ESPResSo
Extensible Simulation Package for Research on Soft Matter Systems
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soft_sphere.hpp
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1/*
2 * Copyright (C) 2010-2022 The ESPResSo project
3 * Copyright (C) 2002,2003,2004,2005,2006,2007,2008,2009,2010
4 * Max-Planck-Institute for Polymer Research, Theory Group
5 *
6 * This file is part of ESPResSo.
7 *
8 * ESPResSo is free software: you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation, either version 3 of the License, or
11 * (at your option) any later version.
12 *
13 * ESPResSo is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program. If not, see <http://www.gnu.org/licenses/>.
20 */
21#ifndef soft_H
22#define soft_H
23
24/** \file
25 * Routines to calculate the soft-sphere potential between particle pairs.
26 *
27 * Implementation in \ref soft_sphere.cpp
28 */
29
30#include "config/config.hpp"
31
32#ifdef SOFT_SPHERE
33
35
36#include <cmath>
37
38/** Calculate soft-sphere force factor */
39inline double soft_pair_force_factor(IA_parameters const &ia_params,
40 double dist) {
41 if (dist < ia_params.soft_sphere.max_cutoff()) {
42 /* normal case: resulting force/energy smaller than zero. */
43 auto const r_off = dist - ia_params.soft_sphere.offset;
44 if (r_off > 0.0) {
45 auto const n = ia_params.soft_sphere.n;
46 return ia_params.soft_sphere.a * n / std::pow(r_off, n + 1) / dist;
47 }
48 }
49 return 0.0;
50}
51
52/** Calculate soft-sphere energy */
53inline double soft_pair_energy(IA_parameters const &ia_params, double dist) {
54 if (dist < ia_params.soft_sphere.max_cutoff()) {
55 auto const r_off = dist - ia_params.soft_sphere.offset;
56 /* normal case: resulting force/energy smaller than zero. */
57 return ia_params.soft_sphere.a / std::pow(r_off, ia_params.soft_sphere.n);
58 }
59 return 0.0;
60}
61
62#endif // SOFT_SPHERE
63#endif
This file contains the defaults for ESPResSo.
Various procedures concerning interactions between particles.
double soft_pair_force_factor(IA_parameters const &ia_params, double dist)
Calculate soft-sphere force factor.
double soft_pair_energy(IA_parameters const &ia_params, double dist)
Calculate soft-sphere energy.
Parameters for non-bonded interactions.
SoftSphere_Parameters soft_sphere