RepulsivePower.cpp

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 *
 * SUPPORT OPEN SCIENCE!  If you use OpenMD or its source code in your
 * research, please cite the appropriate papers when you publish your
 * work.  Good starting points are:
 *
 * [1] Meineke, et al., J. Comp. Chem. 26, 252-271 (2005).
 * [2] Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006).
 * [3] Sun, Lin & Gezelter, J. Chem. Phys. 128, 234107 (2008).
 * [4] Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011).
 * [5] Kuang & Gezelter, Mol. Phys., 110, 691-701 (2012).
 * [6] Lamichhane, Gezelter & Newman, J. Chem. Phys. 141, 134109 (2014).
 * [7] Lamichhane, Newman & Gezelter, J. Chem. Phys. 141, 134110 (2014).
 * [8] Bhattarai, Newman & Gezelter, Phys. Rev. B 99, 094106 (2019).
 */
 
#include "nonbonded/RepulsivePower.hpp"
 
#include <cmath>
#include <cstdio>
#include <cstring>
 
#include "types/RepulsivePowerInteractionType.hpp"
#include "utils/simError.h"
 
using namespace std;
 
namespace OpenMD {
 
  RepulsivePower::RepulsivePower() :
      initialized_(false), forceField_(NULL), name_("RepulsivePower") {}
 
  void RepulsivePower::initialize() {
    RPtypes.clear();
    RPtids.clear();
    MixingMap.clear();
    RPtids.resize(forceField_->getNAtomType(), -1);
 
    ForceField::NonBondedInteractionTypeContainer* nbiTypes =
        forceField_->getNonBondedInteractionTypes();
    ForceField::NonBondedInteractionTypeContainer::MapTypeIterator j;
    ForceField::NonBondedInteractionTypeContainer::KeyType keys;
    NonBondedInteractionType* nbt;
    int rptid1, rptid2;
 
    for (nbt = nbiTypes->beginType(j); nbt != NULL;
         nbt = nbiTypes->nextType(j)) {
      if (nbt->isRepulsivePower()) {
        keys          = nbiTypes->getKeys(j);
        AtomType* at1 = forceField_->getAtomType(keys[0]);
        if (at1 == NULL) {
          snprintf(painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
                   "RepulsivePower::initialize could not find AtomType %s\n"
                   "\tto for for %s - %s interaction.\n",
                   keys[0].c_str(), keys[0].c_str(), keys[1].c_str());
          painCave.severity = OPENMD_ERROR;
          painCave.isFatal  = 1;
          simError();
        }
 
        AtomType* at2 = forceField_->getAtomType(keys[1]);
        if (at2 == NULL) {
          snprintf(painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
                   "RepulsivePower::initialize could not find AtomType %s\n"
                   "\tfor %s - %s nonbonded interaction.\n",
                   keys[1].c_str(), keys[0].c_str(), keys[1].c_str());
          painCave.severity = OPENMD_ERROR;
          painCave.isFatal  = 1;
          simError();
        }
 
        int atid1 = at1->getIdent();
        if (RPtids[atid1] == -1) {
          rptid1 = RPtypes.size();
          RPtypes.insert(atid1);
          RPtids[atid1] = rptid1;
        }
        int atid2 = at2->getIdent();
        if (RPtids[atid2] == -1) {
          rptid2 = RPtypes.size();
          RPtypes.insert(atid2);
          RPtids[atid2] = rptid2;
        }
 
        RepulsivePowerInteractionType* rpit =
            dynamic_cast<RepulsivePowerInteractionType*>(nbt);
        if (rpit == NULL) {
          snprintf(
              painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
              "RepulsivePower::initialize could not convert "
              "NonBondedInteractionType\n"
              "\tto RepulsivePowerInteractionType for %s - %s interaction.\n",
              at1->getName().c_str(), at2->getName().c_str());
          painCave.severity = OPENMD_ERROR;
          painCave.isFatal  = 1;
          simError();
        }
 
