morse.cpp

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/*
 * Copyright (C) 2010-2022 The ESPResSo project
 * Copyright (C) 2002,2003,2004,2005,2006,2007,2008,2009,2010
 *   Max-Planck-Institute for Polymer Research, Theory Group
 *
 * This file is part of ESPResSo.
 *
 * ESPResSo is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * ESPResSo 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/** \file
 *
 *  Implementation of \ref morse.hpp
 */
#include "morse.hpp"
 
#ifdef MORSE
#include "nonbonded_interaction_data.hpp"
 
#include <cmath>
#include <stdexcept>
 
Morse_Parameters::Morse_Parameters(double eps, double alpha, double rmin,
                                   double cutoff)
    : eps{eps}, alpha{alpha}, rmin{rmin}, cut{cutoff} {
  if (eps < 0.) {
    throw std::domain_error("Morse parameter 'eps' has to be >= 0");
  }
  if (cutoff < 0.) {
    throw std::domain_error("Morse parameter 'cutoff' has to be >= 0");
  }
  auto const add1 = std::exp(-2.0 * alpha * (cut - rmin));
  auto const add2 = 2.0 * std::exp(-alpha * (cut - rmin));
  rest = eps * (add1 - add2);
}
 
#endif // MORSE