pair_edip.cpp
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Created: Wed, Jun 5, 21:12

pair_edip.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: Luca Ferraro (CASPUR)
	email: luca.ferraro@caspur.it

	Environment Dependent Interatomic Potential
	References:
	1) J. F. Justo, M. Z. Bazant, E. Kaxiras, V. V. Bulatov, S. Yip
	Phys. Rev. B 58, 2539 (1998)
	------------------------------------------------------------------------- */

	#include "math.h"
	#include "float.h"
	#include "stdio.h"
	#include "stdlib.h"
	#include "string.h"
	#include "pair_edip.h"
	#include "atom.h"
	#include "neighbor.h"
	#include "neigh_list.h"
	#include "neigh_request.h"
	#include "force.h"
	#include "comm.h"
	#include "memory.h"
	#include "error.h"

	using namespace LAMMPS_NS;

	#define MAXLINE 1024
	#define DELTA 4

	#define GRIDDENSITY 8000
	#define GRIDSTART 0.1

	// max number of interaction per atom for f(Z) environment potential

	#define leadDimInteractionList 64

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

	PairEDIP::PairEDIP(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;
	}

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

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

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

	deallocateGrids();
	deallocatePreLoops();
	}
	}

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

	void PairEDIP::compute(int eflag, int vflag)
	{
	int i,j,k,ii,inum,jnum;
	int itype,jtype,ktype,ijparam,ikparam;
	double xtmp,ytmp,ztmp,evdwl;
	int ilist,jlist,numneigh,*firstneigh;
	register int preForceCoord_counter;

	double invR_ij;
	double invR_ik;
	double directorCos_ij_x;
	double directorCos_ij_y;
	double directorCos_ij_z;
	double directorCos_ik_x;
	double directorCos_ik_y;
	double directorCos_ik_z;
	double cosTeta;

	int interpolIDX;
	double interpolTMP;
	double interpolDeltaX;
	double interpolY1;
	double interpolY2;

	double invRMinusCutoffA;
	double sigmaInvRMinusCutoffA;
	double gammInvRMinusCutoffA;
	double cosTetaDiff;
	double cosTetaDiffCosTetaDiff;
	double cutoffFunction_ij;
	double exp2B_ij;
	double exp2BDerived_ij;
	double pow2B_ij;
	double pow2BDerived_ij;
	double exp3B_ij;
	double exp3BDerived_ij;
	double exp3B_ik;
	double exp3BDerived_ik;
	double qFunction;
	double tauFunction;
	double tauFunctionDerived;
	double expMinusBetaZeta_iZeta_i;
	double qFunctionCosTetaDiffCosTetaDiff;
	double expMinusQFunctionCosTetaDiffCosTetaDiff;
	double zeta_i;
	double zeta_iDerived;
	double zeta_iDerivedInvR_ij;

	double forceModCoord_factor;
	double forceModCoord;
	double forceModCoord_ij;
	double forceMod2B;
	double forceMod3B_factor1_ij;
	double forceMod3B_factor2_ij;
	double forceMod3B_factor2;
	double forceMod3B_factor1_ik;
	double forceMod3B_factor2_ik;
	double potentia3B_factor;
	double potential2B_factor;

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

	double **x = atom->x;
	double **f = atom->f;
	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++) {
	zeta_i = 0.0;
	int numForceCoordPairs = 0;

	i = ilist[ii];
	itype = map[type[i]];
	xtmp = x[i][0];
	ytmp = x[i][1];
	ztmp = x[i][2];

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

	// pre-loop to compute environment coordination f(Z)

	for (int neighbor_j = 0; neighbor_j < jnum; neighbor_j++) {
	j = jlist[neighbor_j];
	j &= NEIGHMASK;

	double dr_ij[3], r_ij;

	dr_ij[0] = xtmp - x[j][0];
	dr_ij[1] = ytmp - x[j][1];
	dr_ij[2] = ztmp - x[j][2];
	r_ij = dr_ij[0]dr_ij[0] + dr_ij[1]dr_ij[1] + dr_ij[2]*dr_ij[2];

	jtype = map[type[j]];
	ijparam = elem2param[itype][jtype][jtype];
	if (r_ij > params[ijparam].cutsq) continue;

	r_ij = sqrt(r_ij);

