Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F80893426
pair_tip4p_long.cpp
No One
Temporary
Actions
Download File
Edit File
Delete File
View Transforms
Subscribe
Mute Notifications
Award Token
Subscribers
None
File Metadata
Details
File Info
Storage
Attached
Created
Tue, Sep 3, 03:09
Size
16 KB
Mime Type
text/x-c
Expires
Thu, Sep 5, 03:09 (2 d)
Engine
blob
Format
Raw Data
Handle
20462988
Attached To
rLAMMPS lammps
pair_tip4p_long.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 authors: Amalie Frischknecht and Ahmed Ismail (SNL)
simpler force assignment added by Rolf Isele-Holder (Aachen University)
------------------------------------------------------------------------- */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pair_tip4p_long.h"
#include "angle.h"
#include "atom.h"
#include "bond.h"
#include "comm.h"
#include "domain.h"
#include "force.h"
#include "kspace.h"
#include "update.h"
#include "respa.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "neigh_request.h"
#include "memory.h"
#include "error.h"
using namespace LAMMPS_NS;
#define EWALD_F 1.12837917
#define EWALD_P 0.3275911
#define A1 0.254829592
#define A2 -0.284496736
#define A3 1.421413741
#define A4 -1.453152027
#define A5 1.061405429
/* ---------------------------------------------------------------------- */
PairTIP4PLong::PairTIP4PLong(LAMMPS *lmp) : PairCoulLong(lmp)
{
tip4pflag = 1;
single_enable = 0;
respa_enable = 0;
nmax = 0;
hneigh = NULL;
newsite = NULL;
// TIP4P cannot compute virial as F dot r
// due to finding bonded H atoms which are not near O atom
no_virial_fdotr_compute = 1;
}
/* ---------------------------------------------------------------------- */
PairTIP4PLong::~PairTIP4PLong()
{
memory->destroy(hneigh);
memory->destroy(newsite);
}
/* ---------------------------------------------------------------------- */
void PairTIP4PLong::compute(int eflag, int vflag)
{
int i,j,ii,jj,inum,jnum,itype,jtype,itable,key;
int n,vlist[6];
int iH1,iH2,jH1,jH2;
double qtmp,xtmp,ytmp,ztmp,delx,dely,delz,ecoul;
double fraction,table;
double r,r2inv,forcecoul,cforce;
double factor_coul;
double grij,expm2,prefactor,t,erfc;
double fO[3],fH[3],fd[3],v[6],xH1[3],xH2[3];
double *x1,*x2;
int *ilist,*jlist,*numneigh,**firstneigh;
double rsq;
ecoul = 0.0;
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
// reallocate hneigh & newsite if necessary
// initialize hneigh[0] to -1 on steps when reneighboring occurred
// initialize hneigh[2] to 0 every step
int nlocal = atom->nlocal;
int nall = nlocal + atom->nghost;
if (atom->nmax > nmax) {
nmax = atom->nmax;
memory->destroy(hneigh);
memory->create(hneigh,nmax,3,"pair:hneigh");
memory->destroy(newsite);
memory->create(newsite,nmax,3,"pair:newsite");
}
if (neighbor->ago == 0)
for (i = 0; i < nall; i++) hneigh[i][0] = -1;
for (i = 0; i < nall; i++) hneigh[i][2] = 0;
double **f = atom->f;
double **x = atom->x;
double *q = atom->q;
tagint *tag = atom->tag;
int *type = atom->type;
double *special_coul = force->special_coul;
double qqrd2e = force->qqrd2e;
double cut_coulsqplus = (cut_coul+2.0*qdist) * (cut_coul+2.0*qdist);
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];
qtmp = q[i];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
