {
			double rsq = tabinnersq + idx*deltaR2;
			double fpair, eng;
			// call analytical version of two-body term function
			twobody(params[ijparam], rsq, fpair, 1, eng, false);
			forceTable[i][j][idx] = fpair;
			potentialTable[i][j][idx] = eng;
			}
			}
			}
			}

			/* ---------------------------------------------------------------------- */

			void PairVashishta::compute(int eflag, int vflag)
			{
			validateNeigh3Body();
			int i,j,k,ii,jj,kk,inum,jnum,jnumm1;
			int itype,jtype,ktype,ijparam,ikparam,ijkparam;
			tagint itag,jtag;
			double xtmp,ytmp,ztmp,delx,dely,delz,evdwl,fpair;
			double rsq,rsq1,rsq2;
			double delr1[3],delr2[3],fj[3],fk[3];
			int ilist,jlist,numneigh,*firstneigh;

			evdwl = 0.0;
			if (eflag \|\| vflag) ev_setup(eflag,vflag);
			else evflag = vflag_fdotr = 0;

			double **x = atom->x;
			double **f = atom->f;
			tagint *tag = atom->tag;
			int *type = atom->type;
			int nlocal = atom->nlocal;
			int newton_pair = force->newton_pair;

			inum = list->inum;
			ilist = list->ilist;
			numneigh = list->numneigh;
			firstneigh = list->firstneigh;

			// loop over full neighbor list of my atoms

			for (ii = 0; ii < inum; ii++) {
			i = ilist[ii];
			itag = tag[i];
			itype = map[type[i]];
			xtmp = x[i][0];
			ytmp = x[i][1];
			ztmp = x[i][2];

			neigh3BodyCount[i] = 0; // Reset the 3-body neighbor list

			// two-body interactions, skip half of them

			jlist = firstneigh[i];
			jnum = numneigh[i];

			for (jj = 0; jj < jnum; jj++) {
			j = jlist[jj];
			j &= NEIGHMASK;
			jtag = tag[j];

			jtype = map[type[j]];

			delx = xtmp - x[j][0];
			dely = ytmp - x[j][1];
			delz = ztmp - x[j][2];
			rsq = delxdelx + delydely + delz*delz;
			ijparam = elem2param[itype][jtype][jtype];

			if (rsq <= params[ijparam].cutsq2) {
			neigh3Body[i][neigh3BodyCount[i]] = j;
			neigh3BodyCount[i]++;
			}

			if (rsq > params[ijparam].cutsq) continue;

			if (itag > jtag) {
			if ((itag+jtag) % 2 == 0) continue;
			} else if (itag < jtag) {
			if ((itag+jtag) % 2 == 1) continue;
			} else {
			if (x[j][2] < ztmp) continue;
			if (x[j][2] == ztmp && x[j][1] < ytmp) continue;
			if (x[j][2] == ztmp && x[j][1] == ytmp && x[j][0] < xtmp) continue;
			}

			twobody(params[ijparam],rsq,fpair,eflag,evdwl, useTable);

			f[i][0] += delx*fpair;
			f[i][1] += dely*fpair;
			f[i][2] += delz*fpair;
			f[j][0] -= delx*fpair;
			f[j][1] -= dely*fpair;
			f[j][2] -= delz*fpair;

			if (evflag) ev_tally(i,j,nlocal,newton_pair,
			evdwl,0.0,fpair,delx,dely,delz);
			}

			jlist = neigh3Body[i];
			jnum = neigh3BodyCount[i];
			jnumm1 = jnum - 1;

			for (jj = 0; jj < jnumm1; jj++) {
			j = jlist[jj];
			j &= NEIGHMASK;
			jtype = map[type[j]];
			ijparam = elem2param[itype][jtype][jtype];
			delr1[0] = x[j][0] - xtmp;
			delr1[1] = x[j][1] - ytmp;
			delr1[2] = x[j][2] - ztmp;
			rsq1 = delr1[0]delr1[0] + delr1[1]delr1[1] + delr1[2]*delr1[2];
			if (rsq1 >= params[ijparam].cutsq2) continue;

			for (kk = jj+1; kk < jnum; kk++) {
			k = jlist[kk];
			k &= NEIGHMASK;
			ktype = map[type[k]];
			ikparam = elem2param[itype][ktype][ktype];
			ijkparam = elem2param[itype][jtype][ktype];

			delr2[0] = x[k][0] - xtmp;
			delr2[1] = x[k][1] - ytmp;
			delr2[2] = x[k][2] - ztmp;
			rsq2 = delr2[0]delr2[0] + delr2[1]delr2[1] + delr2[2]*delr2[2];
			if (rsq2 >= params[ikparam].cutsq2) continue;