	invR_ij = 1.0 / r_ij;
	preInvR_ij[neighbor_j] = invR_ij;

	invRMinusCutoffA = 1.0 / (r_ij - cutoffA);
	sigmaInvRMinusCutoffA = sigma * invRMinusCutoffA;
	gammInvRMinusCutoffA = gamm * invRMinusCutoffA;

	interpolDeltaX = r_ij - GRIDSTART;
	interpolTMP = (interpolDeltaX * GRIDDENSITY);
	interpolIDX = (int) interpolTMP;

	interpolY1 = exp3B[interpolIDX];
	interpolY2 = exp3B[interpolIDX+1];
	exp3B_ij = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	exp3BDerived_ij = - exp3B_ij * gammInvRMinusCutoffA * invRMinusCutoffA;

	preExp3B_ij[neighbor_j] = exp3B_ij;
	preExp3BDerived_ij[neighbor_j] = exp3BDerived_ij;

	interpolY1 = exp2B[interpolIDX];
	interpolY2 = exp2B[interpolIDX+1];
	exp2B_ij = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	exp2BDerived_ij = - exp2B_ij * sigmaInvRMinusCutoffA * invRMinusCutoffA;

	preExp2B_ij[neighbor_j] = exp2B_ij;
	preExp2BDerived_ij[neighbor_j] = exp2BDerived_ij;

	interpolY1 = pow2B[interpolIDX];
	interpolY2 = pow2B[interpolIDX+1];
	pow2B_ij = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	prePow2B_ij[neighbor_j] = pow2B_ij;

	// zeta and its derivative

	if (r_ij < cutoffC) zeta_i += 1.0;
	else {
	interpolY1 = cutoffFunction[interpolIDX];
	interpolY2 = cutoffFunction[interpolIDX+1];
	cutoffFunction_ij = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	zeta_i += cutoffFunction_ij;

	interpolY1 = cutoffFunctionDerived[interpolIDX];
	interpolY2 = cutoffFunctionDerived[interpolIDX+1];
	zeta_iDerived = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	zeta_iDerivedInvR_ij = zeta_iDerived * invR_ij;

	preForceCoord_counter=numForceCoordPairs*5;
	preForceCoord[preForceCoord_counter+0]=zeta_iDerivedInvR_ij;
	preForceCoord[preForceCoord_counter+1]=dr_ij[0];
	preForceCoord[preForceCoord_counter+2]=dr_ij[1];
	preForceCoord[preForceCoord_counter+3]=dr_ij[2];
	preForceCoord[preForceCoord_counter+4]=j;
	numForceCoordPairs++;
	}
	}

	// quantities depending on zeta_i

	interpolDeltaX = zeta_i;
	interpolTMP = (interpolDeltaX * GRIDDENSITY);
	interpolIDX = (int) interpolTMP;

	interpolY1 = expMinusBetaZeta_iZeta_iGrid[interpolIDX];
	interpolY2 = expMinusBetaZeta_iZeta_iGrid[interpolIDX+1];
	expMinusBetaZeta_iZeta_i = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	interpolY1 = qFunctionGrid[interpolIDX];
	interpolY2 = qFunctionGrid[interpolIDX+1];
	qFunction = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	interpolY1 = tauFunctionGrid[interpolIDX];
	interpolY2 = tauFunctionGrid[interpolIDX+1];
	tauFunction = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	interpolY1 = tauFunctionDerivedGrid[interpolIDX];
	interpolY2 = tauFunctionDerivedGrid[interpolIDX+1];
	tauFunctionDerived = interpolY1 + (interpolY2 - interpolY1) *
	(interpolTMP-interpolIDX);

	forceModCoord_factor = 2.0 * beta * zeta_i * expMinusBetaZeta_iZeta_i;

	forceModCoord = 0.0;

