src/gromacs/math/units.h

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  37 #ifndef GMX_MATH_UNITS_H
  38 #define GMX_MATH_UNITS_H
  39
  40 /*
  41  * Physical constants to be used in Gromacs.
  42  * No constants (apart from 0, 1 or 2) should
  43  * be anywhere else in the code.
  44  */
  45
  46 #include "utilities.h"
  47
  48 #ifdef __cplusplus
  49 extern "C" {
  50 #endif
  51
  52 #define ANGSTROM     (1e-10)                               /* Old...    */
  53 #define KILO         (1e3)                                 /* Thousand  */
  54 #define NANO         (1e-9)                                /* A Number  */
  55 #define PICO         (1e-12)                               /* A Number  */
  56 #define A2NM         (ANGSTROM/NANO)                       /* NANO              */
  57 #define NM2A         (NANO/ANGSTROM)                       /* 10.0              */
  58 #define RAD2DEG      (180.0/M_PI)                          /* Conversion        */
  59 #define DEG2RAD      (M_PI/180.0)                          /* id                */
  60 #define CAL2JOULE    (4.184)                               /* id                */
  61 #define E_CHARGE         (1.60217733e-19)                  /* Coulomb   */
  62
  63 #define AMU              (1.6605402e-27)                   /* kg           */
  64 #define BOLTZMANN    (1.380658e-23)                        /* (J/K)     */
  65 #define AVOGADRO     (6.0221367e23)                        /* ()                */
  66 #define RGAS             (BOLTZMANN*AVOGADRO)              /* (J/(mol K))  */
  67 #define BOLTZ            (RGAS/KILO)                       /* (kJ/(mol K)) */
  68 #define FARADAY          (E_CHARGE*AVOGADRO)               /* (C/mol)      */
  69 #define ELECTRONVOLT     (E_CHARGE*AVOGADRO/KILO)          /* (kJ/mol)   */
  70 #define PLANCK1          (6.6262e-34)                      /* J s */
  71 #define PLANCK           (6.6262e-34*AVOGADRO/(PICO*KILO)) /* (kJ/mol) ps */
  72
  73 #define EPSILON0     (5.72765E-4)                          /* (e^2 / Na (kJ nm))
  74                                                               == (e^2 mol/(kJ nm)) */
  75
  76 #define SPEED_OF_LIGHT   (2.9979245800E05)                 /* nm/ps                */
  77 #define ATOMICMASS_keV   (940000.0)                        /* Atomic mass in keV   */
  78 #define ELECTRONMASS_keV (512.0)                           /* Electron mas in keV  */
  79
  80 /* Improved accuracy (PL & EL, 20090421) */
  81 #define FACEL        (332.0636930*CAL2JOULE) /* (10 * (ONE_4PI_EPS0)) */
  82 #define ONE_4PI_EPS0     (FACEL*0.1)         /* 1/(4*pi*e0)*/
  83 #define PRESFAC           (16.6054)          /* bar / pressure unity */
  84 #define ENM2DEBYE         48.0321            /* Convert electron nm  *
  85                                               * to debye             */
  86 #define DEBYE2ENM         0.02081941
  87 /* to convert from a acceleration in (e V)/(amu nm) */
  88 /* FIELDFAC is also Faraday's constant and E_CHARGE/(1e6 AMU) */
  89 #define FIELDFAC          (FARADAY/KILO)
  90
  91 /* to convert AU to MD units: */
  92 #define HARTREE2KJ        4.3597482e-21
  93 #define BOHR2NM           0.0529177249
  94 #define HARTREE_BOHR2MD   (HARTREE2KJ*AVOGADRO/BOHR2NM)
  95
  96
  97 /* The four basic units */
  98 #define unit_length   "nm"
  99 #define unit_time     "ps"
 100 #define unit_mass     "u"
 101 #define unit_energy   "kJ/mol"
 102
 103 /* Temperature unit, T in this unit times BOLTZ give energy in unit_energy */
 104 #define unit_temp_K   "K"
 105
 106 /* Charge unit, electron charge, involves ONE_4PI_EPS0 */
 107 #define unit_charge_e "e"
 108
 109 /* Pressure unit, pressure in basic units times PRESFAC gives this unit */
 110 #define unit_pres_bar "bar"
 111
 112 /* Dipole unit, debye, conversion from the unit_charge_e involves ENM2DEBYE */
 113 #define unit_dipole_D "D"
 114
 115 /* Derived units from basic units only */
 116 #define unit_vel      unit_length "/" unit_time
 117 #define unit_volume   unit_length "^3"
 118 #define unit_invtime  "1/" unit_time
 119
 120 /* Other derived units */
 121 #define unit_surft_bar unit_pres_bar " " unit_length
 122
 123 /* SI units, conversion from basic units involves NANO, PICO and AMU */
 124 #define unit_length_SI  "m"
 125 #define unit_time_SI    "s"
 126 #define unit_mass_SI    "kg"
 127
 128 #define unit_density_SI unit_mass_SI "/" unit_length_SI "^3"
 129 #define unit_invvisc_SI unit_length_SI " " unit_time_SI "/" unit_mass_SI
 130
 131 /* The routines below can be used for converting units from or to GROMACS
 132    internal units. */
 133 enum {
 134     eg2cAngstrom, eg2cNm, eg2cBohr, eg2cKcal_Mole,
 135     eg2cHartree, eg2cHartree_e, eg2cAngstrom3, eg2cCoulomb,
 136     eg2cDebye, eg2cElectron, eg2cBuckingham, eg2cNR
 137 };
 138
 139 /* Convert value x to GROMACS units. Energy -> Energy, Length -> Length etc.
 140    The type of x is deduced from unit,
 141    which should be taken from the enum above. */
 142 extern double convert2gmx(double x, int unit);
 143
 144 /* Convert value x from GROMACS units to the desired one.
 145    The type of return value is deduced from unit, see above */
 146 extern double gmx2convert(double x, int unit);
 147
 148 /* Convert the string to one of the units supported. Returns -1 if not found. */
 149 extern int string2unit(char *string);
 150
 151 /* Convert the unit to a string. Return NULL when unit is out of range. */
 152 extern const char *unit2string(int unit);
 153
 154 #ifdef __cplusplus
 155 }
 156 #endif
 157
 158 #endif