Homec4science
Diffusion lammps (master) Browse

lammps/src/USER-MESO/pair_mdpd.cpp
f945d4567d4fmaster

Last Change
Raw File

pair_mdpd.cpp
View Options

/* ----------------------------------------------------------------------
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: Zhen Li (Brown University)
Email: zhen_li@brown.edu
------------------------------------------------------------------------- */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "pair_mdpd.h"
#include "atom.h"
#include "atom_vec.h"
#include "comm.h"
#include "update.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "random_mars.h"
#include "citeme.h"
#include "memory.h"
#include "error.h"
#include <time.h>
using namespace LAMMPS_NS;
#define EPSILON 1.0e-10
static const char cite_pair_mdpd[] =
"pair mdpd command:\n\n"
"@Article{ZLi2013_POF,\n"
" author = {Li, Z. and Hu, G.H. and Wang, Z.L. and Ma Y.B. and Zhou, Z.W.},\n"
" title = {Three dimensional flow structures in a moving droplet on substrate: a dissipative particle dynamics study},\n"
" journal = {Physics of Fluids},\n"
" year = {2013},\n"
" volume = {25},\n"
" pages = {072103}\n"
"}\n\n";
/* ---------------------------------------------------------------------- */
PairMDPD::PairMDPD(LAMMPS *lmp) : Pair(lmp)
{
if (lmp->citeme) lmp->citeme->add(cite_pair_mdpd);
writedata = 1;
random = NULL;
}
/* ---------------------------------------------------------------------- */
PairMDPD::~PairMDPD()
{
if (allocated) {
memory->destroy(setflag);
memory->destroy(cutsq);
memory->destroy(cut);
memory->destroy(cut_r);
memory->destroy(A_att);
memory->destroy(B_rep);
memory->destroy(gamma);
memory->destroy(sigma);
}
if (random) delete random;
}
/* ---------------------------------------------------------------------- */
void PairMDPD::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype;
double xtmp,ytmp,ztmp,delx,dely,delz,evdwl,fpair;
double vxtmp,vytmp,vztmp,delvx,delvy,delvz;
double rsq,r,rinv,dot,wc,wc_r, wr,randnum,factor_dpd;
int *ilist,*jlist,*numneigh,**firstneigh;
double rhoi, rhoj;
evdwl = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
double **x = atom->x;
double **v = atom->v;
double **f = atom->f;
double *rho= atom->rho;
int *type = atom->type;
int nlocal = atom->nlocal;
double *special_lj = force->special_lj;
int newton_pair = force->newton_pair;
double dtinvsqrt = 1.0/sqrt(update->dt);
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
// loop over neighbors of my atoms
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
vxtmp = v[i][0];
vytmp = v[i][1];
vztmp = v[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
rhoi = rho[i];
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
factor_dpd = special_lj[sbmask(j)];
j &= NEIGHMASK;
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
jtype = type[j];
if (rsq < cutsq[itype][jtype]) {
r = sqrt(rsq);
if (r < EPSILON) continue; // r can be 0.0 in MDPD systems
rinv = 1.0/r;
delvx = vxtmp - v[j][0];
delvy = vytmp - v[j][1];
delvz = vztmp - v[j][2];
dot = delx*delvx + dely*delvy + delz*delvz;
wc = 1.0 - r/cut[itype][jtype];
wc_r = 1.0 - r/cut_r[itype][jtype];
wc_r = MAX(wc_r,0.0);
wr = wc;
rhoj = rho[j];
randnum = random->gaussian();
// conservative force = A_att * wc + B_rep*(rhoi+rhoj)*wc_r
// drag force = -gamma * wr^2 * (delx dot delv) / r
// random force = sigma * wr * rnd * dtinvsqrt;
fpair = A_att[itype][jtype]*wc + B_rep[itype][jtype]*(rhoi+rhoj)*wc_r;
