MMFF94VanDerWaalsInteraction.hpp

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/* 
 * MMFF94VanDerWaalsInteraction.hpp 
 *
 * This file is part of the Chemical Data Processing Toolkit
 *
 * Copyright (C) 2003 Thomas Seidel <thomas.seidel@univie.ac.at>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; see the file COPYING. If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
 
#ifndef CDPL_FORCEFIELD_MMFF94VANDERWAALSINTERACTION_HPP
#define CDPL_FORCEFIELD_MMFF94VANDERWAALSINTERACTION_HPP
 
#include <cstddef>
#include <cmath>
 
 
namespace CDPL
{
 
    namespace ForceField
    {
 
        class MMFF94VanDerWaalsInteraction
        {
 
          public:
            enum HDonorAcceptorType
            {
 
                NONE,
                DONOR,
                ACCEPTOR
            };
 
            MMFF94VanDerWaalsInteraction(std::size_t atom1_idx, std::size_t atom2_idx,
                                         double atom_pol1, double eff_el_num1, double fact_a1, double fact_g1,
                                         HDonorAcceptorType don_acc_type1, double atom_pol2, double eff_el_num2,
                                         double fact_a2, double fact_g2, HDonorAcceptorType don_acc_type2,
                                         double expo, double fact_b, double beta, double fact_darad, double fact_daeps):
                atom1Idx(atom1_idx),
                atom2Idx(atom2_idx)
            {
 
                bool have_don     = false;
                bool have_don_acc = false;
 
                switch (don_acc_type1) {
 
                    case DONOR:
                        have_don     = true;
                        have_don_acc = (don_acc_type2 == ACCEPTOR);
                        break;
 
                    case ACCEPTOR:
                        have_don_acc = (don_acc_type2 == DONOR);
                        have_don     = have_don_acc;
                        break;
 
                    default:
                        have_don = (don_acc_type2 == DONOR);
                        break;
                }
 
                double rII = fact_a1 * std::pow(atom_pol1, expo);
                double rJJ = fact_a2 * std::pow(atom_pol2, expo);
                double gIJ = (rII - rJJ) / (rII + rJJ);
 
                rIJ = 0.5 * (rII + rJJ);
 
                if (!have_don)
                    rIJ += rIJ * fact_b * (1.0 - std::exp(-beta * gIJ * gIJ));
 
                eIJ = 181.16 * fact_g1 * fact_g2 * atom_pol1 * atom_pol2 / (std::pow(atom_pol1 / eff_el_num1, 0.5) + std::pow(atom_pol2 / eff_el_num2, 0.5)) * std::pow(rIJ, -6.0);
 
                if (have_don_acc) {
                    rIJ *= fact_darad;
                    eIJ *= fact_daeps;
                }
 
                rIJPow7 = std::pow(rIJ, 7.0);
            }
 
            std::size_t getAtom1Index() const
            {
                return atom1Idx;
            }
 
            std::size_t getAtom2Index() const
            {
                return atom2Idx;
            }
 
            double getEIJ() const
            {
                return eIJ;
            }
 
            double getRIJ() const
            {
                return rIJ;
            }
 
            double getRIJPow7() const
            {
                return rIJPow7;
            }
 
          private:
            std::size_t atom1Idx;
            std::size_t atom2Idx;
            double      eIJ;
            double      rIJ;
            double      rIJPow7;
        };
    } // namespace ForceField
} // namespace CDPL
 
#endif // CDPL_FORCEFIELD_MMFF94VANDERWAALSINTERACTION_HPP