Bend.hpp

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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).
 */
 
/**
 * @file Bend.hpp
 * @author    tlin
 * @date  11/01/2004
 * @version 1.0
 */
 
#ifndef PRIMITIVES_BEND_HPP
#define PRIMITIVES_BEND_HPP
 
#include "primitives/Atom.hpp"
#include "primitives/ShortRangeInteraction.hpp"
#include "types/BendType.hpp"
 
namespace OpenMD {
  struct BendData {
    RealType angle;
    RealType potential;
  };
 
  struct BendDataSet {
    RealType deltaV;
    BendData prev;
    BendData curr;
  };
 
  class Bend : public ShortRangeInteraction {
  public:
    using ShortRangeInteraction::getPrevValue;
    using ShortRangeInteraction::getValue;
    Bend(Atom* atom1, Atom* atom2, Atom* atom3, BendType* bt) :
        ShortRangeInteraction(), bendType_(bt) {
      atoms_.resize(3);
      atoms_[0] = atom1;
      atoms_[1] = atom2;
      atoms_[2] = atom3;
    }
 
    virtual ~Bend() {}
    virtual void calcForce(RealType& angle, bool doParticlePot);
 
    RealType getValue(int snapshotNo) {
      Vector3d pos1 = atoms_[0]->getPos(snapshotNo);
      Vector3d pos2 = atoms_[1]->getPos(snapshotNo);
      Vector3d pos3 = atoms_[2]->getPos(snapshotNo);
 
      Vector3d r21 = pos1 - pos2;
      snapshotMan_->getSnapshot(snapshotNo)->wrapVector(r21);
      RealType d21 = r21.length();
 
      Vector3d r23 = pos3 - pos2;
      snapshotMan_->getSnapshot(snapshotNo)->wrapVector(r23);
      RealType d23 = r23.length();
 
      RealType cosTheta = dot(r21, r23) / (d21 * d23);
 
      // check roundoff
      if (cosTheta > 1.0) {
        cosTheta = 1.0;
      } else if (cosTheta < -1.0) {
        cosTheta = -1.0;
      }
 
      return acos(cosTheta);
    }
 
    RealType getPotential() { return potential_; }
 
    Atom* getAtomA() { return atoms_[0]; }
 
    Atom* getAtomB() { return atoms_[1]; }
 
    Atom* getAtomC() { return atoms_[2]; }
 
    BendType* getBendType() { return bendType_; }
 
    virtual std::string getName() { return name_; }
    /** Sets the name of this bend for selections */
    virtual void setName(const std::string& name) { name_ = name; }
 
    void accept(BaseVisitor* v) { v->visit(this); }
 
  protected:
    RealType potential_ {};
    BendType* bendType_; /**< bend type */
    std::string name_;
  };
}  // namespace OpenMD
 
#endif  // PRIMITIVES_BEND_HPP