	// two-body interactions, skip half of them

	for (int neighbor_j = 0; neighbor_j < jnum; neighbor_j++) {
	double dr_ij[3], r_ij, f_ij[3];

	j = jlist[neighbor_j];
	j &= NEIGHMASK;

	dr_ij[0] = x[j][0] - xtmp;
	dr_ij[1] = x[j][1] - ytmp;
	dr_ij[2] = x[j][2] - ztmp;
	r_ij = dr_ij[0]dr_ij[0] + dr_ij[1]dr_ij[1] + dr_ij[2]*dr_ij[2];

	jtype = map[type[j]];
	ijparam = elem2param[itype][jtype][jtype];
	if (r_ij > params[ijparam].cutsq) continue;

	r_ij = sqrt(r_ij);

	invR_ij = preInvR_ij[neighbor_j];
	pow2B_ij = prePow2B_ij[neighbor_j];

	potential2B_factor = pow2B_ij - expMinusBetaZeta_iZeta_i;

	exp2B_ij = preExp2B_ij[neighbor_j];

	pow2BDerived_ij = - rho * invR_ij * pow2B_ij;

	forceModCoord += (forceModCoord_factor*exp2B_ij);

	exp2BDerived_ij = preExp2BDerived_ij[neighbor_j];
	forceMod2B = exp2BDerived_ij * potential2B_factor +
	exp2B_ij * pow2BDerived_ij;

	directorCos_ij_x = invR_ij * dr_ij[0];
	directorCos_ij_y = invR_ij * dr_ij[1];
	directorCos_ij_z = invR_ij * dr_ij[2];

	exp3B_ij = preExp3B_ij[neighbor_j];
	exp3BDerived_ij = preExp3BDerived_ij[neighbor_j];

	f_ij[0] = forceMod2B * directorCos_ij_x;
	f_ij[1] = forceMod2B * directorCos_ij_y;
	f_ij[2] = forceMod2B * directorCos_ij_z;

	f[i][0] += f_ij[0];
	f[i][1] += f_ij[1];
	f[i][2] += f_ij[2];

	f[j][0] -= f_ij[0];
	f[j][1] -= f_ij[1];
	f[j][2] -= f_ij[2];

	// potential energy

	evdwl = (exp2B_ij * potential2B_factor);

	if (evflag) ev_tally(i, j, nlocal, newton_pair, evdwl, 0.0,
	-forceMod2B*invR_ij, dr_ij[0], dr_ij[1], dr_ij[2]);

	// three-body Forces

	for (int neighbor_k = neighbor_j + 1; neighbor_k < jnum; neighbor_k++) {
	double dr_ik[3], r_ik, f_ik[3];

	k = jlist[neighbor_k];
	k &= NEIGHMASK;
	ktype = map[type[k]];
	ikparam = elem2param[itype][ktype][ktype];

	dr_ik[0] = x[k][0] - xtmp;
	dr_ik[1] = x[k][1] - ytmp;
	dr_ik[2] = x[k][2] - ztmp;
	r_ik = dr_ik[0]dr_ik[0] + dr_ik[1]dr_ik[1] + dr_ik[2]*dr_ik[2];

	if (r_ik > params[ikparam].cutsq) continue;

	r_ik = sqrt(r_ik);

	invR_ik = preInvR_ij[neighbor_k];

	directorCos_ik_x = invR_ik * dr_ik[0];
	directorCos_ik_y = invR_ik * dr_ik[1];
	directorCos_ik_z = invR_ik * dr_ik[2];

	cosTeta = directorCos_ij_x * directorCos_ik_x +
	directorCos_ij_y * directorCos_ik_y +
	directorCos_ij_z * directorCos_ik_z;

	cosTetaDiff = cosTeta + tauFunction;
	cosTetaDiffCosTetaDiff = cosTetaDiff * cosTetaDiff;
	qFunctionCosTetaDiffCosTetaDiff = cosTetaDiffCosTetaDiff * qFunction;
	expMinusQFunctionCosTetaDiffCosTetaDiff =
	exp(-qFunctionCosTetaDiffCosTetaDiff);

	potentia3B_factor = lambda *
	((1.0 - expMinusQFunctionCosTetaDiffCosTetaDiff) +
	eta * qFunctionCosTetaDiffCosTetaDiff);

	exp3B_ik = preExp3B_ij[neighbor_k];
	exp3BDerived_ik = preExp3BDerived_ij[neighbor_k];

	forceMod3B_factor1_ij = - exp3BDerived_ij * exp3B_ik *
	potentia3B_factor;
	forceMod3B_factor2 = 2.0 * lambda * exp3B_ij * exp3B_ik *
	qFunction * cosTetaDiff *
	(eta + expMinusQFunctionCosTetaDiffCosTetaDiff);
	forceMod3B_factor2_ij = forceMod3B_factor2 * invR_ij;