fpair -= gamma[itype][jtype]*wr*wr*dot*rinv;
fpair += sigma[itype][jtype]*wr*randnum*dtinvsqrt;
fpair *= factor_dpd*rinv;
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) {
// unshifted eng of conservative term:
// eng shifted to 0.0 at cutoff
evdwl = 0.5*A_att[itype][jtype]*cut[itype][jtype] * wr*wr + 0.5*B_rep[itype][jtype]*cut_r[itype][jtype]*(rhoi+rhoj)*wc_r*wc_r;
evdwl *= factor_dpd;
}
if (evflag) ev_tally(i,j,nlocal,newton_pair,evdwl,0.0,fpair,delx,dely,delz);
}
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void PairMDPD::allocate()
{
int i,j;
allocated = 1;
int n = atom->ntypes;
memory->create(setflag,n+1,n+1,"pair:setflag");
for (i = 1; i <= n; i++)
for (j = i; j <= n; j++)
setflag[i][j] = 0;
memory->create(cutsq,n+1,n+1,"pair:cutsq");
memory->create(cut,n+1,n+1,"pair:cut");
memory->create(cut_r,n+1,n+1,"pair:cut_r");
memory->create(A_att,n+1,n+1,"pair:A_att");
memory->create(B_rep,n+1,n+1,"pair:B_rep");
memory->create(gamma,n+1,n+1,"pair:gamma");
memory->create(sigma,n+1,n+1,"pair:sigma");
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairMDPD::settings(int narg, char **arg)
{
if (narg != 3) error->all(FLERR,"Illegal pair_style command");
temperature = force->numeric(FLERR,arg[0]);
cut_global = force->numeric(FLERR,arg[1]);
seed = force->inumeric(FLERR,arg[2]);
// initialize Marsaglia RNG with processor-unique seed
if (seed <= 0 ) {
struct timespec time;
clock_gettime( CLOCK_REALTIME, &time );
seed = time.tv_nsec; // if seed is non-positive, get the current time as the seed
}
delete random;
random = new RanMars(lmp,(seed + comm->me) % 900000000);
// reset cutoffs that have been explicitly set
if (allocated) {
int i,j;
for (i = 1; i <= atom->ntypes; i++)
for (j = i+1; j <= atom->ntypes; j++)
if (setflag[i][j]) cut[i][j] = cut_global;
}
}
/* ----------------------------------------------------------------------
set coeffs for one or more type pairs
------------------------------------------------------------------------- */
void PairMDPD::coeff(int narg, char **arg)
{
if(narg != 7 ) error->all(FLERR,"Incorrect args for pair coefficients\n itype jtype A B gamma cutA cutB");
if (!allocated) allocate();
int ilo,ihi,jlo,jhi;
force->bounds(FLERR,arg[0],atom->ntypes,ilo,ihi);
force->bounds(FLERR,arg[1],atom->ntypes,jlo,jhi);
double A_one = force->numeric(FLERR,arg[2]);
double B_one = force->numeric(FLERR,arg[3]);
double gamma_one = force->numeric(FLERR,arg[4]);
double cut_one = force->numeric(FLERR,arg[5]);
double cut_two = force->numeric(FLERR,arg[6]);
if(cut_one < cut_two) error->all(FLERR,"Incorrect args for pair coefficients\n cutA should be larger than cutB.");
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
A_att[i][j] = A_one;
B_rep[i][j] = B_one;
gamma[i][j] = gamma_one;
cut[i][j] = cut_one;
cut_r[i][j] = cut_two;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args for pair coefficients");
}
/* ----------------------------------------------------------------------
init specific to this pair style
------------------------------------------------------------------------- */
void PairMDPD::init_style()
{
if (comm->ghost_velocity == 0)
error->all(FLERR,"Pair mdpd requires ghost atoms store velocity");
// if newton off, forces between atoms ij will be double computed
// using different random numbers
if (force->newton_pair == 0 && comm->me == 0) error->warning(FLERR,
"Pair mdpd needs newton pair on for momentum conservation");
