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Check out http://www.gromacs.org. 36 */ 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 "gromacs/math/utilities.h" 47 48 #define ANGSTROM (1e-10) /* Old... */ 49 #define KILO (1e3) /* Thousand */ 50 #define NANO (1e-9) /* A Number */ 51 #define PICO (1e-12) /* A Number */ 52 #define A2NM (ANGSTROM / NANO) /* NANO */ 53 #define NM2A (NANO / ANGSTROM) /* 10.0 */ 54 #define RAD2DEG (180.0 / M_PI) /* Conversion */ 55 #define DEG2RAD (M_PI / 180.0) /* id */ 56 #define CAL2JOULE (4.184) /* Exact definition of the calorie */ 57 #define E_CHARGE (1.602176634e-19) /* Exact definition, Coulomb NIST 2018 CODATA */ 58 59 #define AMU (1.66053906660e-27) /* kg, NIST 2018 CODATA */ 60 #define BOLTZMANN (1.380649e-23) /* (J/K, Exact definition, NIST 2018 CODATA */ 61 #define AVOGADRO (6.02214076e23) /* 1/mol, Exact definition, NIST 2018 CODATA */ 62 #define RGAS (BOLTZMANN * AVOGADRO) /* (J/(mol K)) */ 63 #define BOLTZ (RGAS / KILO) /* (kJ/(mol K)) */ 64 #define FARADAY (E_CHARGE * AVOGADRO) /* (C/mol) */ 65 #define ELECTRONVOLT (E_CHARGE * AVOGADRO / KILO) /* (kJ/mol) */ 66 #define PLANCK1 (6.62607015e-34) /* J/Hz, Exact definition, NIST 2018 CODATA */ 67 #define PLANCK (PLANCK1 * AVOGADRO / (PICO * KILO)) /* (kJ/mol) ps */ 68 69 #define EPSILON0_SI (8.8541878128e-12) /* F/m, NIST 2018 CODATA */ 70 /* Epsilon in our MD units: (e^2 / Na (kJ nm)) == (e^2 mol/(kJ nm)) */ 71 #define EPSILON0 ((EPSILON0_SI * NANO * KILO) / (E_CHARGE * E_CHARGE * AVOGADRO)) 72 73 #define SPEED_OF_LIGHT (2.99792458e05) /* units of nm/ps, Exact definition, NIST 2018 CODATA */ 74 #define ATOMICMASS_keV (931494.10242) /* Atomic mass in keV, NIST 2018 CODATA */ 75 #define ELECTRONMASS_keV (510.99895000) /* Electron mas in keV, NIST 2018 CODATA */ 76 77 #define RYDBERG (1.0973731568160e-02) /* nm^-1, NIST 2018 CODATA */ 78 79 #define ONE_4PI_EPS0 (1.0 / (4.0 * M_PI * EPSILON0)) 80 #define FACEL (10.0 * ONE_4PI_EPS0) 81 82 /* Pressure in MD units is: 83 * 1 bar = 1e5 Pa = 1e5 kg m^-1 s^-2 = 1e-28 kg nm^-1 ps^-2 = 1e-28 / AMU amu nm^1 ps ^2 84 */ 85 #define BAR_MDUNITS (1e5 * NANO * PICO * PICO / AMU) 86 #define PRESFAC (1.0 / BAR_MDUNITS) 87 88 /* DEBYE2ENM should be (1e-21*PICO)/(SPEED_OF_LIGHT*E_CHARGE*NANO*NANO), 89 * but we need to factor out some of the exponents to avoid single-precision overflows. 90 */ 91 #define DEBYE2ENM (1e-15 / (SPEED_OF_LIGHT * E_CHARGE)) 92 #define ENM2DEBYE (1.0 / DEBYE2ENM) 93 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 ((2.0 * RYDBERG * PLANCK * SPEED_OF_LIGHT) / AVOGADRO) 100 #define BOHR2NM (0.0529177210903) /* nm^-1, NIST 2018 CODATA */ 101 #define HARTREE_BOHR2MD (HARTREE2KJ * AVOGADRO / BOHR2NM) 102 103 104 /* The four basic units */ 105 #define unit_length "nm" 106 #define unit_time "ps" 107 #define unit_mass "u" 108 #define unit_energy "kJ/mol" 109 110 /* Temperature unit, T in this unit times BOLTZ give energy in unit_energy */ 111 #define unit_temp_K "K" 112 113 /* Charge unit, electron charge, involves ONE_4PI_EPS0 */ 114 #define unit_charge_e "e" 115 116 /* Pressure unit, pressure in basic units times PRESFAC gives this unit */ 117 #define unit_pres_bar "bar" 118 119 /* Dipole unit, debye, conversion from the unit_charge_e involves ENM2DEBYE */ 120 #define unit_dipole_D "D" 121 122 /* Derived units from basic units only */ 123 #define unit_vel unit_length "/" unit_time 124 #define unit_volume unit_length "^3" 125 #define unit_invtime "1/" unit_time 126 127 /* Other derived units */ 128 #define unit_surft_bar unit_pres_bar " " unit_length 129 130 /* SI units, conversion from basic units involves NANO, PICO and AMU */ 131 #define unit_length_SI "m" 132 #define unit_time_SI "s" 133 #define unit_mass_SI "kg" 134 135 #define unit_density_SI unit_mass_SI "/" unit_length_SI "^3" 136 #define unit_invvisc_SI unit_length_SI " " unit_time_SI "/" unit_mass_SI 137 138 /* The routines below can be used for converting units from or to GROMACS 139 internal units. */ 140 enum 141 { 142 eg2cAngstrom, 143 eg2cNm, 144 eg2cBohr, 145 eg2cKcal_Mole, 146 eg2cHartree, 147 eg2cHartree_e, 148 eg2cAngstrom3, 149 eg2cCoulomb, 150 eg2cDebye, 151 eg2cElectron, 152 eg2cBuckingham, 153 eg2cNR 154 }; 155 156 /* Convert value x to GROMACS units. Energy -> Energy, Length -> Length etc. 157 The type of x is deduced from unit, 158 which should be taken from the enum above. */ 159 extern double convert2gmx(double x, int unit); 160 161 /* Convert value x from GROMACS units to the desired one. 162 The type of return value is deduced from unit, see above */ 163 extern double gmx2convert(double x, int unit); 164 165 /* Convert the string to one of the units supported. Returns -1 if not found. */ 166 extern int string2unit(char* string); 167 168 /* Convert the unit to a string. Return NULL when unit is out of range. */ 169 extern const char* unit2string(int unit); 170 171 #endif 172