			threebody(&params[ijparam],&params[ikparam],&params[ijkparam],
			rsq1,rsq2,delr1,delr2,fj,fk,eflag,evdwl);

			f[i][0] -= fj[0] + fk[0];
			f[i][1] -= fj[1] + fk[1];
			f[i][2] -= fj[2] + fk[2];
			f[j][0] += fj[0];
			f[j][1] += fj[1];
			f[j][2] += fj[2];
			f[k][0] += fk[0];
			f[k][1] += fk[1];
			f[k][2] += fk[2];

			if (evflag) ev_tally3(i,j,k,evdwl,0.0,fj,fk,delr1,delr2);
			}
			}
			}

			if (vflag_fdotr) virial_fdotr_compute();
			}

			/* ---------------------------------------------------------------------- */

			void PairVashishta::allocate()
			{
			allocated = 1;
			int n = atom->ntypes;

			memory->create(setflag,n+1,n+1,"pair:setflag");
			memory->create(cutsq,n+1,n+1,"pair:cutsq");

			map = new int[n+1];
			}

			/* ----------------------------------------------------------------------
			global settings
			------------------------------------------------------------------------- */

			void PairVashishta::settings(int narg, char **arg)
			{
			if (narg != 0) error->all(FLERR,"Illegal pair_style command");
			}

			/* ----------------------------------------------------------------------
			set coeffs for one or more type pairs
			------------------------------------------------------------------------- */

			void PairVashishta::coeff(int narg, char **arg)
			{
			int i,j,n;

			if (!allocated) allocate();

			if (narg != 3 + atom->ntypes)
			error->all(FLERR,"Incorrect args for pair coefficients");

			// insure I,J args are * *

			if (strcmp(arg[0],"") != 0 \|\| strcmp(arg[1],"") != 0)
			error->all(FLERR,"Incorrect args for pair coefficients");

			// read args that map atom types to elements in potential file
			// map[i] = which element the Ith atom type is, -1 if NULL
			// nelements = # of unique elements
			// elements = list of element names

			if (elements) {
			for (i = 0; i < nelements; i++) delete [] elements[i];
			delete [] elements;
			}
			elements = new char*[atom->ntypes];
			for (i = 0; i < atom->ntypes; i++) elements[i] = NULL;

			nelements = 0;
			for (i = 3; i < narg; i++) {
			if (strcmp(arg[i],"NULL") == 0) {
			map[i-2] = -1;
			continue;
			}
			for (j = 0; j < nelements; j++)
			if (strcmp(arg[i],elements[j]) == 0) break;
			map[i-2] = j;
			if (j == nelements) {
			n = strlen(arg[i]) + 1;
			elements[j] = new char[n];
			strcpy(elements[j],arg[i]);
			nelements++;
			}
			}

			// read potential file and initialize potential parameters

			read_file(arg[2]);
			setup_params();

			// clear setflag since coeff() called once with I,J = * *

			n = atom->ntypes;
			for (int i = 1; i <= n; i++)
			for (int j = i; j <= n; j++)
			setflag[i][j] = 0;

			// set setflag i,j for type pairs where both are mapped to elements

			int count = 0;
			for (int i = 1; i <= n; i++)
			for (int j = i; j <= n; j++)
			if (map[i] >= 0 && map[j] >= 0) {
			setflag[i][j] = 1;
			count++;
			}

			if (count == 0) error->all(FLERR,"Incorrect args for pair coefficients");
			}

			/* ----------------------------------------------------------------------
			init specific to this pair style
			------------------------------------------------------------------------- */

			void PairVashishta::init_style()
			{
			if (atom->tag_enable == 0)
			error->all(FLERR,"Pair style Vashishta requires atom IDs");
			if (force->newton_pair == 0)
			error->all(FLERR,"Pair style Vashishta requires newton pair on");

			// need a full neighbor list

			int irequest = neighbor->request(this);
			neighbor->requests[irequest]->half = 0;
			neighbor->requests[irequest]->full = 1;
			}

			/* ----------------------------------------------------------------------
			init for one type pair i,j and corresponding j,i
			------------------------------------------------------------------------- */

			double PairVashishta::init_one(int i, int j)
			{
			if (setflag[i][j] == 0) error->all(FLERR,"All pair coeffs are not set");

			return cutmax;
			}

			/* ---------------------------------------------------------------------- */

			void PairVashishta::read_file(char *file)
			{
			int params_per_line = 17;
			char *words = new char[params_per_line+1];

			memory->sfree(params);
			params = NULL;
			nparams = maxparam = 0;

