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pair_cdeam.h
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pair_cdeam.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(eam/cd,PairCDEAM_OneSite)
PairStyle(eam/cd/old,PairCDEAM_TwoSite)
#else
#ifndef LMP_PAIR_CDEAM_H
#define LMP_PAIR_CDEAM_H
#include "pair_eam_alloy.h"
namespace LAMMPS_NS {
class PairCDEAM : public PairEAMAlloy
{
public:
/// Constructor.
PairCDEAM(class LAMMPS*, int cdeamVersion);
/// Destructor.
virtual ~PairCDEAM();
/// Calculates the energies and forces for all atoms in the system.
virtual void compute(int, int);
/// Parses the pair_coeff command parameters for this pair style.
void coeff(int, char **);
/// This is for MPI communication with neighbor nodes.
int pack_forward_comm(int, int *, double *, int, int *);
void unpack_forward_comm(int, int, double *);
int pack_reverse_comm(int, int, double *);
void unpack_reverse_comm(int, int *, double *);
/// Reports the memory usage of this pair style to LAMMPS.
double memory_usage();
void *extract(const char *, int &) { return NULL; }
/// Parses the coefficients of the h polynomial from the end of the EAM file.
void read_h_coeff(char* filename);
public:
// The public interface exposed by this potential class.
// Evaluates the h(x) polynomial for a given local concentration x.
inline double evalH(double x) const {
double v = 0.0;
for(int i = nhcoeff-1; i >= 1; i--) {
v = (v + hcoeff[i]) * x;
}
return v + hcoeff[0];
};
// Calculates the derivative of the h(x) polynomial.
inline double evalHprime(double x) const {
double v = 0.0;
for(int i = nhcoeff-1; i >= 2; i--) {
v = (v + (double)i * hcoeff[i]) * x;
}
return v + hcoeff[1];
};
// We have two versions of the CD-EAM potential. The user can choose which one he wants to use:
//
// Version 1 - One-site concentration: The h(x_i) function depends only on the concentration at the atomic site i.
// This is a new version with a slight modification to the formula. It happens to be computationally more efficient.
// It has been published in the MSMSE 2009 paper.
//
// Version 2 - Two-site concentration: The h(x_ij) function depends on the concentrations at two atomic sites i and j.
// This is the original version from the 2005 PRL paper.
int cdeamVersion;
// Per-atom arrays
// The partial density of B atoms at each atom site.
double *rhoB;
// The intermediate value D_i for each atom.
// The meaning of these values depend on the version of the CD-EAM potential used:
//
// For the one-site concentration version these are the v_i values defined in equation (21)
// of the MSMSE paper.
//
// For the old two-site concentration version these are the M_i values defined in equation (12)
// of the MSMSE paper.
double *D_values;
// The atom type index that is considered to be the A species in the alloy.
int speciesA;
// The atom type index that is considered to be the B species in the alloy.
int speciesB;
protected:
// Evaluation functions:
// This structure specifies an entry in one of the EAM spline tables
// and the corresponding floating point part.
typedef struct {
int m;
double p;
} EAMTableIndex;
// Converts a radius value to an index value to be used in a spline table lookup.
inline EAMTableIndex radiusToTableIndex(double r) const {
EAMTableIndex index;
index.p = r*rdr + 1.0;
index.m = static_cast<int>(index.p);
index.m = index.m <= (nr-1) ? index.m : (nr-1);
index.p -= index.m;
index.p = index.p <= 1.0 ? index.p : 1.0;
return index;
};
// Converts a density value to an index value to be used in a spline table lookup.
inline EAMTableIndex rhoToTableIndex(double rho) const {
EAMTableIndex index;
index.p = rho*rdrho + 1.0;
index.m = static_cast<int>(index.p);
index.m = index.m <= (nrho-1) ? index.m : (nrho-1);
index.p -= index.m;
index.p = index.p <= 1.0 ? index.p : 1.0;
return index;
};
// Computes the derivative of rho(r)
inline double RhoPrimeOfR(const EAMTableIndex& index, int itype, int jtype) const {
const double* coeff = rhor_spline[type2rhor[itype][jtype]][index.m];
return (coeff[0]*index.p + coeff[1])*index.p + coeff[2];
};
// Computes rho(r)
inline double RhoOfR(const EAMTableIndex& index, int itype, int jtype) const {
const double* coeff = rhor_spline[type2rhor[itype][jtype]][index.m];
return ((coeff[3]*index.p + coeff[4])*index.p + coeff[5])*index.p + coeff[6];
};
// Computes the derivative of F(rho)
inline double FPrimeOfRho(const EAMTableIndex& index, int itype) const {
const double* coeff = frho_spline[type2frho[itype]][index.m];
return (coeff[0]*index.p + coeff[1])*index.p + coeff[2];
};
// Computes F(rho)
inline double FofRho(const EAMTableIndex& index, int itype) const {
const double* coeff = frho_spline[type2frho[itype]][index.m];
return ((coeff[3]*index.p + coeff[4])*index.p + coeff[5])*index.p + coeff[6];
};
// Computes the derivative of z2(r)
inline double Z2PrimeOfR(const EAMTableIndex& index, int itype, int jtype) const {
const double* coeff = z2r_spline[type2z2r[itype][jtype]][index.m];
return (coeff[0]*index.p + coeff[1])*index.p + coeff[2];
};
// Computes z2(r)
inline double Z2OfR(const EAMTableIndex& index, int itype, int jtype) const {
const double* coeff = z2r_spline[type2z2r[itype][jtype]][index.m];
return ((coeff[3]*index.p + coeff[4])*index.p + coeff[5])*index.p + coeff[6];
};
// Computes pair potential V_ij(r).
inline double PhiOfR(const EAMTableIndex& index, int itype, int jtype, const double oneOverR) const {
// phi = pair potential energy
// z2 = phi * r
const double* coeff = z2r_spline[type2z2r[itype][jtype]][index.m];
const double z2 = ((coeff[3]*index.p + coeff[4])*index.p + coeff[5])*index.p + coeff[6];
return z2 * oneOverR;
};
// Computes pair potential V_ij(r) and its derivative.
inline double PhiOfR(const EAMTableIndex& index, int itype, int jtype, const double oneOverR, double& phid) const {
// phi = pair potential energy
// phip = phi'
// z2 = phi * r
// z2p = (phi * r)' = (phi' r) + phi
const double* coeff = z2r_spline[type2z2r[itype][jtype]][index.m];
const double z2p = (coeff[0]*index.p + coeff[1])*index.p + coeff[2];
const double z2 = ((coeff[3]*index.p + coeff[4])*index.p + coeff[5])*index.p + coeff[6];
const double phi = z2 * oneOverR;
phid = z2p * oneOverR - phi * oneOverR;
return phi;
};
// Parameters
// h() polynomial function coefficients
double* hcoeff;
// The number of coefficients in the polynomial.
int nhcoeff;
// This specifies the calculation stage to let the pack/unpack communication routines know
// which data to exchange.
int communicationStage;
};
/// The one-site concentration formulation of CD-EAM.
class PairCDEAM_OneSite : public PairCDEAM
{
public:
/// Constructor.
PairCDEAM_OneSite(class LAMMPS* lmp) : PairEAM(lmp), PairCDEAM(lmp, 1) {}
};
/// The two-site concentration formulation of CD-EAM.
class PairCDEAM_TwoSite : public PairCDEAM
{
public:
/// Constructor.
PairCDEAM_TwoSite(class LAMMPS* lmp) : PairEAM(lmp), PairCDEAM(lmp, 2) {}
};
}
#endif
#endif

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