	f_ij[0] = forceMod3B_factor1_ij * directorCos_ij_x +
	forceMod3B_factor2_ij *
	(cosTeta * directorCos_ij_x - directorCos_ik_x);
	f_ij[1] = forceMod3B_factor1_ij * directorCos_ij_y +
	forceMod3B_factor2_ij *
	(cosTeta * directorCos_ij_y - directorCos_ik_y);
	f_ij[2] = forceMod3B_factor1_ij * directorCos_ij_z +
	forceMod3B_factor2_ij *
	(cosTeta * directorCos_ij_z - directorCos_ik_z);

	forceMod3B_factor1_ik = - exp3BDerived_ik * exp3B_ij *
	potentia3B_factor;
	forceMod3B_factor2_ik = forceMod3B_factor2 * invR_ik;

	f_ik[0] = forceMod3B_factor1_ik * directorCos_ik_x +
	forceMod3B_factor2_ik *
	(cosTeta * directorCos_ik_x - directorCos_ij_x);
	f_ik[1] = forceMod3B_factor1_ik * directorCos_ik_y +
	forceMod3B_factor2_ik *
	(cosTeta * directorCos_ik_y - directorCos_ij_y);
	f_ik[2] = forceMod3B_factor1_ik * directorCos_ik_z +
	forceMod3B_factor2_ik *
	(cosTeta * directorCos_ik_z - directorCos_ij_z);

	forceModCoord += (forceMod3B_factor2 *
	(tauFunctionDerived - 0.5 * mu * cosTetaDiff));

	f[j][0] += f_ij[0];
	f[j][1] += f_ij[1];
	f[j][2] += f_ij[2];

	f[k][0] += f_ik[0];
	f[k][1] += f_ik[1];
	f[k][2] += f_ik[2];

	f[i][0] -= f_ij[0] + f_ik[0];
	f[i][1] -= f_ij[1] + f_ik[1];
	f[i][2] -= f_ij[2] + f_ik[2];

	// potential energy

	evdwl = (exp3B_ij * exp3B_ik * potentia3B_factor);

	if (evflag) ev_tally3(i,j,k,evdwl,0.0,f_ij,f_ik,dr_ij,dr_ik);
	}
	}

	// forces due to environment coordination f(Z)

	for (int idx = 0; idx < numForceCoordPairs; idx++) {
	double dr_ij[3],f_ij[3];

	preForceCoord_counter = idx * 5;
	zeta_iDerivedInvR_ij=preForceCoord[preForceCoord_counter+0];
	dr_ij[0]=preForceCoord[preForceCoord_counter+1];
	dr_ij[1]=preForceCoord[preForceCoord_counter+2];
	dr_ij[2]=preForceCoord[preForceCoord_counter+3];
	j = static_cast<int> (preForceCoord[preForceCoord_counter+4]);

	forceModCoord_ij = forceModCoord * zeta_iDerivedInvR_ij;

	f_ij[0] = forceModCoord_ij * dr_ij[0];
	f_ij[1] = forceModCoord_ij * dr_ij[1];
	f_ij[2] = forceModCoord_ij * dr_ij[2];

	f[i][0] -= f_ij[0];
	f[i][1] -= f_ij[1];
	f[i][2] -= f_ij[2];

	f[j][0] += f_ij[0];
	f[j][1] += f_ij[1];
	f[j][2] += f_ij[2];

	// potential energy

	evdwl = 0.0;
	if (evflag) ev_tally(i, j, nlocal, newton_pair, evdwl, 0.0,
	-forceModCoord_ij, dr_ij[0], dr_ij[1], dr_ij[2]);
	}
	}

	if (vflag_fdotr) virial_fdotr_compute();
	}

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

	void PairEDIP::allocateGrids(void)
	{
	int numGridPointsOneCutoffFunction;
	int numGridPointsNotOneCutoffFunction;
	int numGridPointsCutoffFunction;
	int numGridPointsR;
	int numGridPointsRTotal;
	int numGridPointsQFunctionGrid;
	int numGridPointsExpMinusBetaZeta_iZeta_i;
	int numGridPointsTauFunctionGrid;
	double maxArgumentTauFunctionGrid;
	double maxArgumentQFunctionGrid;
	double maxArgumentExpMinusBetaZeta_iZeta_i;
	double const leftLimitToZero = -DBL_MIN * 1000.0;

