InversePowerSeries.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/InversePowerSeries.hpp"
 
#include <cmath>
#include <cstdio>
#include <cstring>
 
#include "types/InversePowerSeriesInteractionType.hpp"
#include "utils/simError.h"
 
using namespace std;
 
namespace OpenMD {
 
  InversePowerSeries::InversePowerSeries() :
      initialized_(false), forceField_(NULL), name_("InversePowerSeries") {}
 
  void InversePowerSeries::initialize() {
    InversePowerSeriesTypes.clear();
    InversePowerSeriesTids.clear();
    MixingMap.clear();
    InversePowerSeriesTids.resize(forceField_->getNAtomType(), -1);
 
    ForceField::NonBondedInteractionTypeContainer* nbiTypes =
        forceField_->getNonBondedInteractionTypes();
    ForceField::NonBondedInteractionTypeContainer::MapTypeIterator j;
    ForceField::NonBondedInteractionTypeContainer::KeyType keys;
    NonBondedInteractionType* nbt;
    int ipstid1, ipstid2;
 
    for (nbt = nbiTypes->beginType(j); nbt != NULL;
         nbt = nbiTypes->nextType(j)) {
      if (nbt->isInversePowerSeries()) {
        keys          = nbiTypes->getKeys(j);
        AtomType* at1 = forceField_->getAtomType(keys[0]);
        if (at1 == NULL) {
          snprintf(painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
                   "InversePowerSeries::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,
                   "InversePowerSeries::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 (InversePowerSeriesTids[atid1] == -1) {
          ipstid1 = InversePowerSeriesTypes.size();
          InversePowerSeriesTypes.insert(atid1);
          InversePowerSeriesTids[atid1] = ipstid1;
        }
        int atid2 = at2->getIdent();
        if (InversePowerSeriesTids[atid2] == -1) {
          ipstid2 = InversePowerSeriesTypes.size();
          InversePowerSeriesTypes.insert(atid2);
          InversePowerSeriesTids[atid2] = ipstid2;
        }
 
        InversePowerSeriesInteractionType* ipsit =
            dynamic_cast<InversePowerSeriesInteractionType*>(nbt);
        if (ipsit == NULL) {
          snprintf(painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
                   "InversePowerSeries::initialize could not convert "
                   "NonBondedInteractionType\n"
                   "\tto InversePowerSeriesInteractionType for %s - %s "
                   "interaction.\n",
                   at1->getName().c_str(), at2->getName().c_str());
          painCave.severity = OPENMD_ERROR;
          painCave.isFatal  = 1;
          simError();
        }
 
        std::vector<int> powers            = ipsit->getPowers();
        std::vector<RealType> coefficients = ipsit->getCoefficients();
 
        addExplicitInteraction(at1, at2, powers, coefficients);
      }
    }
    initialized_ = true;
  }
 
  void InversePowerSeries::addExplicitInteraction(
      AtomType* atype1, AtomType* atype2, std::vector<int> powers,
      std::vector<RealType> coefficients) {
    InversePowerSeriesInteractionData mixer;
    mixer.powers       = powers;
    mixer.coefficients = coefficients;
 
    int ipstid1             = InversePowerSeriesTids[atype1->getIdent()];
    int ipstid2             = InversePowerSeriesTids[atype2->getIdent()];
    int nInversePowerSeries = InversePowerSeriesTypes.size();
 
    MixingMap.resize(nInversePowerSeries);
    MixingMap[ipstid1].resize(nInversePowerSeries);
 
    MixingMap[ipstid1][ipstid2] = mixer;
    if (ipstid2 != ipstid1) {
      MixingMap[ipstid2].resize(nInversePowerSeries);
      MixingMap[ipstid2][ipstid1] = mixer;
    }
  }
 
  void InversePowerSeries::calcForce(InteractionData& idat) {
    if (!initialized_) initialize();
 
    InversePowerSeriesInteractionData& mixer =
        MixingMap[InversePowerSeriesTids[idat.atid1]]
                 [InversePowerSeriesTids[idat.atid2]];
    std::vector<int> powers            = mixer.powers;
    std::vector<RealType> coefficients = mixer.coefficients;
 
    RealType myPot    = 0.0;
    RealType myPotC   = 0.0;
    RealType myDeriv  = 0.0;
    RealType myDerivC = 0.0;
 
    RealType ri  = 1.0 / idat.rij;
    RealType ric = 1.0 / idat.rcut;
 
    RealType fn, fnc;
 
    for (unsigned int i = 0; i < powers.size(); i++) {
      fn  = coefficients[i] * pow(ri, powers[i]);
      fnc = coefficients[i] * pow(ric, powers[i]);
      myPot += fn;
      myPotC += fnc;
      myDeriv -= powers[i] * fn * ri;
      myDerivC -= powers[i] * fnc * ric;
    }
 
    if (idat.shiftedPot) {
      myDerivC = 0.0;
    } else if (idat.shiftedForce) {
      myPotC = myPotC + myDerivC * (idat.rij - idat.rcut);
    } else {
      myPotC   = 0.0;
      myDerivC = 0.0;
    }
 
    RealType pot_temp = idat.vdwMult * (myPot - myPotC);
    idat.vpair += pot_temp;
 
    RealType dudr = idat.sw * idat.vdwMult * (myDeriv - myDerivC);
 
    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;
  }
 
  RealType InversePowerSeries::getSuggestedCutoffRadius(
      pair<AtomType*, AtomType*> atypes) {
    if (!initialized_) initialize();
 
    int atid1   = atypes.first->getIdent();
    int atid2   = atypes.second->getIdent();
    int ipstid1 = InversePowerSeriesTids[atid1];
    int ipstid2 = InversePowerSeriesTids[atid2];
 
    if (ipstid1 == -1 || ipstid2 == -1)
      return 0.0;
    else {
      // This seems to work moderately well as a default.  There's no
      // inherent scale for 1/r^n interactions that we can standardize.
      // 12 angstroms seems to be a reasonably good guess for most
      // cases.
      return 12.0;
    }
  }
}  // namespace OpenMD