src/gromacs/mdtypes/interaction_const.h

   1 /*
   2  * This file is part of the GROMACS molecular simulation package.
   3  *
   4  * Copyright (c) 2012,2013,2014,2015,2017 by the GROMACS development team.
   5  * Copyright (c) 2018,2019,2020, by the GROMACS development team, led by
   6  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
   7  * and including many others, as listed in the AUTHORS file in the
   8  * top-level source directory and at http://www.gromacs.org.
   9  *
  10  * GROMACS is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public License
  12  * as published by the Free Software Foundation; either version 2.1
  13  * of the License, or (at your option) any later version.
  14  *
  15  * GROMACS is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * Lesser General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public
  21  * License along with GROMACS; if not, see
  22  * http://www.gnu.org/licenses, or write to the Free Software Foundation,
  23  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA.
  24  *
  25  * If you want to redistribute modifications to GROMACS, please
  26  * consider that scientific software is very special. Version
  27  * control is crucial - bugs must be traceable. We will be happy to
  28  * consider code for inclusion in the official distribution, but
  29  * derived work must not be called official GROMACS. Details are found
  30  * in the README & COPYING files - if they are missing, get the
  31  * official version at http://www.gromacs.org.
  32  *
  33  * To help us fund GROMACS development, we humbly ask that you cite
  34  * the research papers on the package. Check out http://www.gromacs.org.
  35  */
  36 #ifndef GMX_MDTYPES_INTERACTION_CONST_H
  37 #define GMX_MDTYPES_INTERACTION_CONST_H
  38
  39 #include <memory>
  40 #include <vector>
  41
  42 #include "gromacs/mdtypes/md_enums.h"
  43 #include "gromacs/utility/alignedallocator.h"
  44 #include "gromacs/utility/basedefinitions.h"
  45 #include "gromacs/utility/real.h"
  46
  47 struct t_lambda;
  48
  49 /* Used with force switching or a constant potential shift:
  50  * rsw       = max(r - r_switch, 0)
  51  * force/p   = r^-(p+1) + c2*rsw^2 + c3*rsw^3
  52  * potential = r^-p + c2/3*rsw^3 + c3/4*rsw^4 + cpot
  53  * With a constant potential shift c2 and c3 are both 0.
  54  */
  55 struct shift_consts_t
  56 {
  57     real c2;
  58     real c3;
  59     real cpot;
  60 };
  61
  62 /* Used with potential switching:
  63  * rsw        = max(r - r_switch, 0)
  64  * sw         = 1 + c3*rsw^3 + c4*rsw^4 + c5*rsw^5
  65  * dsw        = 3*c3*rsw^2 + 4*c4*rsw^3 + 5*c5*rsw^4
  66  * force      = force*dsw - potential*sw
  67  * potential *= sw
  68  */
  69 struct switch_consts_t
  70 {
  71     real c3;
  72     real c4;
  73     real c5;
  74 };
  75
  76 /* Convenience type for vector with aligned memory */
  77 template<typename T>
  78 using AlignedVector = std::vector<T, gmx::AlignedAllocator<T>>;
  79
  80 /* Force/energy interpolation tables for Ewald long-range corrections
  81  *
  82  * Interpolation is linear for the force, quadratic for the potential.
  83  */
  84 struct EwaldCorrectionTables
  85 {
  86     // 1/table_spacing, units 1/nm
  87     real scale = 0;
  88     // Force table
  89     AlignedVector<real> tableF;
  90     // Energy table
  91     AlignedVector<real> tableV;
  92     // Coulomb force+energy table, size of array is tabq_size*4,
  93     // entry quadruplets are: F[i], F[i+1]-F[i], V[i], 0,
  94     // this is used with 4-wide SIMD for aligned loads
  95     AlignedVector<real> tableFDV0;
  96 };
  97
  98 /* The physical interaction parameters for non-bonded interaction calculations
  99  *
 100  * This struct contains copies of the physical interaction parameters
 101  * from the user input as well as processed values that are need in
 102  * non-bonded interaction kernels.
 103  *
 104  * The default constructor gives plain Coulomb and LJ interactions cut off
 105  * a 1 nm without potential shifting and a Coulomb pre-factor of 1.
 106  */
 107 struct interaction_const_t
 108 {
 109     /* This struct contains the soft-core parameters from t_lambda,
 110      * but processed for direct use in the kernels.
 111      */
 112     struct SoftCoreParameters
 113     {
 114         // Constructor
 115         SoftCoreParameters(const t_lambda& fepvals);
 116
 117         // Alpha parameter for Van der Waals interactions
 118         real alphaVdw;
 119         // Alpha parameter for Coulomb interactions
 120         real alphaCoulomb;
 121         // Exponent for the dependence of the soft-core on lambda
 122         int lambdaPower;
 123         // Value for sigma^6 for LJ interaction with C6<=0 and/or C12<=0
 124         real sigma6WithInvalidSigma;
 125         // Minimum value for sigma^6, used when soft-core is applied to Coulomb interactions
 126         real sigma6Minimum;
 127     };
 128
 129     /* VdW */
 130     int                    vdwtype          = evdwCUT;
 131     int                    vdw_modifier     = eintmodNONE;
 132     double                 reppow           = 12;
 133     real                   rvdw             = 1;
 134     real                   rvdw_switch      = 0;
 135     struct shift_consts_t  dispersion_shift = { 0, 0, 0 };
 136     struct shift_consts_t  repulsion_shift  = { 0, 0, 0 };
 137     struct switch_consts_t vdw_switch       = { 0, 0, 0 };
 138     gmx_bool               useBuckingham    = false;
 139     real                   buckinghamBMax   = 0;
 140
 141     /* type of electrostatics */
 142     int eeltype          = eelCUT;
 143     int coulomb_modifier = eintmodNONE;
 144
 145     /* Coulomb */
 146     real rcoulomb        = 1;
 147     real rcoulomb_switch = 0;
 148
 149     /* PME/Ewald */
 150     real ewaldcoeff_q    = 0;
 151     real ewaldcoeff_lj   = 0;
 152     int  ljpme_comb_rule = eljpmeGEOM; /* LJ combination rule for the LJ PME mesh part */
 153     real sh_ewald        = 0;          /* -sh_ewald is added to the direct space potential */
 154     real sh_lj_ewald     = 0;          /* sh_lj_ewald is added to the correction potential */
 155
 156     /* Dielectric constant resp. multiplication factor for charges */
 157     real epsilon_r = 1;
 158     real epsfac    = 1;
 159
 160     /* Constants for reaction-field or plain cut-off */
 161     real epsilon_rf = 1;
 162     real k_rf       = 0;
 163     real c_rf       = 0;
 164
 165     // Coulomb Ewald correction table
 166     std::unique_ptr<EwaldCorrectionTables> coulombEwaldTables;
 167     // Van der Waals Ewald correction table
 168     std::unique_ptr<EwaldCorrectionTables> vdwEwaldTables;
 169
 170     // Free-energy parameters, only present when free-energy calculations are requested
 171     std::unique_ptr<SoftCoreParameters> softCoreParameters;
 172 };
 173
 174 #endif