			// open file on proc 0

			FILE *fp;
			if (comm->me == 0) {
			fp = force->open_potential(file);
			if (fp == NULL) {
			char str[128];
			sprintf(str,"Cannot open Vashishta potential file %s",file);
			error->one(FLERR,str);
			}
			}

			// read each set of params from potential file
			// one set of params can span multiple lines
			// store params if all 3 element tags are in element list

			int n,nwords,ielement,jelement,kelement;
			char line[MAXLINE],*ptr;
			int eof = 0;

			while (1) {
			if (comm->me == 0) {
			ptr = fgets(line,MAXLINE,fp);
			if (ptr == NULL) {
			eof = 1;
			fclose(fp);
			} else n = strlen(line) + 1;
			}
			MPI_Bcast(&eof,1,MPI_INT,0,world);
			if (eof) break;
			MPI_Bcast(&n,1,MPI_INT,0,world);
			MPI_Bcast(line,n,MPI_CHAR,0,world);

			// strip comment, skip line if blank

			if ((ptr = strchr(line,'#'))) *ptr = '\0';
			nwords = atom->count_words(line);
			if (nwords == 0) continue;

			// concatenate additional lines until have params_per_line words

			while (nwords < params_per_line) {
			n = strlen(line);
			if (comm->me == 0) {
			ptr = fgets(&line[n],MAXLINE-n,fp);
			if (ptr == NULL) {
			eof = 1;
			fclose(fp);
			} else n = strlen(line) + 1;
			}
			MPI_Bcast(&eof,1,MPI_INT,0,world);
			if (eof) break;
			MPI_Bcast(&n,1,MPI_INT,0,world);
			MPI_Bcast(line,n,MPI_CHAR,0,world);
			if ((ptr = strchr(line,'#'))) *ptr = '\0';
			nwords = atom->count_words(line);
			}

			if (nwords != params_per_line)
			error->all(FLERR,"Incorrect format in Vashishta potential file");

			// words = ptrs to all words in line

			nwords = 0;
			words[nwords++] = strtok(line," \t\n\r\f");
			while ((words[nwords++] = strtok(NULL," \t\n\r\f"))) continue;

			// ielement,jelement,kelement = 1st args
			// if all 3 args are in element list, then parse this line
			// else skip to next entry in file

			for (ielement = 0; ielement < nelements; ielement++)
			if (strcmp(words[0],elements[ielement]) == 0) break;
			if (ielement == nelements) continue;
			for (jelement = 0; jelement < nelements; jelement++)
			if (strcmp(words[1],elements[jelement]) == 0) break;
			if (jelement == nelements) continue;
			for (kelement = 0; kelement < nelements; kelement++)
			if (strcmp(words[2],elements[kelement]) == 0) break;
			if (kelement == nelements) continue;

			// load up parameter settings and error check their values

			if (nparams == maxparam) {
			maxparam += DELTA;
			params = (Param ) memory->srealloc(params,maxparamsizeof(Param),
			"pair:params");
			}

			params[nparams].ielement = ielement;
			params[nparams].jelement = jelement;
			params[nparams].kelement = kelement;
			params[nparams].bigh = atof(words[3]);
			params[nparams].eta = atof(words[4]);
			params[nparams].zi = atof(words[5]);
			params[nparams].zj = atof(words[6]);
			params[nparams].lambda1 = atof(words[7]);
			params[nparams].bigd = atof(words[8]);
			params[nparams].lambda4 = atof(words[9]);
			params[nparams].bigw = atof(words[10]);
			params[nparams].cut = atof(words[11]);
			params[nparams].bigb = atof(words[12]);
			params[nparams].gamma = atof(words[13]);
			params[nparams].r0 = atof(words[14]);
			params[nparams].bigc = atof(words[15]);
			params[nparams].costheta = atof(words[16]);

			if (params[nparams].bigb < 0.0 \|\| params[nparams].gamma < 0.0 \|\|
			params[nparams].r0 < 0.0 \|\| params[nparams].bigc < 0.0 \|\|
			params[nparams].bigh < 0.0 \|\| params[nparams].eta < 0.0 \|\|
			params[nparams].lambda1 < 0.0 \|\| params[nparams].bigd < 0.0 \|\|
			params[nparams].lambda4 < 0.0 \|\| params[nparams].bigw < 0.0 \|\|
			params[nparams].cut < 0.0)
			error->all(FLERR,"Illegal Vashishta parameter");

			nparams++;
			}

			delete [] words;
			}

			/* ---------------------------------------------------------------------- */

			void PairVashishta::setup_params()
			{
			int i,j,k,m,n;

