ESPResSo
Extensible Simulation Package for Research on Soft Matter Systems
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ljcos.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 CORE_NB_IA_LJCOS_HPP
22#define CORE_NB_IA_LJCOS_HPP
23/** \file
24 * Routines to calculate the Lennard-Jones+cosine potential between
25 * particle pairs.
26 *
27 * Implementation in \ref ljcos.cpp.
28 */
29
30#include "config/config.hpp"
31
32#ifdef LJCOS
33
35
37#include <utils/math/sqr.hpp>
38
39#include <cmath>
40
41/** Calculate Lennard-Jones cosine force factor */
42inline double ljcos_pair_force_factor(IA_parameters const &ia_params,
43 double dist) {
44 auto fac = 0.0;
45 if (dist < (ia_params.ljcos.cut + ia_params.ljcos.offset)) {
46 auto const r_off = dist - ia_params.ljcos.offset;
47 /* cos part of ljcos potential. */
48 if (dist > ia_params.ljcos.rmin + ia_params.ljcos.offset) {
49 fac = (r_off / dist) * ia_params.ljcos.alfa * ia_params.ljcos.eps *
50 (sin(ia_params.ljcos.alfa * Utils::sqr(r_off) +
51 ia_params.ljcos.beta));
52 }
53 /* Lennard-Jones part of the potential. */
54 else if (dist > 0) {
55 auto const frac6 = Utils::int_pow<6>(ia_params.ljcos.sig / r_off);
56 fac = 48.0 * ia_params.ljcos.eps * frac6 * (frac6 - 0.5) / (r_off * dist);
57 }
58 }
59 return fac;
60}
61
62/** Calculate Lennard-Jones cosine energy */
63inline double ljcos_pair_energy(IA_parameters const &ia_params, double dist) {
64 if (dist < (ia_params.ljcos.cut + ia_params.ljcos.offset)) {
65 auto const r_off = dist - ia_params.ljcos.offset;
66 /* Lennard-Jones part of the potential. */
67 if (dist < (ia_params.ljcos.rmin + ia_params.ljcos.offset)) {
68 auto const frac6 = Utils::int_pow<6>(ia_params.ljcos.sig / r_off);
69 return 4.0 * ia_params.ljcos.eps * (Utils::sqr(frac6) - frac6);
70 }
71 /* cosine part of the potential. */
72 return .5 * ia_params.ljcos.eps *
73 (cos(ia_params.ljcos.alfa * Utils::sqr(r_off) +
74 ia_params.ljcos.beta) -
75 1.);
76 }
77 return 0.0;
78}
79
80#endif // LJCOS
81#endif
This file contains the defaults for ESPResSo.
double ljcos_pair_force_factor(IA_parameters const &ia_params, double dist)
Calculate Lennard-Jones cosine force factor.
Definition ljcos.hpp:42
double ljcos_pair_energy(IA_parameters const &ia_params, double dist)
Calculate Lennard-Jones cosine energy.
Definition ljcos.hpp:63
DEVICE_QUALIFIER constexpr T sqr(T x)
Calculates the SQuaRe of x.
Definition sqr.hpp:28
Various procedures concerning interactions between particles.
Parameters for non-bonded interactions.