include/physics.h

   1 /*
   2  * $Id$
   3  *
   4  *                This source code is part of
   5  *
   6  *                 G   R   O   M   A   C   S
   7  *
   8  *          GROningen MAchine for Chemical Simulations
   9  *
  10  *                        VERSION 3.2.0
  11  * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
  12  * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
  13  * Copyright (c) 2001-2004, The GROMACS development team,
  14  * check out http://www.gromacs.org for more information.
  15
  16  * This program is free software; you can redistribute it and/or
  17  * modify it under the terms of the GNU General Public License
  18  * as published by the Free Software Foundation; either version 2
  19  * of the License, or (at your option) any later version.
  20  *
  21  * If you want to redistribute modifications, please consider that
  22  * scientific software is very special. Version control is crucial -
  23  * bugs must be traceable. We will be happy to consider code for
  24  * inclusion in the official distribution, but derived work must not
  25  * be called official GROMACS. Details are found in the README & COPYING
  26  * files - if they are missing, get the official version at www.gromacs.org.
  27  *
  28  * To help us fund GROMACS development, we humbly ask that you cite
  29  * the papers on the package - you can find them in the top README file.
  30  *
  31  * For more info, check our website at http://www.gromacs.org
  32  *
  33  * And Hey:
  34  * Gromacs Runs On Most of All Computer Systems
  35  */
  36
  37 #ifndef _physics_h
  38 #define _physics_h
  39
  40 #ifdef HAVE_CONFIG_H
  41 #include <config.h>
  42 #endif
  43
  44 /*
  45  * Physical constants to be used in Gromacs.
  46  * No constants (apart from 0, 1 or 2) should
  47  * be anywhere else in the code.
  48  */
  49
  50 #include <math.h>
  51
  52 #ifndef M_PI
  53 #ifdef _PI
  54 #define M_PI _PI
  55 #else
  56 #define M_PI        3.14159265358979323846
  57 #endif
  58 #endif
  59
  60 #define ANGSTROM         (1e-10)                /* Old...       */
  61 #define KILO             (1e3)                  /* Thousand     */
  62 #define NANO             (1e-9)                 /* A Number     */
  63 #define PICO             (1e-12)                /* A Number     */
  64 #define A2NM             (ANGSTROM/NANO)        /* NANO         */
  65 #define NM2A             (NANO/ANGSTROM)        /* 10.0         */
  66 #define RAD2DEG          (180.0/M_PI)           /* Conversion   */
  67 #define DEG2RAD          (M_PI/180.0)           /* id           */
  68 #define CAL2JOULE        (4.184)                /* id           */
  69 #define E_CHARGE         (1.60217733e-19)       /* Coulomb      */
  70
  71 #define AMU              (1.6605402e-27)        /* kg           */
  72 #define BOLTZMANN        (1.380658e-23)         /* (J/K)        */
  73 #define AVOGADRO         (6.0221367e23)         /* ()           */
  74 #define RGAS             (BOLTZMANN*AVOGADRO)   /* (J/(mol K))  */
  75 #define BOLTZ            (RGAS/KILO)            /* (kJ/(mol K)) */
  76 #define FARADAY          (E_CHARGE*AVOGADRO)    /* (C/mol)      */
  77 #define ELECTRONVOLT     (E_CHARGE*AVOGADRO/KILO) /* (kJ/mol)   */
  78 #define PLANCK1          (6.6262e-34)           /* J s */
  79 #define PLANCK           (6.6262e-34*AVOGADRO/(PICO*KILO)) /* (kJ/mol) ps */
  80
  81 #define EPSILON0         (5.72765E-4)           /* (e^2 / Na (kJ nm))
  82                                                    == (e^2 mol/(kJ nm)) */
  83
  84 #define SPEED_OF_LIGHT   (2.9979245800E05)      /* nm/ps                */
  85 #define ATOMICMASS_keV   (940000.0)             /* Atomic mass in keV   */
  86 #define ELECTRONMASS_keV (512.0)                /* Electron mas in keV  */
  87
  88 #define FACEL            (332.0636*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 BORH2NM           0.0529177249
 101 #define HARTREE_BOHR2MD   (HARTREE2KJ*AVOGADRO/BORH2NM)
 102
 103 #endif  /* _physics_h */
 104
 105