UniformField.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 "perturbations/UniformField.hpp"
 
#ifdef IS_MPI
#include <mpi.h>
#endif
 
#include "brains/ForceModifier.hpp"
#include "nonbonded/NonBondedInteraction.hpp"
#include "primitives/Molecule.hpp"
#include "types/FixedChargeAdapter.hpp"
#include "types/FluctuatingChargeAdapter.hpp"
#include "types/MultipoleAdapter.hpp"
#include "utils/Constants.hpp"
 
namespace OpenMD {
 
  UniformField::UniformField(SimInfo* info) :
      ForceModifier {info}, initialized {false}, doUniformField {false},
      doParticlePot {false} {
    simParams = info_->getSimParams();
  }
 
  void UniformField::initialize() {
    std::vector<RealType> ef;
 
    if (simParams->haveElectricField()) {
      doUniformField = true;
      ef             = simParams->getElectricField();
    }
    if (simParams->haveUniformField()) {
      doUniformField = true;
      ef             = simParams->getUniformField();
    }
    if (ef.size() != 3) {
      snprintf(painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
               "UniformField: Incorrect number of parameters specified.\n"
               "\tthere should be 3 parameters, but %lu were specified.\n",
               ef.size());
      painCave.isFatal = 1;
      simError();
    }
    EF.x() = ef[0];
    EF.y() = ef[1];
    EF.z() = ef[2];
 
    int storageLayout_ = info_->getSnapshotManager()->getAtomStorageLayout();
    if (storageLayout_ & DataStorage::dslParticlePot) doParticlePot = true;
    initialized = true;
  }
 
  void UniformField::modifyForces() {
    if (!initialized) initialize();
 
    SimInfo::MoleculeIterator i;
    Molecule::AtomIterator j;
    Molecule* mol;
    Atom* atom;
    AtomType* atype;
    potVec longRangePotential(0.0);
 
    RealType C;
    Vector3d D;
    RealType U;
    RealType fPot;
    Vector3d t;
    Vector3d f;
    Vector3d r;
 
    bool isCharge;
 
    if (doUniformField) {
      U    = 0.0;
      fPot = 0.0;
 
      for (mol = info_->beginMolecule(i); mol != NULL;
           mol = info_->nextMolecule(i)) {
        for (atom = mol->beginAtom(j); atom != NULL; atom = mol->nextAtom(j)) {
          isCharge = false;
          C        = 0.0;
 
          atype = atom->getAtomType();
 
          // ad-hoc choice of the origin for potential calculation and
          // fluctuating charge force:
 
          r = atom->getPos();
          info_->getSnapshotManager()->getCurrentSnapshot()->wrapVector(r);
 
          atom->addElectricField(EF * Constants::chargeFieldConvert);
 
          FixedChargeAdapter fca = FixedChargeAdapter(atype);
          if (fca.isFixedCharge()) {
            isCharge = true;
            C        = fca.getCharge();
          }
 
          FluctuatingChargeAdapter fqa = FluctuatingChargeAdapter(atype);
          if (fqa.isFluctuatingCharge()) {
            isCharge = true;
            C += atom->getFlucQPos();
            atom->addFlucQFrc(dot(r, EF) * Constants::chargeFieldConvert);
          }
 
          if (isCharge) {
            f = EF * C * Constants::chargeFieldConvert;
            atom->addFrc(f);
            U = -dot(r, f);
 
            if (doParticlePot) { atom->addParticlePot(U); }
            fPot += U;
          }
 
          MultipoleAdapter ma = MultipoleAdapter(atype);
          if (ma.isDipole()) {
            D = atom->getDipole() * Constants::dipoleFieldConvert;
 
            t = cross(D, EF);
            atom->addTrq(t);
 
            U = -dot(D, EF);
 
            if (doParticlePot) { atom->addParticlePot(U); }
            fPot += U;
          }
        }
      }
 
#ifdef IS_MPI
      MPI_Allreduce(MPI_IN_PLACE, &fPot, 1, MPI_REALTYPE, MPI_SUM,
                    MPI_COMM_WORLD);
#endif
 
      Snapshot* snap     = info_->getSnapshotManager()->getCurrentSnapshot();
      longRangePotential = snap->getLongRangePotentials();
      longRangePotential[ELECTROSTATIC_FAMILY] += fPot;
      snap->setLongRangePotentials(longRangePotential);
    }
  }
}  // namespace OpenMD