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lammps/src/USER-CD-EAM/pair_cdeam.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: Alexander Stukowski (stukowski at mm.tu-darmstadt.de)
------------------------------------------------------------------------- */
/*
Concentration-dependent EAM (CD-EAM) potential for multi-component
systems.
This potential class implements an improved version of the original
CD-EAM formalism. The new version (a.k.a. one-site model;
cdeamVersion==1) has been published in
A. Stukowski, B. Sadigh, P. Erhart and A. Caro
Efficient implementation of the concentration-dependent embedded
atom method for molecular-dynamics and Monte-Carlo simulations
Model. Simul. Mater. Sci. Eng., 2009, 075005
This new formulation is more efficient for MD and Monte-Carlo
simulations and is the default.
The original formulation (a.k.a. two-site model; cdeamVersion==2) is
also implemented and has been published in
A. Caro, D. A. Crowson and M. Caro
Classical Many-Body Potential for Concentrated Alloys and the
Inversion of Order in Iron-Chromium Alloys
Phys. Rev. Lett., APS, 2005, 95, 075702
*/
#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "pair_cdeam.h"
#include "atom.h"
#include "force.h"
#include "comm.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
//using namespace std;
// This is for debugging purposes. The ASSERT() macro is used in the code to check
// if everything runs as expected. Change this to #if 0 if you don't need the checking.
#if 0
#define ASSERT(cond) ((!(cond)) ? my_failure(error,__FILE__,__LINE__) : my_noop())
inline void my_noop() {}
inline void my_failure(Error* error, const char* file, int line) {
char str[1024];
sprintf(str,"Assertion failure: File %s, line %i", file, line);
error->one(str);
}
#else
#define ASSERT(cond)
#endif
#define MAXLINE 1024 // This sets the maximum line length in EAM input files.
PairCDEAM::PairCDEAM(LAMMPS *lmp, int _cdeamVersion) : PairEAM(lmp), PairEAMAlloy(lmp), cdeamVersion(_cdeamVersion)
{
single_enable = 0;
rhoB = NULL;
D_values = NULL;
hcoeff = NULL;
// Set communication buffer sizes needed by this pair style.
if(cdeamVersion == 1) {
comm_forward = 4;
comm_reverse = 3;
}
else if(cdeamVersion == 2) {
comm_forward = 3;
comm_reverse = 2;
}
else {
error->all("Invalid CD-EAM potential version.");
}
}
PairCDEAM::~PairCDEAM()
{
memory->sfree(rhoB);
memory->sfree(D_values);
if(hcoeff) delete[] hcoeff;
}
void PairCDEAM::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype;
double xtmp,ytmp,ztmp,delx,dely,delz,evdwl,fpair;
double rsq,rhoip,rhojp,recip,phi;
int *ilist,*jlist,*numneigh,**firstneigh;
evdwl = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
// Grow per-atom arrays if necessary
if(atom->nmax > nmax) {
memory->sfree(rho);
memory->sfree(fp);
memory->sfree(rhoB);
memory->sfree(D_values);
nmax = atom->nmax;
rho = (double *)memory->smalloc(nmax*sizeof(double),"pair:rho");
rhoB = (double *)memory->smalloc(nmax*sizeof(double),"pair:rhoB");
fp = (double *)memory->smalloc(nmax*sizeof(double),"pair:fp");
D_values = (double *)memory->smalloc(nmax*sizeof(double),"pair:D_values");
}
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;
// Zero out per-atom arrays.
int m = nlocal + atom->nghost;
for(i = 0; i < m; i++) {
rho[i] = 0.0;
rhoB[i] = 0.0;
D_values[i] = 0.0;
}
// Stage I
// Compute rho and rhoB at each local atom site.
// Additionally calculate the D_i values here if we are using the one-site formulation.
// For the two-site formulation we have to calculate the D values in an extra loop (Stage II).
for(ii = 0; ii < inum; ii++) {
i = ilist[ii];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
for(jj = 0; jj < jnum; jj++) {
j = jlist[jj];
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
if(rsq < cutforcesq) {
jtype = type[j];
double r = sqrt(rsq);
const EAMTableIndex index = radiusToTableIndex(r);
double localrho = RhoOfR(index, jtype, itype);
rho[i] += localrho;
if(jtype == speciesB) rhoB[i] += localrho;
if(newton_pair || j < nlocal) {
localrho = RhoOfR(index, itype, jtype);
rho[j] += localrho;
if(itype == speciesB) rhoB[j] += localrho;
}
if(cdeamVersion == 1 && itype != jtype) {
// Note: if the i-j interaction is not concentration dependent (because either
// i or j are not species A or B) then its contribution to D_i and D_j should
// be ignored.