			// set elem2param for all triplet combinations
			// must be a single exact match to lines read from file
			// do not allow for ACB in place of ABC

			memory->destroy(elem2param);
			memory->create(elem2param,nelements,nelements,nelements,"pair:elem2param");

			for (i = 0; i < nelements; i++)
			for (j = 0; j < nelements; j++)
			for (k = 0; k < nelements; k++) {
			n = -1;
			for (m = 0; m < nparams; m++) {
			if (i == params[m].ielement && j == params[m].jelement &&
			k == params[m].kelement) {
			if (n >= 0) error->all(FLERR,"Potential file has duplicate entry");
			n = m;
			}
			}
			if (n < 0) error->all(FLERR,"Potential file is missing an entry");
			elem2param[i][j][k] = n;
			}

			// compute parameter values derived from inputs

			// set cutsq using shortcut to reduce neighbor list for accelerated
			// calculations. cut must remain unchanged as it is a potential parameter
			double tmp_par;

			for (m = 0; m < nparams; m++) {
			params[m].cutsq = params[m].cut * params[m].cut;
			params[m].cutsq2 = params[m].r0 * params[m].r0;

			tmp_par = params[m].lambda1;
			params[m].lam1inv = (tmp_par == 0.0) ? 0.0 : 1.0/tmp_par;
			tmp_par = params[m].lambda4;
			params[m].lam4inv = (tmp_par == 0.0) ? 0.0 : 1.0/tmp_par;
			params[m].zizj = params[m].ziparams[m].zj force->qqr2e;
			// note that bigd does not have 1/2 factor
			params[m].mbigd = params[m].bigd;
			params[m].heta = params[m].bigh*params[m].eta;
			params[m].big2b = 2.0*params[m].bigb;
			params[m].big6w = 6.0*params[m].bigw;

			tmp_par = params[m].cut;
			params[m].rcinv = (tmp_par == 0.0) ? 0.0 : 1.0/tmp_par;
			params[m].rc2inv = params[m].rcinv*params[m].rcinv;
			params[m].rc4inv = params[m].rc2inv*params[m].rc2inv;
			params[m].rc6inv = params[m].rc2inv*params[m].rc4inv;
			params[m].rceta = pow(params[m].rcinv,params[m].eta);
			params[m].lam1rc = params[m].cut*params[m].lam1inv;
			params[m].lam4rc = params[m].cut*params[m].lam4inv;
			params[m].vrcc2 = params[m].zizjparams[m].rcinv
			exp(-params[m].lam1rc);
			params[m].vrcc3 = params[m].mbigdparams[m].rc4inv
			exp(-params[m].lam4rc);
			params[m].vrc = params[m].bigh*params[m].rceta +
			params[m].vrcc2 - params[m].vrcc3 -
			params[m].bigw*params[m].rc6inv;

			params[m].dvrc =
			params[m].vrcc3 * (4.0*params[m].rcinv+params[m].lam4inv)
			+ params[m].big6w * params[m].rc6inv * params[m].rcinv
			- params[m].heta * params[m].rceta*params[m].rcinv
			- params[m].vrcc2 * (params[m].rcinv+params[m].lam1inv);
			params[m].c0 = params[m].cut*params[m].dvrc - params[m].vrc;
			}

			// set cutmax to max of all params

			cutmax = 0.0;
			for (m = 0; m < nparams; m++) {
			if (params[m].cut > cutmax) cutmax = params[m].cut;
			if (params[m].r0 > cutmax) cutmax = params[m].r0;
			}

			updateTables();
			}

			/* ---------------------------------------------------------------------- */

			void PairVashishta::twobody(const Param &param, double rsq, double &fforce,
			int eflag, double &eng, bool tabulated)
			{
			if (tabulated) {
			if (rsq < tabinnersq) {
			sprintf(estr,"Pair distance < table inner cutoff: "
			"ijtype %d %d dist %g",param.ielement+1,param.jelement+1,sqrt(rsq));
			error->one(FLERR,estr);
			}

			const int tableIndex = (rsq - tabinnersq)*oneOverDeltaR2;
			// double - int will only keep the 0.xxxx part
			const double fraction = (rsq - tabinnersq)*oneOverDeltaR2 - tableIndex;

