include/physics.h

   1 /*
   2  *
   3  *                This source code is part of
   4  *
   5  *                 G   R   O   M   A   C   S
   6  *
   7  *          GROningen MAchine for Chemical Simulations
   8  *
   9  *                        VERSION 3.2.0
  10  * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
  11  * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
  12  * Copyright (c) 2001-2004, The GROMACS development team,
  13  * check out http://www.gromacs.org for more information.
  14
  15  * This program is free software; you can redistribute it and/or
  16  * modify it under the terms of the GNU General Public License
  17  * as published by the Free Software Foundation; either version 2
  18  * of the License, or (at your option) any later version.
  19  *
  20  * If you want to redistribute modifications, please consider that
  21  * scientific software is very special. Version control is crucial -
  22  * bugs must be traceable. We will be happy to consider code for
  23  * inclusion in the official distribution, but derived work must not
  24  * be called official GROMACS. Details are found in the README & COPYING
  25  * files - if they are missing, get the official version at www.gromacs.org.
  26  *
  27  * To help us fund GROMACS development, we humbly ask that you cite
  28  * the papers on the package - you can find them in the top README file.
  29  *
  30  * For more info, check our website at http://www.gromacs.org
  31  *
  32  * And Hey:
  33  * Gromacs Runs On Most of All Computer Systems
  34  */
  35
  36 #ifndef _physics_h
  37 #define _physics_h
  38
  39 #ifdef HAVE_CONFIG_H
  40 #include <config.h>
  41 #endif
  42
  43 /*
  44  * Physical constants to be used in Gromacs.
  45  * No constants (apart from 0, 1 or 2) should
  46  * be anywhere else in the code.
  47  */
  48
  49 #include <math.h>
  50
  51 #ifndef M_PI
  52 #ifdef _PI
  53 #define M_PI _PI
  54 #else
  55 #define M_PI        3.14159265358979323846
  56 #endif
  57 #endif
  58
  59 #define ANGSTROM         (1e-10)                /* Old...       */
  60 #define KILO             (1e3)                  /* Thousand     */
  61 #define NANO             (1e-9)                 /* A Number     */
  62 #define PICO             (1e-12)                /* A Number     */
  63 #define A2NM             (ANGSTROM/NANO)        /* NANO         */
  64 #define NM2A             (NANO/ANGSTROM)        /* 10.0         */
  65 #define RAD2DEG          (180.0/M_PI)           /* Conversion   */
  66 #define DEG2RAD          (M_PI/180.0)           /* id           */
  67 #define CAL2JOULE        (4.184)                /* id           */
  68 #define E_CHARGE         (1.60217733e-19)       /* Coulomb      */
  69
  70 #define AMU              (1.6605402e-27)        /* kg           */
  71 #define BOLTZMANN        (1.380658e-23)         /* (J/K)        */
  72 #define AVOGADRO         (6.0221367e23)         /* ()           */
  73 #define RGAS             (BOLTZMANN*AVOGADRO)   /* (J/(mol K))  */
  74 #define BOLTZ            (RGAS/KILO)            /* (kJ/(mol K)) */
  75 #define FARADAY          (E_CHARGE*AVOGADRO)    /* (C/mol)      */
  76 #define ELECTRONVOLT     (E_CHARGE*AVOGADRO/KILO) /* (kJ/mol)   */
  77 #define PLANCK1          (6.6262e-34)           /* J s */
  78 #define PLANCK           (6.6262e-34*AVOGADRO/(PICO*KILO)) /* (kJ/mol) ps */
  79
  80 #define EPSILON0         (5.72765E-4)           /* (e^2 / Na (kJ nm))
  81                                                    == (e^2 mol/(kJ nm)) */
  82
  83 #define SPEED_OF_LIGHT   (2.9979245800E05)      /* nm/ps                */
  84 #define ATOMICMASS_keV   (940000.0)             /* Atomic mass in keV   */
  85 #define ELECTRONMASS_keV (512.0)                /* Electron mas in keV  */
  86
  87 /* Improved accuracy (PL & EL, 20090421) */
  88 #define FACEL            (332.0636930*CAL2JOULE)/* (10 * (ONE_4PI_EPS0)) */
  89 #define ONE_4PI_EPS0     (FACEL*0.1)            /* 1/(4*pi*e0)*/
  90 #define PRESFAC           (16.6054)             /* bar / pressure unity */
  91 #define ENM2DEBYE         48.0321               /* Convert electron nm  *
  92                                                  * to debye             */
  93 #define DEBYE2ENM         0.02081941
  94 /* to convert from a acceleration in (e V)/(amu nm) */
  95 /* FIELDFAC is also Faraday's constant and E_CHARGE/(1e6 AMU) */
  96 #define FIELDFAC          (FARADAY/KILO)
  97
  98 /* to convert AU to MD units: */
  99 #define HARTREE2KJ        4.3597482e-21
 100 #define BOHR2NM           0.0529177249
 101 #define HARTREE_BOHR2MD   (HARTREE2KJ*AVOGADRO/BOHR2NM)
 102
 103
 104 /* The four basic units */
 105 #define unit_length   "nm"
 106 #define unit_time     "ps"
 107 #define unit_mass     "u"
 108 #define unit_energy   "kJ/mol"
 109
 110 /* Temperature unit, T in this unit times BOLTZ give energy in unit_energy */
 111 #define unit_temp_K   "K"
 112
 113 /* Charge unit, electron charge, involves ONE_4PI_EPS0 */
 114 #define unit_charge_e "e"
 115
 116 /* Pressure unit, pressure in basic units times PRESFAC gives this unit */
 117 #define unit_pres_bar "bar"
 118
 119 /* Dipole unit, debye, conversion from the unit_charge_e involves ENM2DEBYE */
 120 #define unit_dipole_D "D"
 121
 122 /* Derived units from basic units only */
 123 #define unit_vel      unit_length "/" unit_time
 124 #define unit_volume   unit_length "^3"
 125 #define unit_invtime  "1/" unit_time
 126
 127 /* Other derived units */
 128 #define unit_surft_bar unit_pres_bar " " unit_length
 129
 130 /* SI units, conversion from basic units involves NANO, PICO and AMU */
 131 #define unit_length_SI  "m"
 132 #define unit_time_SI    "s"
 133 #define unit_mass_SI    "kg"
 134
 135 #define unit_density_SI unit_mass_SI "/" unit_length_SI "^3"
 136 #define unit_invvisc_SI unit_length_SI " " unit_time_SI "/" unit_mass_SI
 137
 138 #endif  /* _physics_h */
 139
 140