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pair_sw_omp.h
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Fri, Aug 16, 22:20

pair_sw_omp.h
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/* -*- c++ -*- -----------------------------------------------------------
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.
------------------------------------------------------------------------- */
#ifdef PAIR_CLASS
PairStyle(sw/omp,PairSWOMP)
#else
#ifndef LMP_PAIR_SW_OMP_H
#define LMP_PAIR_SW_OMP_H
#include "pair_omp.h"
namespace LAMMPS_NS {
class PairSWOMP : public PairOMP {
public:
PairSWOMP(class LAMMPS *);
~PairSWOMP();
virtual void compute(int, int);
virtual void settings(int, char **);
virtual void coeff(int, char **);
virtual double init_one(int, int);
virtual void init_style();
protected:
struct Param {
double epsilon,sigma;
double littlea,lambda,gamma,costheta;
double biga,bigb;
double powerp,powerq;
double tol;
double cut,cutsq;
double sigma_gamma,lambda_epsilon,lambda_epsilon2;
double c1,c2,c3,c4,c5,c6;
int ielement,jelement,kelement;
};
double cutmax; // max cutoff for all elements
int nelements; // # of unique elements
char **elements; // names of unique elements
int ***elem2param; // mapping from element triplets to parameters
int *map; // mapping from atom types to elements
int nparams; // # of stored parameter sets
int maxparam; // max # of parameter sets
Param *params; // parameter set for an I-J-K interaction
protected:
void allocate();
void read_file(char *);
void setup();
template <int EVFLAG, int EFLAG, int NEWTON_PAIR> void eval();
/* ---------------------------------------------------------------------- */
template <int EFLAG>
void twobody(const Param *param, const double rsq, double &fforce, double &eng)
{
double r,rinvsq,rp,rq,rainv,rainvsq,expsrainv;
r = sqrt(rsq);
rinvsq = 1.0/rsq;
rp = pow(r,-param->powerp);
rq = pow(r,-param->powerq);
rainv = 1.0 / (r - param->cut);
rainvsq = rainv*rainv*r;
expsrainv = exp(param->sigma * rainv);
fforce = (param->c1*rp - param->c2*rq +
(param->c3*rp -param->c4*rq) * rainvsq) * expsrainv * rinvsq;
if (EFLAG) eng = (param->c5*rp - param->c6*rq) * expsrainv;
};
/* ---------------------------------------------------------------------- */
template <int EFLAG>
void threebody(const Param *paramij, const Param *paramik, const Param *paramijk,
const double rsq1, const double rsq2,
double *delr1, double *delr2,
double *fj, double *fk, 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;
double facang,facang12,csfacang,csfac1,csfac2;
r1 = sqrt(rsq1);
rinvsq1 = 1.0/rsq1;
rainv1 = 1.0/(r1 - paramij->cut);
gsrainv1 = paramij->sigma_gamma * rainv1;
gsrainvsq1 = gsrainv1*rainv1/r1;
expgsrainv1 = exp(gsrainv1);
r2 = sqrt(rsq2);
rinvsq2 = 1.0/rsq2;
rainv2 = 1.0/(r2 - paramik->cut);
gsrainv2 = paramik->sigma_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;
facexp = expgsrainv1*expgsrainv2;
// facrad = sqrt(paramij->lambda_epsilon*paramik->lambda_epsilon) *
// facexp*delcssq;
facrad = paramijk->lambda_epsilon * facexp*delcssq;
frad1 = facrad*gsrainvsq1;
frad2 = facrad*gsrainvsq2;
facang = paramijk->lambda_epsilon2 * facexp*delcs;
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;
};
};
}
#endif
#endif

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