        RealType sigma   = rpit->getSigma();
        RealType epsilon = rpit->getEpsilon();
        int nRep         = rpit->getNrep();
 
        addExplicitInteraction(at1, at2, sigma, epsilon, nRep);
      }
    }
    initialized_ = true;
  }
 
  void RepulsivePower::addExplicitInteraction(AtomType* atype1,
                                              AtomType* atype2, RealType sigma,
                                              RealType epsilon, int nRep) {
    RPInteractionData mixer;
    mixer.sigma   = sigma;
    mixer.epsilon = epsilon;
    mixer.sigmai  = 1.0 / mixer.sigma;
    mixer.nRep    = nRep;
 
    int nRP   = RPtypes.size();
    int atid1 = atype1->getIdent();
    int atid2 = atype2->getIdent();
    int rptid1, rptid2;
 
    pair<set<int>::iterator, bool> ret;
    ret = RPtypes.insert(atid1);
    if (ret.second == false) {
      // already had this type in the MieMap, just get the mietid:
      rptid1 = RPtids[atid1];
    } else {
      // didn't already have it, so make a new one and assign it:
      rptid1        = nRP;
      RPtids[atid1] = nRP;
      nRP++;
    }
 
    ret = RPtypes.insert(atid2);
    if (ret.second == false) {
      // already had this type in the MieMap, just get the mietid:
      rptid2 = RPtids[atid2];
    } else {
      // didn't already have it, so make a new one and assign it:
      rptid2        = nRP;
      RPtids[atid2] = nRP;
      nRP++;
    }
 
    MixingMap.resize(nRP);
    MixingMap[rptid1].resize(nRP);
 
    MixingMap[rptid1][rptid2] = mixer;
    if (rptid2 != rptid1) {
      MixingMap[rptid2].resize(nRP);
      MixingMap[rptid2][rptid1] = mixer;
    }
  }
 
  void RepulsivePower::calcForce(InteractionData& idat) {
    if (!initialized_) initialize();
 
    RPInteractionData& mixer =
        MixingMap[RPtids[idat.atid1]][RPtids[idat.atid2]];
    RealType sigmai  = mixer.sigmai;
    RealType epsilon = mixer.epsilon;
    int nRep         = mixer.nRep;
 
    RealType ros;
    RealType rcos;
    RealType myPot    = 0.0;
    RealType myPotC   = 0.0;
    RealType myDeriv  = 0.0;
    RealType myDerivC = 0.0;
 
    ros = idat.rij * sigmai;
 
    getNRepulsionFunc(ros, nRep, myPot, myDeriv);
 
    if (idat.shiftedPot) {
      rcos = idat.rcut * sigmai;
      getNRepulsionFunc(rcos, nRep, myPotC, myDerivC);
      myDerivC = 0.0;
    } else if (idat.shiftedForce) {
      rcos = idat.rcut * sigmai;
      getNRepulsionFunc(rcos, nRep, myPotC, myDerivC);
      myPotC = myPotC + myDerivC * (idat.rij - idat.rcut) * sigmai;
    } else {
      myPotC   = 0.0;
      myDerivC = 0.0;
    }
 
    RealType pot_temp = idat.vdwMult * epsilon * (myPot - myPotC);
    idat.vpair += pot_temp;
 
    RealType dudr =
        idat.sw * idat.vdwMult * epsilon * (myDeriv - myDerivC) * sigmai;
 
    idat.pot[VANDERWAALS_FAMILY] += idat.sw * pot_temp;
    if (idat.isSelected) idat.selePot[VANDERWAALS_FAMILY] += idat.sw * pot_temp;
 
    idat.f1 += idat.d * dudr / idat.rij;
 
    return;
  }
 
  void RepulsivePower::getNRepulsionFunc(const RealType& r, int& n,
                                         RealType& pot, RealType& deriv) {
    RealType ri   = 1.0 / r;
    RealType rin  = pow(ri, n);
    RealType rin1 = rin * ri;
 
    pot   = rin;
    deriv = -n * rin1;
 
    return;
  }
 
  RealType RepulsivePower::getSuggestedCutoffRadius(
      pair<AtomType*, AtomType*> atypes) {
    if (!initialized_) initialize();
 
    int atid1  = atypes.first->getIdent();
    int atid2  = atypes.second->getIdent();
    int rptid1 = RPtids[atid1];
    int rptid2 = RPtids[atid2];
 
    if (rptid1 == -1 || rptid2 == -1)
      return 0.0;
    else {
      RPInteractionData mixer = MixingMap[rptid1][rptid2];
      return 2.5 * mixer.sigma;
    }
  }
}  // namespace OpenMD