rigid_bond.hpp

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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/>.
 */
 
#pragma once
 
/** \file
 *  Definition of the rigid bond data type for the Rattle algorithm.
 */
 
#include <utils/Vector.hpp>
 
#include <cmath>
 
/** Parameters for the rigid_bond/SHAKE/RATTLE ALGORITHM */
struct RigidBond {
  /** Square of the length of Constrained Bond */
  double d2;
  /** Positional Tolerance/Accuracy value for termination of RATTLE/SHAKE
   *  iterations during position corrections
   */
  double p_tol;
  /** Velocity Tolerance/Accuracy for termination of RATTLE/SHAKE iterations
   *  during velocity corrections
   */
  double v_tol;
 
  double cutoff() const { return std::sqrt(d2); }
 
  static constexpr int num = 1;
 
  RigidBond(double d, double p_tol, double v_tol) {
    this->d2 = d * d;
    this->p_tol = 2.0 * p_tol;
    this->v_tol = v_tol;
  }
};