include/physics.h

   1 /*
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  38
  39 #ifndef _physics_h
  40 #define _physics_h
  41
  42 /*
  43  * Physical constants to be used in Gromacs.
  44  * No constants (apart from 0, 1 or 2) should
  45  * be anywhere else in the code.
  46  */
  47
  48 #include <math.h>
  49
  50 /* we do it anyway. */
  51 #ifdef __cplusplus
  52 extern "C" {
  53 #endif
  54
  55 #ifndef M_PI
  56 #ifdef _PI
  57 #define M_PI _PI
  58 #else
  59 #define M_PI        3.14159265358979323846
  60 #endif
  61 #endif
  62
  63 #define ANGSTROM         (1e-10)                /* Old...       */
  64 #define KILO             (1e3)                  /* Thousand     */
  65 #define NANO             (1e-9)                 /* A Number     */
  66 #define PICO             (1e-12)                /* A Number     */
  67 #define A2NM             (ANGSTROM/NANO)        /* NANO         */
  68 #define NM2A             (NANO/ANGSTROM)        /* 10.0         */
  69 #define RAD2DEG          (180.0/M_PI)           /* Conversion   */
  70 #define DEG2RAD          (M_PI/180.0)           /* id           */
  71 #define CAL2JOULE        (4.184)                /* id           */
  72 #define E_CHARGE         (1.60217733e-19)       /* Coulomb      */
  73
  74 #define AMU              (1.6605402e-27)        /* kg           */
  75 #define BOLTZMANN        (1.380658e-23)         /* (J/K)        */
  76 #define AVOGADRO         (6.0221367e23)         /* ()           */
  77 #define RGAS             (BOLTZMANN*AVOGADRO)   /* (J/(mol K))  */
  78 #define BOLTZ            (RGAS/KILO)            /* (kJ/(mol K)) */
  79 #define FARADAY          (E_CHARGE*AVOGADRO)    /* (C/mol)      */
  80 #define ELECTRONVOLT     (E_CHARGE*AVOGADRO/KILO) /* (kJ/mol)   */
  81 #define PLANCK1          (6.6262e-34)           /* J s */
  82 #define PLANCK           (6.6262e-34*AVOGADRO/(PICO*KILO)) /* (kJ/mol) ps */
  83
  84 #define EPSILON0         (5.72765E-4)           /* (e^2 / Na (kJ nm))
  85                                                    == (e^2 mol/(kJ nm)) */
  86
  87 #define SPEED_OF_LIGHT   (2.9979245800E05)      /* nm/ps                */
  88 #define ATOMICMASS_keV   (940000.0)             /* Atomic mass in keV   */
  89 #define ELECTRONMASS_keV (512.0)                /* Electron mas in keV  */
  90
  91 /* Improved accuracy (PL & EL, 20090421) */
  92 #define FACEL            (332.0636930*CAL2JOULE)/* (10 * (ONE_4PI_EPS0)) */
  93 #define ONE_4PI_EPS0     (FACEL*0.1)            /* 1/(4*pi*e0)*/
  94 #define PRESFAC           (16.6054)             /* bar / pressure unity */
  95 #define ENM2DEBYE         48.0321               /* Convert electron nm  *
  96                                                  * to debye             */
  97 #define DEBYE2ENM         0.02081941
  98 /* to convert from a acceleration in (e V)/(amu nm) */
  99 /* FIELDFAC is also Faraday's constant and E_CHARGE/(1e6 AMU) */
 100 #define FIELDFAC          (FARADAY/KILO)
 101
 102 /* to convert AU to MD units: */
 103 #define HARTREE2KJ        4.3597482e-21
 104 #define BOHR2NM           0.0529177249
 105 #define HARTREE_BOHR2MD   (HARTREE2KJ*AVOGADRO/BOHR2NM)
 106
 107
 108 /* The four basic units */
 109 #define unit_length   "nm"
 110 #define unit_time     "ps"
 111 #define unit_mass     "u"
 112 #define unit_energy   "kJ/mol"
 113
 114 /* Temperature unit, T in this unit times BOLTZ give energy in unit_energy */
 115 #define unit_temp_K   "K"
 116
 117 /* Charge unit, electron charge, involves ONE_4PI_EPS0 */
 118 #define unit_charge_e "e"
 119
 120 /* Pressure unit, pressure in basic units times PRESFAC gives this unit */
 121 #define unit_pres_bar "bar"
 122
 123 /* Dipole unit, debye, conversion from the unit_charge_e involves ENM2DEBYE */
 124 #define unit_dipole_D "D"
 125
 126 /* Derived units from basic units only */
 127 #define unit_vel      unit_length "/" unit_time
 128 #define unit_volume   unit_length "^3"
 129 #define unit_invtime  "1/" unit_time
 130
 131 /* Other derived units */
 132 #define unit_surft_bar unit_pres_bar " " unit_length
 133
 134 /* SI units, conversion from basic units involves NANO, PICO and AMU */
 135 #define unit_length_SI  "m"
 136 #define unit_time_SI    "s"
 137 #define unit_mass_SI    "kg"
 138
 139 #define unit_density_SI unit_mass_SI "/" unit_length_SI "^3"
 140 #define unit_invvisc_SI unit_length_SI " " unit_time_SI "/" unit_mass_SI
 141
 142   /* The routines below can be used for converting units from or to GROMACS
 143      internal units. */
 144   enum { eg2cAngstrom, eg2cNm, eg2cBohr, eg2cKcal_Mole,
 145          eg2cHartree, eg2cHartree_e, eg2cAngstrom3, eg2cCoulomb,
 146          eg2cDebye, eg2cElectron, eg2cBuckingham, eg2cNR };
 147
 148   /* Convert value x to GROMACS units. Energy -> Energy, Length -> Length etc.
 149      The type of x is deduced from unit,
 150      which should be taken from the enum above. */
 151   extern double convert2gmx(double x,int unit);
 152
 153   /* Convert value x from GROMACS units to the desired one.
 154      The type of return value is deduced from unit, see above */
 155   extern double gmx2convert(double x,int unit);
 156
 157   /* Convert the string to one of the units supported. Returns -1 if not found. */
 158   extern int string2unit(char *string);
 159
 160   /* Convert the unit to a string. Return NULL when unit is out of range. */
 161   extern const char *unit2string(int unit);
 162
 163 #ifdef __cplusplus
 164 }
 165 #endif
 166
 167
 168 #endif  /* _physics_h */
 169
 170