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FFSwitch.h
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FFSwitch.h
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/*******************************************************************************
GPU OPTIMIZED MONTE CARLO (GOMC) 2.31
Copyright (C) 2018 GOMC Group
A copy of the GNU General Public License can be found in the COPYRIGHT.txt
along with this program, also can be found at <http://www.gnu.org/licenses/>.
********************************************************************************/
#ifndef FF_SWITCH_H
#define FF_SWITCH_H
#include "EnsemblePreprocessor.h" //For "MIE_INT_ONLY" preprocessor.
#include "FFConst.h" //constants related to particles.
#include "BasicTypes.h" //for uint
#include "NumLib.h" //For Cb, Sq
#include "FFParticle.h"
///////////////////////////////////////////////////////////////////////
////////////////////////// LJ Switch Style ////////////////////////////
///////////////////////////////////////////////////////////////////////
// LJ potential calculation:
// Eij = (cn * eps_ij * ( (sig_ij/rij)^n - (sig_ij/rij)^6)) * FE
// cn = n/(n-6) * ((n/6)^(6/(n-6)))
// FE = 1 , if rij < rswitch
// FE = (rcut^2 - rij^2)^2 *(factor1 + 2 * rij^2)* factor2 , if rcut>rij>rswitch
// factor1 = (rcut^2 - 3 * rswitch^2)
// factor2 = (rcut^2 - rswitch^2)^-3
//
// Virial calculation
// Vir(r) = FE * cn * eps_ij * 6 * ((n/6) * repulse - attract)/rij^2 -
// cn * eps_ij * (repulse - attract) * FW
//
// FW = 0 , if rij < rswitch
// FW = 12 * (rcut^2 - rij^2)(rswitch^2-rij^2) * factor2 , if rcut>rij >rswitch
//
// Eelec = qi * qj * (rij^2/rcut^2 - 1.0)^2 / rij
// Welect = -1 * qi * qj * (dSwitchVal/rij^2 - (rij^2/rcut^2 - 1.0)^2/(rij^3))
// dSwitchVa = 2.0 * (rij^2/rcut^2 - 1.0) * 2.0 * rij/rcut^2
struct FF_SWITCH : public FFParticle {
public:
virtual double CalcEn(const double distSq,
const uint kind1, const uint kind2) const;
virtual double CalcVir(const double distSq,
const uint kind1, const uint kind2) const;
virtual void CalcAdd_1_4(double& en, const double distSq,
const uint kind1, const uint kind2) const;
// coulomb interaction functions
virtual double CalcCoulomb(const double distSq,
const double qi_qj_Fact) const;
virtual double CalcCoulombEn(const double distSq,
const double qi_qj_Fact) const;
virtual double CalcCoulombVir(const double distSq,
const double qi_qj) const;
virtual void CalcCoulombAdd_1_4(double& en, const double distSq,
const double qi_qj_Fact,
const bool NB) const;
//!Returns Ezero, no energy correction
virtual double EnergyLRC(const uint kind1, const uint kind2) const
{
return 0.0;
}
//!!Returns Ezero, no virial correction
virtual double VirialLRC(const uint kind1, const uint kind2) const
{
return 0.0;
}
};
inline void FF_SWITCH::CalcAdd_1_4(double& en, const double distSq,
const uint kind1, const uint kind2) const
{
uint index = FlatIndex(kind1, kind2);
double rCutSq_rijSq = rCutSq - distSq;
double rCutSq_rijSq_Sq = rCutSq_rijSq * rCutSq_rijSq;
double rRat2 = sigmaSq_1_4[index] / distSq;
double rRat4 = rRat2 * rRat2;
double attract = rRat4 * rRat2;
#ifdef MIE_INT_ONLY
uint n_ij = n_1_4[index];
double repulse = num::POW(rRat2, rRat4, attract, n_ij);
#else
double n_ij = n_1_4[index];
double repulse = pow(sqrt(rRat2), n_ij);
#endif
double fE = rCutSq_rijSq_Sq * factor2 * (factor1 + 2 * distSq);