	// tauFunctionGrid

	maxArgumentTauFunctionGrid = leadDimInteractionList;
	numGridPointsTauFunctionGrid = (int)
	((maxArgumentTauFunctionGrid) * GRIDDENSITY) + 2;

	memory->create(tauFunctionGrid,numGridPointsTauFunctionGrid,
	"edip:tauFunctionGrid");
	memory->create(tauFunctionDerivedGrid,numGridPointsTauFunctionGrid,
	"edip:tauFunctionDerivedGrid");

	// expMinusBetaZeta_iZeta_iGrid

	maxArgumentExpMinusBetaZeta_iZeta_i = leadDimInteractionList;
	numGridPointsExpMinusBetaZeta_iZeta_i = (int)
	((maxArgumentExpMinusBetaZeta_iZeta_i) * GRIDDENSITY) + 2;
	memory->create(expMinusBetaZeta_iZeta_iGrid,
	numGridPointsExpMinusBetaZeta_iZeta_i,
	"edip:expMinusBetaZeta_iZeta_iGrid");

	// qFunctionGrid

	maxArgumentQFunctionGrid = leadDimInteractionList;
	numGridPointsQFunctionGrid = (int)
	((maxArgumentQFunctionGrid) * GRIDDENSITY) + 2;
	memory->create(qFunctionGrid,numGridPointsQFunctionGrid,"edip:qFunctionGrid");

	// cutoffFunction

	numGridPointsOneCutoffFunction = (int) ((cutoffC - GRIDSTART) * GRIDDENSITY);
	numGridPointsNotOneCutoffFunction = (int) ((cutoffA-cutoffC) * GRIDDENSITY);
	numGridPointsCutoffFunction = numGridPointsOneCutoffFunction +
	numGridPointsNotOneCutoffFunction+2;

	memory->create(cutoffFunction,numGridPointsCutoffFunction,
	"edip:cutoffFunction");
	memory->create(cutoffFunctionDerived,numGridPointsCutoffFunction,
	"edip:cutoffFunctionDerived");

	// pow2B

	numGridPointsR = (int)
	((cutoffA + leftLimitToZero - GRIDSTART) * GRIDDENSITY);
	numGridPointsRTotal = numGridPointsR + 2;

	memory->create(pow2B,numGridPointsRTotal,"edip:pow2B");
	memory->create(exp2B,numGridPointsRTotal,"edip:exp2B");
	memory->create(exp3B,numGridPointsRTotal,"edip:exp3B");
	}

	/* ----------------------------------------------------------------------
	pre-calculated structures
	------------------------------------------------------------------------- */

	void PairEDIP::allocatePreLoops(void)
	{
	int nthreads = comm->nthreads;

	memory->create(preInvR_ij,nthreads*leadDimInteractionList,"edip:preInvR_ij");
	memory->create(preExp3B_ij,nthreads*leadDimInteractionList,"edip:preExp3B_ij");
	memory->create(preExp3BDerived_ij,nthreads*leadDimInteractionList,
	"edip:preExp3BDerived_ij");
	memory->create(preExp2B_ij,nthreads*leadDimInteractionList,"edip:preExp2B_ij");
	memory->create(preExp2BDerived_ij,nthreads*leadDimInteractionList,
	"edip:preExp2BDerived_ij");
	memory->create(prePow2B_ij,nthreads*leadDimInteractionList,"edip:prePow2B_ij");
	memory->create(preForceCoord,5nthreadsleadDimInteractionList,"edip:preForceCoord");
	}

	/* ----------------------------------------------------------------------
	deallocate grids
	------------------------------------------------------------------------- */

	void PairEDIP::deallocateGrids(void)
	{
	memory->destroy(cutoffFunction);
	memory->destroy(cutoffFunctionDerived);
	memory->destroy(pow2B);
	memory->destroy(exp2B);
	memory->destroy(exp3B);
	memory->destroy(qFunctionGrid);
	memory->destroy(expMinusBetaZeta_iZeta_iGrid);
	memory->destroy(tauFunctionGrid);
	memory->destroy(tauFunctionDerivedGrid);
	}

