TetrahedralityParamZ.cpp

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 * SUPPORT OPEN SCIENCE!  If you use OpenMD or its source code in your
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 * 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 "applications/staticProps/TetrahedralityParamZ.hpp"
 
#include <algorithm>
#include <fstream>
#include <vector>
 
#include "io/DumpReader.hpp"
#include "primitives/Molecule.hpp"
#include "utils/simError.h"
 
using namespace std;
namespace OpenMD {
  TetrahedralityParamZ::TetrahedralityParamZ(
      SimInfo* info, const std::string& filename, const std::string& sele1,
      const std::string& sele2, double rCut, int nzbins, int axis) :
      StaticAnalyser(info, filename, nzbins),
      selectionScript1_(sele1), selectionScript2_(sele2), seleMan1_(info),
      seleMan2_(info), evaluator1_(info), evaluator2_(info), axis_(axis) {
    evaluator1_.loadScriptString(sele1);
    if (!evaluator1_.isDynamic()) {
      seleMan1_.setSelectionSet(evaluator1_.evaluate());
    }
    evaluator2_.loadScriptString(sele2);
    if (!evaluator2_.isDynamic()) {
      seleMan2_.setSelectionSet(evaluator2_.evaluate());
    }
 
    // Set up cutoff radius:
    rCut_ = rCut;
 
    switch (axis_) {
    case 0:
      axisLabel_ = "x";
      break;
    case 1:
      axisLabel_ = "y";
      break;
    case 2:
    default:
      axisLabel_ = "z";
      break;
    }
 
    // fixed number of bins
    sliceQ_.resize(nBins_);
    sliceCount_.resize(nBins_);
    std::fill(sliceQ_.begin(), sliceQ_.end(), 0.0);
    std::fill(sliceCount_.begin(), sliceCount_.end(), 0);
 
    setOutputName(getPrefix(filename) + ".Qz");
  }
 
  void TetrahedralityParamZ::process() {
    StuntDouble* sd;
    StuntDouble* sd2;
    StuntDouble* sdi;
    StuntDouble* sdj;
    int myIndex;
    Vector3d vec;
    Vector3d ri, rj, rk, rik, rkj;
    RealType r;
    RealType cospsi;
    RealType Qk;
    std::vector<std::pair<RealType, StuntDouble*>> myNeighbors;
    int isd1;
    int isd2;
    bool usePeriodicBoundaryConditions_ =
        info_->getSimParams()->getUsePeriodicBoundaryConditions();
 
    DumpReader reader(info_, dumpFilename_);
    int nFrames = reader.getNFrames();
 
    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;
 
      if (evaluator1_.isDynamic()) {
        seleMan1_.setSelectionSet(evaluator1_.evaluate());
      }
 
      if (evaluator2_.isDynamic()) {
        seleMan2_.setSelectionSet(evaluator2_.evaluate());
      }
 
      // outer loop is over the selected StuntDoubles:
      for (sd = seleMan1_.beginSelected(isd1); sd != NULL;
           sd = seleMan1_.nextSelected(isd1)) {
        myIndex = sd->getGlobalIndex();
 
        Qk = 1.0;
        myNeighbors.clear();
 
        for (sd2 = seleMan2_.beginSelected(isd2); sd2 != NULL;
             sd2 = seleMan2_.nextSelected(isd2)) {
          if (sd2->getGlobalIndex() != myIndex) {
            vec = sd->getPos() - sd2->getPos();
 
            if (usePeriodicBoundaryConditions_)
              currentSnapshot_->wrapVector(vec);
 
            r = vec.length();
 
            // Check to see if neighbor is in bond cutoff
 
            if (r < rCut_) { myNeighbors.push_back(std::make_pair(r, sd2)); }
          }
        }
 
        // Sort the vector using predicate and std::sort
        std::sort(myNeighbors.begin(), myNeighbors.end());
 
        // Use only the 4 closest neighbors to do the rest of the work:
 
        int nbors = myNeighbors.size() > 4 ? 4 : myNeighbors.size();
        int nang  = int(0.5 * (nbors * (nbors - 1)));
 
        rk = sd->getPos();
 
        for (int i = 0; i < nbors - 1; i++) {
          sdi = myNeighbors[i].second;
          ri  = sdi->getPos();
          rik = rk - ri;
          if (usePeriodicBoundaryConditions_) currentSnapshot_->wrapVector(rik);
 
          rik.normalize();
 
          for (int j = i + 1; j < nbors; j++) {
            sdj = myNeighbors[j].second;
            rj  = sdj->getPos();
            rkj = rk - rj;
            if (usePeriodicBoundaryConditions_)
              currentSnapshot_->wrapVector(rkj);
            rkj.normalize();
 
            cospsi = dot(rik, rkj);
 
            // Calculates scaled Qk for each molecule using calculated
            // angles from 4 or fewer nearest neighbors.
            Qk -= (pow(cospsi + 1.0 / 3.0, 2) * 2.25 / nang);
          }
        }
 
        if (nang > 0) {
          if (usePeriodicBoundaryConditions_) currentSnapshot_->wrapVector(rk);
 
          int binNo =
              int(nBins_ * (halfBoxZ_ + rk[axis_]) / hmat(axis_, axis_));
          sliceQ_[binNo] += Qk;
          sliceCount_[binNo] += 1;
        }
      }
    }
    writeQz();
  }
 
  void TetrahedralityParamZ::writeQz() {
    // compute average box length:
 
    RealType zSum = 0.0;
    for (std::vector<RealType>::iterator j = zBox_.begin(); j != zBox_.end();
         ++j) {
      zSum += *j;
    }
    RealType zAve = zSum / zBox_.size();
 
    std::ofstream qZstream(outputFilename_.c_str());
    if (qZstream.is_open()) {
      qZstream << "#Tetrahedrality Parameters (" << axisLabel_ << ")\n";
 
      qZstream << "#nFrames:\t" << zBox_.size() << "\n";
      qZstream << "#selection 1: (" << selectionScript1_ << ")\n";
      qZstream << "#selection 2: (" << selectionScript2_ << ")\n";
      qZstream << "#" << axisLabel_ << "\tQk\n";
      for (unsigned int i = 0; i < sliceQ_.size(); ++i) {
        RealType z = zAve * (i + 0.5) / sliceQ_.size();
        if (sliceCount_[i] != 0) {
          qZstream << z << "\t" << sliceQ_[i] / sliceCount_[i] << "\n";
        }
      }
 
    } else {
      snprintf(painCave.errMsg, MAX_SIM_ERROR_MSG_LENGTH,
               "TetrahedralityParamZ: unable to open %s\n",
               outputFilename_.c_str());
      painCave.isFatal = 1;
      simError();
    }
    qZstream.close();
  }
}  // namespace OpenMD