itype = type[i];
// if atom I = water O, set x1 = offset charge site
// else x1 = x of atom I
if (itype == typeO) {
if (hneigh[i][0] < 0) {
hneigh[i][0] = iH1 = atom->map(tag[i] + 1);
hneigh[i][1] = iH2 = atom->map(tag[i] + 2);
hneigh[i][2] = 1;
if (iH1 == -1 || iH2 == -1)
error->one(FLERR,"TIP4P hydrogen is missing");
if (atom->type[iH1] != typeH || atom->type[iH2] != typeH)
error->one(FLERR,"TIP4P hydrogen has incorrect atom type");
compute_newsite(x[i],x[iH1],x[iH2],newsite[i]);
} else {
iH1 = hneigh[i][0];
iH2 = hneigh[i][1];
if (hneigh[i][2] == 0) {
hneigh[i][2] = 1;
compute_newsite(x[i],x[iH1],x[iH2],newsite[i]);
}
}
x1 = newsite[i];
} else x1 = x[i];
jlist = firstneigh[i];
jnum = numneigh[i];
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
factor_coul = special_coul[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];
// adjust rsq and delxyz for off-site O charge(s) if necessary
// but only if they are within reach
if (rsq < cut_coulsqplus) {
if (itype == typeO || jtype == typeO) {
// if atom J = water O, set x2 = offset charge site
// else x2 = x of atom J
if (jtype == typeO) {
if (hneigh[j][0] < 0) {
hneigh[j][0] = jH1 = atom->map(tag[j] + 1);
hneigh[j][1] = jH2 = atom->map(tag[j] + 2);
hneigh[j][2] = 1;
if (jH1 == -1 || jH2 == -1)
error->one(FLERR,"TIP4P hydrogen is missing");
if (atom->type[jH1] != typeH || atom->type[jH2] != typeH)
error->one(FLERR,"TIP4P hydrogen has incorrect atom type");
compute_newsite(x[j],x[jH1],x[jH2],newsite[j]);
} else {
jH1 = hneigh[j][0];
jH2 = hneigh[j][1];
if (hneigh[j][2] == 0) {
hneigh[j][2] = 1;
compute_newsite(x[j],x[jH1],x[jH2],newsite[j]);
}
}
x2 = newsite[j];
} else x2 = x[j];
delx = x1[0] - x2[0];
dely = x1[1] - x2[1];
delz = x1[2] - x2[2];
rsq = delx*delx + dely*dely + delz*delz;
}
// Coulombic interaction based on modified rsq
if (rsq < cut_coulsq) {
r2inv = 1 / rsq;
if (!ncoultablebits || rsq <= tabinnersq) {
r = sqrt(rsq);
grij = g_ewald * r;
expm2 = exp(-grij*grij);
t = 1.0 / (1.0 + EWALD_P*grij);
erfc = t * (A1+t*(A2+t*(A3+t*(A4+t*A5)))) * expm2;
prefactor = qqrd2e * qtmp*q[j]/r;
forcecoul = prefactor * (erfc + EWALD_F*grij*expm2);
if (factor_coul < 1.0) {
forcecoul -= (1.0-factor_coul)*prefactor;
}
} else {
union_int_float_t rsq_lookup;
rsq_lookup.f = rsq;
itable = rsq_lookup.i & ncoulmask;
itable >>= ncoulshiftbits;
fraction = (rsq_lookup.f - rtable[itable]) * drtable[itable];
table = ftable[itable] + fraction*dftable[itable];
forcecoul = qtmp*q[j] * table;
if (factor_coul < 1.0) {
table = ctable[itable] + fraction*dctable[itable];
prefactor = qtmp*q[j] * table;
forcecoul -= (1.0-factor_coul)*prefactor;
}
}
cforce = forcecoul * r2inv;
// if i,j are not O atoms, force is applied directly
// if i or j are O atoms, force is on fictitious atom & partitioned
// force partitioning due to Feenstra, J Comp Chem, 20, 786 (1999)
// f_f = fictitious force, fO = f_f (1 - 2 alpha), fH = alpha f_f
// preserves total force and torque on water molecule
// virial = sum(r x F) where each water's atoms are near xi and xj
// vlist stores 2,4,6 atoms whose forces contribute to virial
n = 0;
key = 0;
if (itype != typeO) {
f[i][0] += delx * cforce;
f[i][1] += dely * cforce;
f[i][2] += delz * cforce;
if (vflag) {