			double force0 = forceTable[param.ielement][param.jelement][tableIndex];
			double force1 = forceTable[param.ielement][param.jelement][tableIndex+1];
			fforce = (1.0 - fraction)force0 + fractionforce1; // force is linearly interpolated between the two values
			if (evflag) {
			double energy0 = potentialTable[param.ielement][param.jelement][tableIndex];
			double energy1 = potentialTable[param.ielement][param.jelement][tableIndex+1];
			eng = (1.0 - fraction)energy0 + fractionenergy1;
			}
			} else {
			double r,rinvsq,r4inv,r6inv,reta,lam1r,lam4r,vc2,vc3;

			r = sqrt(rsq);
			rinvsq = 1.0/rsq;
			r4inv = rinvsq*rinvsq;
			r6inv = rinvsq*r4inv;
			reta = pow(r,-param.eta);
			lam1r = r*param.lam1inv;
			lam4r = r*param.lam4inv;
			vc2 = param.zizj * exp(-lam1r)/r;
			vc3 = param.mbigd * r4inv*exp(-lam4r);

			fforce = (param.dvrc*r
			- (4.0vc3 + lam4rvc3+param.big6w*r6inv
			- param.hetareta - vc2 - lam1rvc2)
			) * rinvsq;
			if (eflag) eng = param.bigh*reta
			+ vc2 - vc3 - param.bigw*r6inv
			- r*param.dvrc + param.c0;
			}
			}

			/* ---------------------------------------------------------------------- */

			void PairVashishta::threebody(Param paramij, Param paramik, Param *paramijk,
			double rsq1, double rsq2,
			double delr1, double delr2,
			double fj, double fk, int eflag, double &eng)
			{
			double r1,rinvsq1,rainv1,gsrainv1,gsrainvsq1,expgsrainv1;
			double r2,rinvsq2,rainv2,gsrainv2,gsrainvsq2,expgsrainv2;
			double rinv12,cs,delcs,delcssq,facexp,facrad,frad1,frad2,pcsinv,pcsinvsq,pcs;
			double facang,facang12,csfacang,csfac1,csfac2;

			r1 = sqrt(rsq1);
			rinvsq1 = 1.0/rsq1;
			rainv1 = 1.0/(r1 - paramij->r0);
			gsrainv1 = paramij->gamma * rainv1;
			gsrainvsq1 = gsrainv1*rainv1/r1;
			expgsrainv1 = exp(gsrainv1);

			r2 = sqrt(rsq2);
			rinvsq2 = 1.0/rsq2;
			rainv2 = 1.0/(r2 - paramik->r0);
			gsrainv2 = paramik->gamma * rainv2;
			gsrainvsq2 = gsrainv2*rainv2/r2;
			expgsrainv2 = exp(gsrainv2);

			rinv12 = 1.0/(r1*r2);
			cs = (delr1[0]delr2[0] + delr1[1]delr2[1] + delr1[2]delr2[2]) rinv12;
			delcs = cs - paramijk->costheta;
			delcssq = delcs*delcs;
			pcsinv = paramijk->bigc*delcssq + 1.0;
			pcsinvsq = pcsinv*pcsinv;
			pcs = delcssq/pcsinv;

			facexp = expgsrainv1*expgsrainv2;

			facrad = paramijk->bigb * facexp * pcs;
			frad1 = facrad*gsrainvsq1;
			frad2 = facrad*gsrainvsq2;
			facang = paramijk->big2b * facexp * delcs/pcsinvsq;
			facang12 = rinv12*facang;
			csfacang = cs*facang;
			csfac1 = rinvsq1*csfacang;

			fj[0] = delr1[0](frad1+csfac1)-delr2[0]facang12;
			fj[1] = delr1[1](frad1+csfac1)-delr2[1]facang12;
			fj[2] = delr1[2](frad1+csfac1)-delr2[2]facang12;

			csfac2 = rinvsq2*csfacang;

			fk[0] = delr2[0](frad2+csfac2)-delr1[0]facang12;
			fk[1] = delr2[1](frad2+csfac2)-delr1[1]facang12;
			fk[2] = delr2[2](frad2+csfac2)-delr1[2]facang12;

			if (eflag) eng = facrad;
			}

			/* ----------------------------------------------------------------------
			* add memory usage for tabulation
			* ---------------------------------------------------------------------- */

			double PairVashishta::memory_usage()
			{
			double bytes = Pair::memory_usage();
			if (useTable)
			bytes += 2nelementsnelementssizeof(double)(1<<nTablebits);
			return bytes;
			}

lammps/src/MANYBODY/pair_vashishta.cpp214494477854lammm-master-deprecated

pair_vashishta.cppView Options

lammps/src/MANYBODY/pair_vashishta.cpp
214494477854lammm-master-deprecated

pair_vashishta.cpp
View Options