const double factE = ( distSq > rOnSq ? fE : 1.0);
en += (epsilon_cn_1_4[index] * (repulse - attract)) * factE;
}
inline void FF_SWITCH::CalcCoulombAdd_1_4(double& en, const double distSq,
const double qi_qj_Fact,
const bool NB) const
{
double dist = sqrt(distSq);
if(NB)
en += qi_qj_Fact / dist;
else
en += qi_qj_Fact * scaling_14 / dist;
}
//mie potential
inline double FF_SWITCH::CalcEn(const double distSq,
const uint kind1, const uint kind2) const
{
uint index = FlatIndex(kind1, kind2);
double rCutSq_rijSq = rCutSq - distSq;
double rCutSq_rijSq_Sq = rCutSq_rijSq * rCutSq_rijSq;
double rRat2 = sigmaSq[index] / distSq;
double rRat4 = rRat2 * rRat2;
double attract = rRat4 * rRat2;
#ifdef MIE_INT_ONLY
uint n_ij = n[index];
double repulse = num::POW(rRat2, rRat4, attract, n_ij);
#else
double n_ij = n[index];
double repulse = pow(sqrt(rRat2), n_ij);
#endif
double fE = rCutSq_rijSq_Sq * factor2 * (factor1 + 2 * distSq);
const double factE = ( distSq > rOnSq ? fE : 1.0);
return (epsilon_cn[index] * (repulse - attract)) * factE;
}
inline double FF_SWITCH::CalcCoulomb(const double distSq,
const double qi_qj_Fact) const
{
if(ewald) {
double dist = sqrt(distSq);
double val = alpha * dist;
return qi_qj_Fact * erfc(val) / dist;
} else {
double dist = sqrt(distSq);
double switchVal = distSq / rCutSq - 1.0;
switchVal *= switchVal;
return qi_qj_Fact * switchVal / dist;
}
}
//will be used in energy calculation after each move
inline double FF_SWITCH::CalcCoulombEn(const double distSq,
const double qi_qj_Fact) const
{
if(distSq <= rCutLowSq)
return num::BIGNUM;
if(ewald) {
double dist = sqrt(distSq);
double val = alpha * dist;
return qi_qj_Fact * erfc(val) / dist;
} else {
double dist = sqrt(distSq);
double switchVal = distSq / rCutSq - 1.0;
switchVal *= switchVal;
return qi_qj_Fact * switchVal / dist;
}
}
//mie potential
inline double FF_SWITCH::CalcVir(const double distSq,
const uint kind1, const uint kind2) const
{
uint index = FlatIndex(kind1, kind2);
double rCutSq_rijSq = rCutSq - distSq;
double rCutSq_rijSq_Sq = rCutSq_rijSq * rCutSq_rijSq;
double rNeg2 = 1.0 / distSq;
double rRat2 = rNeg2 * sigmaSq[index];
double rRat4 = rRat2 * rRat2;
double attract = rRat4 * rRat2;
#ifdef MIE_INT_ONLY
uint n_ij = n[index];
double repulse = num::POW(rRat2, rRat4, attract, n_ij);
#else
double n_ij = n[index];
double repulse = pow(sqrt(rRat2), n_ij);
#endif
double fE = rCutSq_rijSq_Sq * factor2 * (factor1 + 2 * distSq);
double fW = 12.0 * factor2 * rCutSq_rijSq * (rOnSq - distSq);
const double factE = ( distSq > rOnSq ? fE : 1.0);
const double factW = ( distSq > rOnSq ? fW : 0.0);
double Wij = epsilon_cn_6[index] * (nOver6[index] * repulse - attract) * rNeg2;
double Eij = epsilon_cn[index] * (repulse - attract);
return (Wij * factE - Eij * factW);
}
inline double FF_SWITCH::CalcCoulombVir(const double distSq,
const double qi_qj) const
{
if(ewald) {
double dist = sqrt(distSq);
double constValue = 2.0 * alpha / sqrt(M_PI);
double expConstValue = exp(-1.0 * alpha * alpha * distSq);
double temp = erfc(alpha * dist);
return qi_qj * (temp / dist + constValue * expConstValue) / distSq;
} else {
double dist = sqrt(distSq);
double switchVal = distSq / rCutSq - 1.0;
switchVal *= switchVal;
double dSwitchVal = 2.0 * (distSq / rCutSq - 1.0) * 2.0 * dist / rCutSq;
return -1.0 * qi_qj * (dSwitchVal / distSq - switchVal / (distSq * dist));
}
}
#endif /*FF_SWITCH_H*/