/usr/include/gromacs/physics.h

/*
 * This file is part of the GROMACS molecular simulation package.
 *
 * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
 * Copyright (c) 2001-2004, The GROMACS development team,
 * check out http://www.gromacs.org for more information.
 * Copyright (c) 2012,2013, by the GROMACS development team, led by
 * David van der Spoel, Berk Hess, Erik Lindahl, and including many
 * others, as listed in the AUTHORS file in the top-level source
 * directory and at http://www.gromacs.org.
 *
 * GROMACS is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 *
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
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 * License along with GROMACS; if not, see
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 */

#ifndef _physics_h
#define _physics_h

/*
 * Physical constants to be used in Gromacs.
 * No constants (apart from 0, 1 or 2) should
 * be anywhere else in the code.
 */

#include <math.h>

/* we do it anyway. */
#ifdef __cplusplus
extern "C" {
#endif

#ifndef M_PI
#ifdef _PI
#define M_PI _PI
#else
#define M_PI        3.14159265358979323846
#endif
#endif

#define ANGSTROM     (1e-10)                               /* Old...	*/
#define KILO         (1e3)                                 /* Thousand	*/
#define NANO         (1e-9)                                /* A Number	*/
#define PICO         (1e-12)                               /* A Number	*/
#define A2NM         (ANGSTROM/NANO)                       /* NANO	        */
#define NM2A         (NANO/ANGSTROM)                       /* 10.0		*/
#define RAD2DEG      (180.0/M_PI)                          /* Conversion	*/
#define DEG2RAD      (M_PI/180.0)                          /* id		*/
#define CAL2JOULE    (4.184)                               /* id		*/
#define E_CHARGE         (1.60217733e-19)                  /* Coulomb	*/

#define AMU              (1.6605402e-27)                   /* kg           */
#define BOLTZMANN    (1.380658e-23)                        /* (J/K)	*/
#define AVOGADRO     (6.0221367e23)                        /* ()		*/
#define RGAS             (BOLTZMANN*AVOGADRO)              /* (J/(mol K))  */
#define BOLTZ            (RGAS/KILO)                       /* (kJ/(mol K)) */
#define FARADAY          (E_CHARGE*AVOGADRO)               /* (C/mol)      */
#define ELECTRONVOLT     (E_CHARGE*AVOGADRO/KILO)          /* (kJ/mol)   */
#define PLANCK1          (6.6262e-34)                      /* J s */
#define PLANCK           (6.6262e-34*AVOGADRO/(PICO*KILO)) /* (kJ/mol) ps */

#define EPSILON0     (5.72765E-4)                          /* (e^2 / Na (kJ nm))
                                                              == (e^2 mol/(kJ nm)) */

#define SPEED_OF_LIGHT   (2.9979245800E05)                 /* nm/ps                */
#define ATOMICMASS_keV   (940000.0)                        /* Atomic mass in keV   */
#define ELECTRONMASS_keV (512.0)                           /* Electron mas in keV  */

/* Improved accuracy (PL & EL, 20090421) */
#define FACEL        (332.0636930*CAL2JOULE) /* (10 * (ONE_4PI_EPS0)) */
#define ONE_4PI_EPS0     (FACEL*0.1)         /* 1/(4*pi*e0)*/
#define PRESFAC           (16.6054)          /* bar / pressure unity */
#define ENM2DEBYE         48.0321            /* Convert electron nm  *
                                              * to debye             */
#define DEBYE2ENM         0.02081941
/* to convert from a acceleration in (e V)/(amu nm) */
/* FIELDFAC is also Faraday's constant and E_CHARGE/(1e6 AMU) */
#define FIELDFAC          (FARADAY/KILO)

/* to convert AU to MD units: */
#define HARTREE2KJ        4.3597482e-21
#define BOHR2NM           0.0529177249
#define HARTREE_BOHR2MD   (HARTREE2KJ*AVOGADRO/BOHR2NM)


/* The four basic units */
#define unit_length   "nm"
#define unit_time     "ps"
#define unit_mass     "u"
#define unit_energy   "kJ/mol"

/* Temperature unit, T in this unit times BOLTZ give energy in unit_energy */
#define unit_temp_K   "K"

/* Charge unit, electron charge, involves ONE_4PI_EPS0 */
#define unit_charge_e "e"

/* Pressure unit, pressure in basic units times PRESFAC gives this unit */
#define unit_pres_bar "bar"

/* Dipole unit, debye, conversion from the unit_charge_e involves ENM2DEBYE */
#define unit_dipole_D "D"

/* Derived units from basic units only */
#define unit_vel      unit_length "/" unit_time
#define unit_volume   unit_length "^3"
#define unit_invtime  "1/" unit_time

/* Other derived units */
#define unit_surft_bar unit_pres_bar " " unit_length

/* SI units, conversion from basic units involves NANO, PICO and AMU */
#define unit_length_SI  "m"
#define unit_time_SI    "s"
#define unit_mass_SI    "kg"

#define unit_density_SI unit_mass_SI "/" unit_length_SI "^3"
#define unit_invvisc_SI unit_length_SI " " unit_time_SI "/" unit_mass_SI

/* The routines below can be used for converting units from or to GROMACS
   internal units. */
enum {
    eg2cAngstrom, eg2cNm, eg2cBohr, eg2cKcal_Mole,
    eg2cHartree, eg2cHartree_e, eg2cAngstrom3, eg2cCoulomb,
    eg2cDebye, eg2cElectron, eg2cBuckingham, eg2cNR
};

/* Convert value x to GROMACS units. Energy -> Energy, Length -> Length etc.
   The type of x is deduced from unit,
   which should be taken from the enum above. */
extern double convert2gmx(double x, int unit);

/* Convert value x from GROMACS units to the desired one.
   The type of return value is deduced from unit, see above */
extern double gmx2convert(double x, int unit);

/* Convert the string to one of the units supported. Returns -1 if not found. */
extern int string2unit(char *string);

/* Convert the unit to a string. Return NULL when unit is out of range. */
extern const char *unit2string(int unit);

#ifdef __cplusplus
}
#endif


#endif  /* _physics_h */
gromacs-dev 4.6.5-1build1 / usr / include / gromacs / physics.h