neighbor->request(this,instance_me);
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairMDPD::init_one(int i, int j)
{
if (setflag[i][j] == 0) error->all(FLERR,"All pair coeffs are not set");
sigma[i][j] = sqrt(2.0*force->boltz*temperature*gamma[i][j]);
cut[j][i] = cut[i][j];
cut_r[j][i] = cut_r[i][j];
A_att[j][i] = A_att[i][j];
B_rep[j][i] = B_rep[i][j];
gamma[j][i] = gamma[i][j];
sigma[j][i] = sigma[i][j];
return cut[i][j];
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairMDPD::write_restart(FILE *fp)
{
write_restart_settings(fp);
int i,j;
for (i = 1; i <= atom->ntypes; i++)
for (j = i; j <= atom->ntypes; j++) {
fwrite(&setflag[i][j],sizeof(int),1,fp);
if (setflag[i][j]) {
fwrite(&A_att[i][j],sizeof(double),1,fp);
fwrite(&B_rep[i][j],sizeof(double),1,fp);
fwrite(&gamma[i][j],sizeof(double),1,fp);
fwrite(&cut[i][j],sizeof(double),1,fp);
fwrite(&cut_r[i][j],sizeof(double),1,fp);
}
}
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairMDPD::read_restart(FILE *fp)
{
read_restart_settings(fp);
allocate();
int i,j;
int me = comm->me;
for (i = 1; i <= atom->ntypes; i++)
for (j = i; j <= atom->ntypes; j++) {
if (me == 0) fread(&setflag[i][j],sizeof(int),1,fp);
MPI_Bcast(&setflag[i][j],1,MPI_INT,0,world);
if (setflag[i][j]) {
if (me == 0) {
fread(&A_att[i][j],sizeof(double),1,fp);
fread(&B_rep[i][j],sizeof(double),1,fp);
fread(&gamma[i][j],sizeof(double),1,fp);
fread(&cut[i][j],sizeof(double),1,fp);
fread(&cut_r[i][j],sizeof(double),1,fp);
}
MPI_Bcast(&A_att[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&B_rep[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&gamma[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut[i][j],1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut_r[i][j],1,MPI_DOUBLE,0,world);
}
}
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairMDPD::write_restart_settings(FILE *fp)
{
fwrite(&temperature,sizeof(double),1,fp);
fwrite(&cut_global,sizeof(double),1,fp);
fwrite(&seed,sizeof(int),1,fp);
fwrite(&mix_flag,sizeof(int),1,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairMDPD::read_restart_settings(FILE *fp)
{
if (comm->me == 0) {
fread(&temperature,sizeof(double),1,fp);
fread(&cut_global,sizeof(double),1,fp);
fread(&seed,sizeof(int),1,fp);
fread(&mix_flag,sizeof(int),1,fp);
}
MPI_Bcast(&temperature,1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut_global,1,MPI_DOUBLE,0,world);
MPI_Bcast(&seed,1,MPI_INT,0,world);
MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
// initialize Marsaglia RNG with processor-unique seed
// same seed that pair_style command initially specified
if (random) delete random;
random = new RanMars(lmp,seed + comm->me);
}
/* ----------------------------------------------------------------------
proc 0 writes to data file
------------------------------------------------------------------------- */
void PairMDPD::write_data(FILE *fp)
{
for (int i = 1; i <= atom->ntypes; i++)
fprintf(fp,"%d %g %g %g\n",i,A_att[i][i],B_rep[i][i],gamma[i][i]);
}
/* ----------------------------------------------------------------------
proc 0 writes all pairs to data file
------------------------------------------------------------------------- */
void PairMDPD::write_data_all(FILE *fp)
{
for (int i = 1; i <= atom->ntypes; i++)
for (int j = i; j <= atom->ntypes; j++)
fprintf(fp,"%d %d %g %g %g %g %g\n",i,j,A_att[i][j],B_rep[i][j],gamma[i][j],cut[i][j],cut_r[i][j]);
}
c4science · Help