// This if-clause is only required for a ternary.
if((itype == speciesA && jtype == speciesB) || (jtype == speciesA && itype == speciesB)) {
double Phi_AB = PhiOfR(index, itype, jtype, 1.0 / r);
D_values[i] += Phi_AB;
if(newton_pair || j < nlocal)
D_values[j] += Phi_AB;
}
}
}
}
}
// Communicate and sum densities.
if(newton_pair) {
communicationStage = 1;
comm->reverse_comm_pair(this);
}
// fp = derivative of embedding energy at each atom
// phi = embedding energy at each atom
for(ii = 0; ii < inum; ii++) {
i = ilist[ii];
EAMTableIndex index = rhoToTableIndex(rho[i]);
fp[i] = FPrimeOfRho(index, type[i]);
if(eflag) {
phi = FofRho(index, type[i]);
if(eflag_global) eng_vdwl += phi;
if(eflag_atom) eatom[i] += phi;
}
}
// Communicate derivative of embedding function and densities
// and D_values (this for one-site formulation only).
communicationStage = 2;
comm->comm_pair(this);
// The electron densities may not drop to zero because then the concentration would no longer be defined.
// But the concentration is not needed anyway if there is no interaction with another atom, which is the case
// if the electron density is exactly zero. That's why the following lines have been commented out.
//
//for(i = 0; i < nlocal + atom->nghost; i++) {
// if(rho[i] == 0 && (type[i] == speciesA || type[i] == speciesB))
// error->one("CD-EAM potential routine: Detected atom with zero electron density.");
//}
// Stage II
// This is only required for the original two-site formulation of the CD-EAM potential.
if(cdeamVersion == 2) {
// Compute intermediate value D_i for each atom.
for(ii = 0; ii < inum; ii++) {
i = ilist[ii];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
// This code line is required for ternary alloys.
if(itype != speciesA && itype != speciesB) continue;
double x_i = rhoB[i] / rho[i]; // Concentration at atom i.
for(jj = 0; jj < jnum; jj++) {
j = jlist[jj];
jtype = type[j];
if(itype == jtype) continue;
// This code line is required for ternary alloys.
if(jtype != speciesA && jtype != speciesB) continue;
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
if(rsq < cutforcesq) {
double r = sqrt(rsq);
const EAMTableIndex index = radiusToTableIndex(r);
// The concentration independent part of the cross pair potential.
double Phi_AB = PhiOfR(index, itype, jtype, 1.0 / r);
// Average concentration of two sites
double x_ij = 0.5 * (x_i + rhoB[j]/rho[j]);
// Calculate derivative of h(x_ij) polynomial function.
double h_prime = evalHprime(x_ij);
D_values[i] += h_prime * Phi_AB / (2.0 * rho[i] * rho[i]);
if(newton_pair || j < nlocal)
D_values[j] += h_prime * Phi_AB / (2.0 * rho[j] * rho[j]);
}
}
}
// Communicate and sum D values.
if(newton_pair) {
communicationStage = 3;
comm->reverse_comm_pair(this);
}
communicationStage = 4;
comm->comm_pair(this);
}
// Stage III
// Compute force acting on each atom.
for(ii = 0; ii < inum; ii++) {
i = ilist[ii];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
// Concentration at site i
double x_i = -1.0; // The value -1 indicates: no concentration dependence for all interactions of atom i.
// It will be replaced by the concentration at site i if atom i is either A or B.
double D_i, h_prime_i;
// This if-clause is only required for ternary alloys.
if((itype == speciesA || itype == speciesB) && rho[i] != 0.0) {
// Compute local concentration at site i.
x_i = rhoB[i]/rho[i];
ASSERT(x_i >= 0 && x_i<=1.0);
if(cdeamVersion == 1) {
// Calculate derivative of h(x_i) polynomial function.
h_prime_i = evalHprime(x_i);
D_i = D_values[i] * h_prime_i / (2.0 * rho[i] * rho[i]);
}
else if(cdeamVersion == 2) {
D_i = D_values[i];
}
else ASSERT(false);
}
for(jj = 0; jj < jnum; jj++) {
j = jlist[jj];
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
if(rsq < cutforcesq) {
jtype = type[j];
double r = sqrt(rsq);
const EAMTableIndex index = radiusToTableIndex(r);
// rhoip = derivative of (density at atom j due to atom i)
// rhojp = derivative of (density at atom i due to atom j)
// psip needs both fp[i] and fp[j] terms since r_ij appears in two
// terms of embed eng: Fi(sum rho_ij) and Fj(sum rho_ji)
// hence embed' = Fi(sum rho_ij) rhojp + Fj(sum rho_ji) rhoip
rhoip = RhoPrimeOfR(index, itype, jtype);
rhojp = RhoPrimeOfR(index, jtype, itype);
fpair = fp[i]*rhojp + fp[j]*rhoip;
recip = 1.0/r;
double x_j = -1; // The value -1 indicates: no concentration dependence for this i-j pair
// because atom j is not of species A nor B.