v[0] = x[i][0] * delx * cforce;
v[1] = x[i][1] * dely * cforce;
v[2] = x[i][2] * delz * cforce;
v[3] = x[i][0] * dely * cforce;
v[4] = x[i][0] * delz * cforce;
v[5] = x[i][1] * delz * cforce;
}
vlist[n++] = i;
} else {
key++;
fd[0] = delx*cforce;
fd[1] = dely*cforce;
fd[2] = delz*cforce;
fO[0] = fd[0]*(1 - alpha);
fO[1] = fd[1]*(1 - alpha);
fO[2] = fd[2]*(1 - alpha);
fH[0] = 0.5 * alpha * fd[0];
fH[1] = 0.5 * alpha * fd[1];
fH[2] = 0.5 * alpha * fd[2];
f[i][0] += fO[0];
f[i][1] += fO[1];
f[i][2] += fO[2];
f[iH1][0] += fH[0];
f[iH1][1] += fH[1];
f[iH1][2] += fH[2];
f[iH2][0] += fH[0];
f[iH2][1] += fH[1];
f[iH2][2] += fH[2];
if (vflag) {
domain->closest_image(x[i],x[iH1],xH1);
domain->closest_image(x[i],x[iH2],xH2);
v[0] = x[i][0]*fO[0] + xH1[0]*fH[0] + xH2[0]*fH[0];
v[1] = x[i][1]*fO[1] + xH1[1]*fH[1] + xH2[1]*fH[1];
v[2] = x[i][2]*fO[2] + xH1[2]*fH[2] + xH2[2]*fH[2];
v[3] = x[i][0]*fO[1] + xH1[0]*fH[1] + xH2[0]*fH[1];
v[4] = x[i][0]*fO[2] + xH1[0]*fH[2] + xH2[0]*fH[2];
v[5] = x[i][1]*fO[2] + xH1[1]*fH[2] + xH2[1]*fH[2];
}
vlist[n++] = i;
vlist[n++] = iH1;
vlist[n++] = iH2;
}
if (jtype != typeO) {
f[j][0] -= delx * cforce;
f[j][1] -= dely * cforce;
f[j][2] -= delz * cforce;
if (vflag) {
v[0] -= x[j][0] * delx * cforce;
v[1] -= x[j][1] * dely * cforce;
v[2] -= x[j][2] * delz * cforce;
v[3] -= x[j][0] * dely * cforce;
v[4] -= x[j][0] * delz * cforce;
v[5] -= x[j][1] * delz * cforce;
}
vlist[n++] = j;
} else {
key += 2;
fd[0] = -delx*cforce;
fd[1] = -dely*cforce;
fd[2] = -delz*cforce;
fO[0] = fd[0]*(1 - alpha);
fO[1] = fd[1]*(1 - alpha);
fO[2] = fd[2]*(1 - alpha);
fH[0] = 0.5 * alpha * fd[0];
fH[1] = 0.5 * alpha * fd[1];
fH[2] = 0.5 * alpha * fd[2];
f[j][0] += fO[0];
f[j][1] += fO[1];
f[j][2] += fO[2];
f[jH1][0] += fH[0];
f[jH1][1] += fH[1];
f[jH1][2] += fH[2];
f[jH2][0] += fH[0];
f[jH2][1] += fH[1];
f[jH2][2] += fH[2];
if (vflag) {
domain->closest_image(x[j],x[jH1],xH1);
domain->closest_image(x[j],x[jH2],xH2);
v[0] += x[j][0]*fO[0] + xH1[0]*fH[0] + xH2[0]*fH[0];
v[1] += x[j][1]*fO[1] + xH1[1]*fH[1] + xH2[1]*fH[1];
v[2] += x[j][2]*fO[2] + xH1[2]*fH[2] + xH2[2]*fH[2];
v[3] += x[j][0]*fO[1] + xH1[0]*fH[1] + xH2[0]*fH[1];
v[4] += x[j][0]*fO[2] + xH1[0]*fH[2] + xH2[0]*fH[2];
v[5] += x[j][1]*fO[2] + xH1[1]*fH[2] + xH2[1]*fH[2];
}
vlist[n++] = j;
vlist[n++] = jH1;
vlist[n++] = jH2;
}
if (eflag) {
if (!ncoultablebits || rsq <= tabinnersq)
ecoul = prefactor*erfc;
else {
table = etable[itable] + fraction*detable[itable];
ecoul = qtmp*q[j] * table;
}
if (factor_coul < 1.0) ecoul -= (1.0-factor_coul)*prefactor;
} else ecoul = 0.0;
if (evflag) ev_tally_tip4p(key,vlist,v,ecoul,alpha);
}
}
}
}
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairTIP4PLong::settings(int narg, char **arg)
{
if (narg != 6) error->all(FLERR,"Illegal pair_style command");
typeO = force->inumeric(FLERR,arg[0]);
typeH = force->inumeric(FLERR,arg[1]);
typeB = force->inumeric(FLERR,arg[2]);
typeA = force->inumeric(FLERR,arg[3]);
qdist = force->numeric(FLERR,arg[4]);
cut_coul = force->numeric(FLERR,arg[5]);
}
/* ----------------------------------------------------------------------
init specific to this pair style
------------------------------------------------------------------------- */
void PairTIP4PLong::init_style()