	/* ----------------------------------------------------------------------
	deallocate preLoops
	------------------------------------------------------------------------- */

	void PairEDIP::deallocatePreLoops(void)
	{
	memory->destroy(preInvR_ij);
	memory->destroy(preExp3B_ij);
	memory->destroy(preExp3BDerived_ij);
	memory->destroy(preExp2B_ij);
	memory->destroy(preExp2BDerived_ij);
	memory->destroy(prePow2B_ij);
	memory->destroy(preForceCoord);
	}

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

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

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

	void PairEDIP::initGrids(void)
	{
	int l;
	int numGridPointsOneCutoffFunction;
	int numGridPointsNotOneCutoffFunction;
	int numGridPointsCutoffFunction;
	int numGridPointsR;
	int numGridPointsQFunctionGrid;
	int numGridPointsExpMinusBetaZeta_iZeta_i;
	int numGridPointsTauFunctionGrid;
	double maxArgumentTauFunctionGrid;
	double maxArgumentQFunctionGrid;
	double maxArgumentExpMinusBetaZeta_iZeta_i;
	double r;
	double temp;
	double temp3;
	double temp4;
	double deltaArgumentR;
	double deltaArgumentCutoffFunction;
	double deltaArgumentQFunctionGrid;
	double deltaArgumentTauFunctionGrid;
	double deltaArgumentExpMinusBetaZeta_iZeta_i;
	double const leftLimitToZero = -DBL_MIN * 1000.0;

	// tauFunctionGrid

	maxArgumentTauFunctionGrid = leadDimInteractionList;

	numGridPointsTauFunctionGrid = (int)
	((maxArgumentTauFunctionGrid) * GRIDDENSITY) + 2;

	r = 0.0;
	deltaArgumentTauFunctionGrid = 1.0 / GRIDDENSITY;

	for (l = 0; l < numGridPointsTauFunctionGrid; l++) {
	tauFunctionGrid[l] = u1 + u2 * u3 * exp(-u4 * r) -
	u2 * exp(-2.0 * u4 * r);
	tauFunctionDerivedGrid[l] = - u2 * u3 * u4 * exp(-u4 * r) +
	2.0 * u2 * u4 * exp(-2.0 * u4 * r);
	r += deltaArgumentTauFunctionGrid;
	}

	// expMinusBetaZeta_iZeta_iGrid

	maxArgumentExpMinusBetaZeta_iZeta_i = leadDimInteractionList;

	numGridPointsExpMinusBetaZeta_iZeta_i = (int)
	((maxArgumentExpMinusBetaZeta_iZeta_i) * GRIDDENSITY) + 2;

	r = 0.0;
	deltaArgumentExpMinusBetaZeta_iZeta_i = 1.0 / GRIDDENSITY;

	for (l = 0; l < numGridPointsExpMinusBetaZeta_iZeta_i; l++) {
	expMinusBetaZeta_iZeta_iGrid[l] = exp(-beta * r * r);
	r += deltaArgumentExpMinusBetaZeta_iZeta_i;
	}

	// qFunctionGrid

	maxArgumentQFunctionGrid = leadDimInteractionList;
	numGridPointsQFunctionGrid =
	(int) ((maxArgumentQFunctionGrid) * GRIDDENSITY) + 2;

	r = 0.0;
	deltaArgumentQFunctionGrid = 1.0 / GRIDDENSITY;

	for (l = 0; l < numGridPointsQFunctionGrid; l++) {
	qFunctionGrid[l] = Q0 * exp(-mu * r);
	r += deltaArgumentQFunctionGrid;
	}

	// cutoffFunction

	numGridPointsOneCutoffFunction =
	(int) ((cutoffC - GRIDSTART) * GRIDDENSITY);
	numGridPointsNotOneCutoffFunction =
	(int) ((cutoffA-cutoffC) * GRIDDENSITY);
	numGridPointsCutoffFunction =
	numGridPointsOneCutoffFunction+numGridPointsNotOneCutoffFunction+2;

	r = GRIDSTART;
	deltaArgumentCutoffFunction = 1.0 / GRIDDENSITY;

	for (l = 0; l < numGridPointsOneCutoffFunction; l++) {
	cutoffFunction[l] = 1.0;
	cutoffFunctionDerived[l] = 0.0;
	r += deltaArgumentCutoffFunction;
	}

	for (l = numGridPointsOneCutoffFunction;
	l < numGridPointsCutoffFunction; l++) {
	temp = (cutoffA - cutoffC)/(r - cutoffC);
	temp3 = temp * temp * temp;
	temp4 = temp3 * temp;
	cutoffFunction[l] = exp(alpha/(1.0-temp3));
	cutoffFunctionDerived[l] = (-3alpha/(cutoffA-cutoffC))
	(temp4/((1-temp3)(1-temp3)))exp(alpha/(1.0-temp3));
	r += deltaArgumentCutoffFunction;
	}