// This code line is required for ternary alloy.
if(jtype == speciesA || jtype == speciesB) {
ASSERT(rho[i] != 0.0);
ASSERT(rho[j] != 0.0);
// Compute local concentration at site j.
x_j = rhoB[j]/rho[j];
ASSERT(x_j >= 0 && x_j<=1.0);
double D_j;
if(cdeamVersion == 1) {
// Calculate derivative of h(x_j) polynomial function.
double h_prime_j = evalHprime(x_j);
D_j = D_values[j] * h_prime_j / (2.0 * rho[j] * rho[j]);
}
else if(cdeamVersion == 2) {
D_j = D_values[j];
}
else ASSERT(false);
double t2 = -rhoB[j];
if(itype == speciesB) t2 += rho[j];
fpair += D_j * rhoip * t2;
}
// This if-clause is only required for a ternary alloy.
// Actually we don't need it at all because D_i should be zero anyway if
// atom i has no concentration dependent interactions (because it is not species A or B).
if(x_i != -1.0) {
double t1 = -rhoB[i];
if(jtype == speciesB) t1 += rho[i];
fpair += D_i * rhojp * t1;
}
double phip;
double phi = PhiOfR(index, itype, jtype, recip, phip);
if(itype == jtype || x_i == -1.0 || x_j == -1.0) {
// Case of no concentration dependence.
fpair += phip;
}
else {
// We have a concentration dependence for the i-j interaction.
double h;
if(cdeamVersion == 1) {
// Calculate h(x_i) polynomial function.
double h_i = evalH(x_i);
// Calculate h(x_j) polynomial function.
double h_j = evalH(x_j);
h = 0.5 * (h_i + h_j);
}
else if(cdeamVersion == 2) {
// Average concentration.
double x_ij = 0.5 * (x_i + x_j);
// Calculate h(x_ij) polynomial function.
h = evalH(x_ij);
}
else ASSERT(false);
fpair += h * phip;
phi *= h;
}
// Divide by r_ij and negate to get forces from gradient.
fpair /= -r;
f[i][0] += delx*fpair;
f[i][1] += dely*fpair;
f[i][2] += delz*fpair;
if(newton_pair || j < nlocal) {
f[j][0] -= delx*fpair;
f[j][1] -= dely*fpair;
f[j][2] -= delz*fpair;
}
if(eflag) evdwl = phi;
if(evflag) ev_tally(i,j,nlocal,newton_pair,evdwl,0.0,fpair,delx,dely,delz);
}
}
}
if(vflag_fdotr) virial_compute();
}
/* ---------------------------------------------------------------------- */
void PairCDEAM::coeff(int narg, char **arg)
{
PairEAMAlloy::coeff(narg, arg);
// Make sure the EAM file is a CD-EAM binary alloy.
if(setfl->nelements < 2)
error->all("The EAM file must contain at least 2 elements to be used with the eam/cd pair style.");
// Read in the coefficients of the h polynomial from the end of the EAM file.
read_h_coeff(arg[2]);
// Determine which atom type is the A species and which is the B species in the alloy.
// By default take the first element (index 0) in the EAM file as the A species
// and the second element (index 1) in the EAM file as the B species.
speciesA = -1;
speciesB = -1;
for(int i = 1; i <= atom->ntypes; i++) {
if(map[i] == 0) {
if(speciesA >= 0)
error->all("The first element from the EAM file may only be mapped to a single atom type.");
speciesA = i;
}
if(map[i] == 1) {
if(speciesB >= 0)
error->all("The second element from the EAM file may only be mapped to a single atom type.");
speciesB = i;
}
}
if(speciesA < 0)
error->all("The first element from the EAM file must be mapped to exactly one atom type.");
if(speciesB < 0)
error->all("The second element from the EAM file must be mapped to exactly one atom type.");
}
/* ----------------------------------------------------------------------
Reads in the h(x) polynomial coefficients
------------------------------------------------------------------------- */
void PairCDEAM::read_h_coeff(char *filename)
{
if(comm->me == 0) {
// Open potential file
FILE *fp;
char line[MAXLINE];
char nextline[MAXLINE];
fp = fopen(filename,"r");
if (fp == NULL) {
char str[128];
sprintf(str,"Cannot open EAM potential file %s", filename);
error->one(str);
}
// h coefficients are stored at the end of the file.