{
if (atom->tag_enable == 0)
error->all(FLERR,"Pair style tip4p/long requires atom IDs");
if (!force->newton_pair)
error->all(FLERR,
"Pair style tip4p/long requires newton pair on");
if (!atom->q_flag)
error->all(FLERR,
"Pair style tip4p/long requires atom attribute q");
if (force->bond == NULL)
error->all(FLERR,"Must use a bond style with TIP4P potential");
if (force->angle == NULL)
error->all(FLERR,"Must use an angle style with TIP4P potential");
PairCoulLong::init_style();
// set alpha parameter
double theta = force->angle->equilibrium_angle(typeA);
double blen = force->bond->equilibrium_distance(typeB);
alpha = qdist / (cos(0.5*theta) * blen);
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairTIP4PLong::init_one(int i, int j)
{
return PairCoulLong::init_one(i,j);
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairTIP4PLong::write_restart_settings(FILE *fp)
{
PairCoulLong::write_restart_settings(fp);
fwrite(&typeO,sizeof(int),1,fp);
fwrite(&typeH,sizeof(int),1,fp);
fwrite(&typeB,sizeof(int),1,fp);
fwrite(&typeA,sizeof(int),1,fp);
fwrite(&qdist,sizeof(double),1,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairTIP4PLong::read_restart_settings(FILE *fp)
{
PairCoulLong::read_restart_settings(fp);
if (comm->me == 0) {
fread(&typeO,sizeof(int),1,fp);
fread(&typeH,sizeof(int),1,fp);
fread(&typeB,sizeof(int),1,fp);
fread(&typeA,sizeof(int),1,fp);
fread(&qdist,sizeof(double),1,fp);
}
MPI_Bcast(&typeO,1,MPI_INT,0,world);
MPI_Bcast(&typeH,1,MPI_INT,0,world);
MPI_Bcast(&typeB,1,MPI_INT,0,world);
MPI_Bcast(&typeA,1,MPI_INT,0,world);
MPI_Bcast(&qdist,1,MPI_DOUBLE,0,world);
}
/* ----------------------------------------------------------------------
compute position xM of fictitious charge site for O atom and 2 H atoms
return it as xM
------------------------------------------------------------------------- */
void PairTIP4PLong::compute_newsite(double *xO, double *xH1,
double *xH2, double *xM)
{
double delx1 = xH1[0] - xO[0];
double dely1 = xH1[1] - xO[1];
double delz1 = xH1[2] - xO[2];
domain->minimum_image(delx1,dely1,delz1);
double delx2 = xH2[0] - xO[0];
double dely2 = xH2[1] - xO[1];
double delz2 = xH2[2] - xO[2];
domain->minimum_image(delx2,dely2,delz2);
xM[0] = xO[0] + alpha * 0.5 * (delx1 + delx2);
xM[1] = xO[1] + alpha * 0.5 * (dely1 + dely2);
xM[2] = xO[2] + alpha * 0.5 * (delz1 + delz2);
}
/* ---------------------------------------------------------------------- */
void *PairTIP4PLong::extract(const char *str, int &dim)
{
dim = 0;
if (strcmp(str,"qdist") == 0) return (void *) &qdist;
if (strcmp(str,"typeO") == 0) return (void *) &typeO;
if (strcmp(str,"typeH") == 0) return (void *) &typeH;
if (strcmp(str,"typeA") == 0) return (void *) &typeA;
if (strcmp(str,"typeB") == 0) return (void *) &typeB;
if (strcmp(str,"cut_coul") == 0) return (void *) &cut_coul;
return NULL;
}
/* ----------------------------------------------------------------------
memory usage of hneigh
------------------------------------------------------------------------- */
double PairTIP4PLong::memory_usage()
{
double bytes = maxeatom * sizeof(double);
bytes += maxvatom*6 * sizeof(double);
bytes += 2 * nmax * sizeof(double);
return bytes;
}
Event Timeline
Log In to Comment