	// pow2B

	numGridPointsR = (int)
	((cutoffA + leftLimitToZero - GRIDSTART) * GRIDDENSITY);

	r = GRIDSTART;
	deltaArgumentR = 1.0 / GRIDDENSITY;
	for (l = 0; l < numGridPointsR; l++) {
	pow2B[l] = pow((B/r),rho);
	exp2B[l] = A * exp(sigma/(r-cutoffA));
	exp3B[l] = exp(gamm/(r-cutoffA));
	r += deltaArgumentR;
	}

	pow2B[numGridPointsR] = pow((B/r),rho);
	exp2B[numGridPointsR]=0;
	exp3B[numGridPointsR]=0;
	r += deltaArgumentR;
	pow2B[numGridPointsR+1] = pow((B/r),rho);
	exp2B[numGridPointsR+1]=0;
	exp3B[numGridPointsR+1]=0;
	}

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

	void PairEDIP::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();

	// 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");

	// allocate tables and internal structures

	allocatePreLoops();
	allocateGrids();
	initGrids();
	}

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

	void PairEDIP::init_style()
	{
	if (force->newton_pair == 0)
	error->all(FLERR,"Pair style EDIP requires newton pair on");

	// need a full neighbor list

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

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

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

	return cutmax;
	}

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

	void PairEDIP::read_file(char *file)
	{
	int params_per_line = 20;
	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 EDIP 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 EDIP 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].A = atof(words[3]);
	params[nparams].B = atof(words[4]);
	params[nparams].cutoffA = atof(words[5]);
	params[nparams].cutoffC = atof(words[6]);
	params[nparams].alpha = atof(words[7]);
	params[nparams].beta = atof(words[8]);
	params[nparams].eta = atof(words[9]);
	params[nparams].gamm = atof(words[10]);
	params[nparams].lambda = atof(words[11]);
	params[nparams].mu = atof(words[12]);
	params[nparams].rho = atof(words[13]);
	params[nparams].sigma = atof(words[14]);
	params[nparams].Q0 = atof(words[15]);
	params[nparams].u1 = atof(words[16]);
	params[nparams].u2 = atof(words[17]);
	params[nparams].u3 = atof(words[18]);
	params[nparams].u4 = atof(words[19]);

	if (params[nparams].A < 0.0 \|\| params[nparams].B < 0.0 \|\|
	params[nparams].cutoffA < 0.0 \|\| params[nparams].cutoffC < 0.0 \|\|
	params[nparams].alpha < 0.0 \|\| params[nparams].beta < 0.0 \|\|
	params[nparams].eta < 0.0 \|\| params[nparams].gamm < 0.0 \|\|
	params[nparams].lambda < 0.0 \|\| params[nparams].mu < 0.0 \|\|
	params[nparams].rho < 0.0 \|\| params[nparams].sigma < 0.0)
	error->all(FLERR,"Illegal EDIP parameter");

	nparams++;
	}

	delete [] words;
	}

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

	void PairEDIP::setup()
	{
	int i,j,k,m,n;
	double rtmp;

	// 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;
	}

	// set cutoff square

	for (m = 0; m < nparams; m++) {
	params[m].cutsq = params[m].cutoffA*params[m].cutoffA;
	}

	// set cutmax to max of all params

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

	// this should be removed for multi species parametrizations

	A = params[0].A;
	B = params[0].B;
	rho = params[0].rho;
	cutoffA = params[0].cutoffA;
	cutoffC = params[0].cutoffC;
	sigma = params[0].sigma;
	lambda = params[0].lambda;
	gamm = params[0].gamm;
	eta = params[0].eta;
	Q0 = params[0].Q0;
	mu = params[0].mu;
	beta = params[0].beta;
	alpha = params[0].alpha;
	u1 = params[0].u1;
	u2 = params[0].u2;
	u3 = params[0].u3;
	u4 = params[0].u4;
	}

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