// Skip to last line of file.
while(fgets(nextline, MAXLINE, fp) != NULL) {
strcpy(line, nextline);
}
char* ptr = strtok(line, " \t\n\r\f");
int degree = atoi(ptr);
nhcoeff = degree+1;
hcoeff = new double[nhcoeff];
int i = 0;
while((ptr = strtok(NULL," \t\n\r\f")) != NULL && i < nhcoeff) {
hcoeff[i++] = atof(ptr);
}
if(i != nhcoeff || nhcoeff < 1)
error->one("Failed to read h(x) function coefficients from EAM file.");
// Close the potential file.
fclose(fp);
}
MPI_Bcast(&nhcoeff, 1, MPI_INT, 0, world);
if(comm->me != 0) hcoeff = new double[nhcoeff];
MPI_Bcast(hcoeff, nhcoeff, MPI_DOUBLE, 0, world);
}
/* ---------------------------------------------------------------------- */
int PairCDEAM::pack_comm(int n, int *list, double *buf, int pbc_flag, int *pbc)
{
int i,j,m;
m = 0;
if(communicationStage == 2) {
if(cdeamVersion == 1) {
for (i = 0; i < n; i++) {
j = list[i];
buf[m++] = fp[j];
buf[m++] = rho[j];
buf[m++] = rhoB[j];
buf[m++] = D_values[j];
}
return 4;
}
else if(cdeamVersion == 2) {
for (i = 0; i < n; i++) {
j = list[i];
buf[m++] = fp[j];
buf[m++] = rho[j];
buf[m++] = rhoB[j];
}
return 3;
}
else { ASSERT(false); return 0; }
}
else if(communicationStage == 4) {
for (i = 0; i < n; i++) {
j = list[i];
buf[m++] = D_values[j];
}
return 1;
}
else return 0;
}
/* ---------------------------------------------------------------------- */
void PairCDEAM::unpack_comm(int n, int first, double *buf)
{
int i,m,last;
m = 0;
last = first + n;
if(communicationStage == 2) {
if(cdeamVersion == 1) {
for(i = first; i < last; i++) {
fp[i] = buf[m++];
rho[i] = buf[m++];
rhoB[i] = buf[m++];
D_values[i] = buf[m++];
}
}
else if(cdeamVersion == 2) {
for(i = first; i < last; i++) {
fp[i] = buf[m++];
rho[i] = buf[m++];
rhoB[i] = buf[m++];
}
}
else ASSERT(false);
}
else if(communicationStage == 4) {
for(i = first; i < last; i++) {
D_values[i] = buf[m++];
}
}
}
/* ---------------------------------------------------------------------- */
int PairCDEAM::pack_reverse_comm(int n, int first, double *buf)
{
int i,m,last;
m = 0;
last = first + n;
if(communicationStage == 1) {
if(cdeamVersion == 1) {
for(i = first; i < last; i++) {
buf[m++] = rho[i];
buf[m++] = rhoB[i];
buf[m++] = D_values[i];
}
return 3;
}
else if(cdeamVersion == 2) {
for(i = first; i < last; i++) {
buf[m++] = rho[i];
buf[m++] = rhoB[i];
}
return 2;
}
else { ASSERT(false); return 0; }
}
else if(communicationStage == 3) {
for(i = first; i < last; i++) {
buf[m++] = D_values[i];
}
return 1;
}
else return 0;
}
/* ---------------------------------------------------------------------- */
void PairCDEAM::unpack_reverse_comm(int n, int *list, double *buf)
{
int i,j,m;
m = 0;
if(communicationStage == 1) {
if(cdeamVersion == 1) {
for(i = 0; i < n; i++) {
j = list[i];
rho[j] += buf[m++];
rhoB[j] += buf[m++];
D_values[j] += buf[m++];
}
}
else if(cdeamVersion == 2) {
for(i = 0; i < n; i++) {
j = list[i];
rho[j] += buf[m++];
rhoB[j] += buf[m++];
}
}
else ASSERT(false);
}
else if(communicationStage == 3) {
for(i = 0; i < n; i++) {
j = list[i];
D_values[j] += buf[m++];
}
}
}
/* ----------------------------------------------------------------------
memory usage of local atom-based arrays
------------------------------------------------------------------------- */
double PairCDEAM::memory_usage()
{
double bytes = 2 * nmax * sizeof(double);
return PairEAMAlloy::memory_usage() + bytes;
}
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