include/physics.h

   1 /*
   2  *
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   5  *                 G   R   O   M   A   C   S
   6  *
   7  *          GROningen MAchine for Chemical Simulations
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   9  *                        VERSION 3.2.0
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  13  * check out http://www.gromacs.org for more information.
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  35
  36 #ifndef _physics_h
  37 #define _physics_h
  38
  39 /*
  40  * Physical constants to be used in Gromacs.
  41  * No constants (apart from 0, 1 or 2) should
  42  * be anywhere else in the code.
  43  */
  44
  45 #include <math.h>
  46
  47 /* we do it anyway. */
  48 #ifdef __cplusplus
  49 extern "C" {
  50 #endif
  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 /* Improved accuracy (PL & EL, 20090421) */
  89 #define FACEL            (332.0636930*CAL2JOULE)/* (10 * (ONE_4PI_EPS0)) */
  90 #define ONE_4PI_EPS0     (FACEL*0.1)            /* 1/(4*pi*e0)*/
  91 #define PRESFAC           (16.6054)             /* bar / pressure unity */
  92 #define ENM2DEBYE         48.0321               /* Convert electron nm  *
  93                                                  * to debye             */
  94 #define DEBYE2ENM         0.02081941
  95 /* to convert from a acceleration in (e V)/(amu nm) */
  96 /* FIELDFAC is also Faraday's constant and E_CHARGE/(1e6 AMU) */
  97 #define FIELDFAC          (FARADAY/KILO)
  98
  99 /* to convert AU to MD units: */
 100 #define HARTREE2KJ        4.3597482e-21
 101 #define BOHR2NM           0.0529177249
 102 #define HARTREE_BOHR2MD   (HARTREE2KJ*AVOGADRO/BOHR2NM)
 103
 104
 105 /* The four basic units */
 106 #define unit_length   "nm"
 107 #define unit_time     "ps"
 108 #define unit_mass     "u"
 109 #define unit_energy   "kJ/mol"
 110
 111 /* Temperature unit, T in this unit times BOLTZ give energy in unit_energy */
 112 #define unit_temp_K   "K"
 113
 114 /* Charge unit, electron charge, involves ONE_4PI_EPS0 */
 115 #define unit_charge_e "e"
 116
 117 /* Pressure unit, pressure in basic units times PRESFAC gives this unit */
 118 #define unit_pres_bar "bar"
 119
 120 /* Dipole unit, debye, conversion from the unit_charge_e involves ENM2DEBYE */
 121 #define unit_dipole_D "D"
 122
 123 /* Derived units from basic units only */
 124 #define unit_vel      unit_length "/" unit_time
 125 #define unit_volume   unit_length "^3"
 126 #define unit_invtime  "1/" unit_time
 127
 128 /* Other derived units */
 129 #define unit_surft_bar unit_pres_bar " " unit_length
 130
 131 /* SI units, conversion from basic units involves NANO, PICO and AMU */
 132 #define unit_length_SI  "m"
 133 #define unit_time_SI    "s"
 134 #define unit_mass_SI    "kg"
 135
 136 #define unit_density_SI unit_mass_SI "/" unit_length_SI "^3"
 137 #define unit_invvisc_SI unit_length_SI " " unit_time_SI "/" unit_mass_SI
 138
 139   /* The routines below can be used for converting units from or to GROMACS
 140      internal units. */
 141   enum { eg2cAngstrom, eg2cNm, eg2cBohr, eg2cKcal_Mole,
 142          eg2cHartree, eg2cHartree_e, eg2cAngstrom3, eg2cCoulomb,
 143          eg2cDebye, eg2cElectron, eg2cBuckingham, eg2cNR };
 144
 145   /* Convert value x to GROMACS units. Energy -> Energy, Length -> Length etc.
 146      The type of x is deduced from unit,
 147      which should be taken from the enum above. */
 148   extern double convert2gmx(double x,int unit);
 149
 150   /* Convert value x from GROMACS units to the desired one.
 151      The type of return value is deduced from unit, see above */
 152   extern double gmx2convert(double x,int unit);
 153
 154   /* Convert the string to one of the units supported. Returns -1 if not found. */
 155   extern int string2unit(char *string);
 156
 157   /* Convert the unit to a string. Return NULL when unit is out of range. */
 158   extern const char *unit2string(int unit);
 159
 160 #ifdef __cplusplus
 161 }
 162 #endif
 163
 164
 165 #endif  /* _physics_h */
 166
 167