MassDensityZ.cpp

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 *
 * SUPPORT OPEN SCIENCE!  If you use OpenMD or its source code in your
 * research, please cite the following paper when you publish your work:
 *
 * [1] Drisko et al., J. Open Source Softw. 9, 7004 (2024).
 *
 * Good starting points for code and simulation methodology are:
 *
 * [2] Meineke, et al., J. Comp. Chem. 26, 252-271 (2005).
 * [3] Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006).
 * [4] Sun, Lin & Gezelter, J. Chem. Phys. 128, 234107 (2008).
 * [5] Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011).
 * [6] Kuang & Gezelter, Mol. Phys., 110, 691-701 (2012).
 * [7] Lamichhane, Gezelter & Newman, J. Chem. Phys. 141, 134109 (2014).
 * [8] Bhattarai, Newman & Gezelter, Phys. Rev. B 99, 094106 (2019).
 * [9] Drisko & Gezelter, J. Chem. Theory Comput. 20, 4986-4997 (2024).
 */
 
/*
 * Computes the mass density distribution along preferred axis for the
 * selection
 */
 
#include "applications/staticProps/MassDensityZ.hpp"
 
#include <algorithm>
#include <fstream>
 
#include "brains/Thermo.hpp"
#include "io/DumpReader.hpp"
#include "utils/simError.h"
 
namespace OpenMD {
 
  MassDensityZ::MassDensityZ(SimInfo* info, const std::string& filename,
                             const std::string& sele, int nzbins, int axis) :
      StaticAnalyser(info, filename, nzbins),
      selectionScript_(sele), evaluator_(info), seleMan_(info), thermo_(info),
      axis_(axis) {
    evaluator_.loadScriptString(sele);
    if (!evaluator_.isDynamic()) {
      seleMan_.setSelectionSet(evaluator_.evaluate());
    }
 
    massZ_.resize(nBins_);
 
    switch (axis_) {
    case 0:
      axisLabel_ = "x";
      break;
    case 1:
      axisLabel_ = "y";
      break;
    case 2:
    default:
      axisLabel_ = "z";
      break;
    }
 
    setOutputName(getPrefix(filename) + ".MassDensityZ");
  }
 
  void MassDensityZ::process() {
    StuntDouble* sd;
    int ii;
 
    bool usePeriodicBoundaryConditions_ =
        info_->getSimParams()->getUsePeriodicBoundaryConditions();
 
    DumpReader reader(info_, dumpFilename_);
    int nFrames = reader.getNFrames();
    nProcessed_ = nFrames / step_;
 
    for (int istep = 0; istep < nFrames; istep += step_) {
      reader.readFrame(istep);
      currentSnapshot_ = info_->getSnapshotManager()->getCurrentSnapshot();
 
      Mat3x3d hmat = currentSnapshot_->getHmat();
      zBox_.push_back(hmat(axis_, axis_));
 
      RealType halfBoxZ_ = hmat(axis_, axis_) / 2.0;
      RealType area      = 0.0;
      switch (axis_) {
      case 0:
        area = currentSnapshot_->getYZarea();
        break;
      case 1:
        area = currentSnapshot_->getXZarea();
        break;
      case 2:
      default:
        area = currentSnapshot_->getXYarea();
        break;
      }
 
      areas_.push_back(area);
 
      if (evaluator_.isDynamic()) {
        seleMan_.setSelectionSet(evaluator_.evaluate());
      }
 
      for (sd = seleMan_.beginSelected(ii); sd != NULL;
           sd = seleMan_.nextSelected(ii)) {
        Vector3d pos  = sd->getPos();
        RealType mass = sd->getMass();
        if (usePeriodicBoundaryConditions_) currentSnapshot_->wrapVector(pos);
        // shift molecules by half a box to have bins start at 0
        int binNo = int(nBins_ * (halfBoxZ_ + pos[axis_]) / hmat(axis_, axis_));
        massZ_[binNo] += mass;
      }
    }
    writeMassDensityZ();
  }
 
  void MassDensityZ::writeMassDensityZ() {
    // compute average box length:
    std::vector<RealType>::iterator j;
    RealType zSum = 0.0;
    for (j = zBox_.begin(); j != zBox_.end(); ++j) {
      zSum += *j;
    }
    RealType zAve = zSum / zBox_.size();
 
    RealType areaSum = 0.0;
    for (j = areas_.begin(); j != areas_.end(); ++j) {
      areaSum += *j;
    }
    RealType areaAve = areaSum / areas_.size();
 
    std::ofstream rdfStream(outputFilename_.c_str());
    if (rdfStream.is_open()) {
      rdfStream << "#MassDensity(" << axisLabel_ << ")\n";
      rdfStream << "#nFrames:\t" << nProcessed_ << "\n";
      rdfStream << "#selection: (" << selectionScript_ << ")\n";
      rdfStream << "#" << axisLabel_ << "\tdensity (g cm^-3)\n";
      rdfStream.precision(8);  // same precision as the RNEMD files
 
      RealType massDensity;
      for (unsigned int i = 0; i < massZ_.size(); ++i) {
        RealType z = zAve * (i + 0.5) / nBins_;
 
        RealType volSlice = areaAve * zAve / nBins_;
 
        massDensity =
            Constants::densityConvert * massZ_[i] / (volSlice * nProcessed_);
 
        rdfStream << z << "\t" << massDensity << "\n";
      }
 
    } else {
      snprintf(painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
               "MassDensityZ: unable to open %s\n", outputFilename_.c_str());
      painCave.isFatal = 1;
      simError();
    }
 
    rdfStream.close();
  }
}  // namespace OpenMD