units.hpp

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/*
** This file is part of eOn.
**
** SPDX-License-Identifier: BSD-3-Clause
**
** Copyright (c) 2010--present, eOn Development Team
** All rights reserved.
**
** Repo:
** https://github.com/TheochemUI/eOn
*/
#pragma once

#define FORCEFIELDS_UNIT_SYSTEM_SI_MKSA 0
#define FORCEFIELDS_UNIT_SYSTEM_METRE_KILOGRAMME_PER_MOL_SECOND_AMPERE_PER_MOL 1
#define FORCEFIELDS_UNIT_SYSTEM_ANGSTROM_KILOGRAMME_PER_MOL_FEMTOSECOND_AMPERE_PER_MOL \
  2

#define FORCEFIELDS_UNIT_SYSTEM_ANGSTROM_GRAMME_PER_MOL_FEMTOSECOND_ECHARGE 3
#define FORCEFIELDS_UNIT_SYSTEM_ELECTRONVOLT_ANGSTROM_FEMTOSECOND_ECHARGE 4
#define FORCEFIELDS_UNIT_SYSTEM_KILOCALORY_PER_MOL_ANGSTROM_FEMTOSECOND_ECHARGE \
  5

#undef FORCEFIELDS_UNIT_SYSTEM_HPP
#define FORCEFIELDS_UNIT_SYSTEM_HPP                                            \
  FORCEFIELDS_UNIT_SYSTEM_ELECTRONVOLT_ANGSTROM_FEMTOSECOND_ECHARGE
namespace forcefields {
namespace unit_system {
// Some physical constants expressed in SI unit. Source for constants:
// http://physics.nist.gov/cuu/Constants/index.html
const double R_gas = 8.314472;            // J/mol/K
const double k_boltzmann = 1.3806505e-23; // J/K
const double Na_avogadro = 6.0221415e23;  // mol^-1
const double /* 1 */ calory = 4.1868;     // J
const double e_charge = 1.60217653e-19;   // C
const double /* 1 */ debye =
    3.33564e-30; // C m
const double one_over_4_pi_epsilon0 =
    8.98755178495272255e+09; // SI
const double sqrt_one_over_4_pi_epsilon0 = 9.48026992492973368e+04; // SI
 
// System independent units
const double pi = 3.14159265358979312;
const double MOL = Na_avogadro;
const double DEGREE = pi / 180; // rad
 
#if FORCEFIELDS_UNIT_SYSTEM_HPP == FORCEFIELDS_UNIT_SYSTEM_SI_MKSA
const char LENGTH[] = "m";
const char MASS[] = "kg";
const char TIME[] = "s";
const char CURRENT[] = "A"; // Ampere
const char VELOCITY[] = "m/s";
const char ACCELERATION[] = "m s^-2";
const char FORCE[] = "N";
const char ENERGY[] = "J";
const char PRESSURE[] = "Pa";
const char CHARGE[] = "C";
 
// Main SI units Converters
const double /* 1 */ METRE = 1.0;  // m
const double /* 1 */ KG = 1.0;     // kg
const double /* 1 */ SECOND = 1.0; // s
const double /* 1 */ AMPERE = 1.0; // A
#elif FORCEFIELDS_UNIT_SYSTEM_HPP ==                                           \
    FORCEFIELDS_UNIT_SYSTEM_METRE_KILOGRAMME_PER_MOL_SECOND_AMPERE_PER_MOL
const char LENGTH[] = "m";
const char MASS[] = "kg/mol";
const char TIME[] = "s";
const char CURRENT[] = "A/mol";
const char VELOCITY[] = "m/s";
const char ACCELERATION[] = "m s^-2";
const char FORCE[] = "N/mol";
const char ENERGY[] = "J/mol";
const char PRESSURE[] = "Pa/mol";
const char CHARGE[] = "C/mol";
 
// Main SI units Converters
const double /* 1 */ METRE = 1.0;  // m
const double /* 1 */ KG = MOL;     // kg/mol
const double /* 1 */ SECOND = 1.0; // s
const double /* 1 */ AMPERE = MOL; // A/mol
#elif FORCEFIELDS_UNIT_SYSTEM_HPP ==                                           \
    FORCEFIELDS_UNIT_SYSTEM_ANGSTROM_KILOGRAMME_PER_MOL_FEMTOSECOND_AMPERE_PER_MOL
const char LENGTH[] = "Angstrom";
const char MASS[] = "kg/mol";
const char TIME[] = "fs";
const char CURRENT[] = "A/mol";
const char VELOCITY[] = "Angstrom/fs";
const char ACCELERATION[] = "Angstrom fs^-2";
const char FORCE[] = "1e30 N/mol";
const char ENERGY[] = "1e20 J/mol";
const char PRESSURE[] = "1e50 Pa/mol";
const char CHARGE[] = "C/mol";
 
// Main SI units Converters
const double /* 1 */ METRE = 1e10;  // m
const double /* 1 */ KG = MOL;      // kg/mol
const double /* 1 */ SECOND = 1e15; // s
const double /* 1 */ AMPERE = MOL;  // A/mol
#elif FORCEFIELDS_UNIT_SYSTEM_HPP ==                                           \
    FORCEFIELDS_UNIT_SYSTEM_ANGSTROM_GRAMME_PER_MOL_FEMTOSECOND_ECHARGE
const char LENGTH[] = "Angstrom";
const char MASS[] = "g/mol";
const char TIME[] = "fs";
const char CURRENT[] = "e/fs";
const char VELOCITY[] = "Angstrom/fs";
const char ACCELERATION[] = "Angstrom fs^-2";
const char FORCE[] = "1e17 J / Angstrom";
const char ENERGY[] = "1e17 J";
const char PRESSURE[] = "1e17 J Angstrom^-3";
const char CHARGE[] = "e";
 
// Main SI units Converters
const double /* 1 */ METRE = 1e10;    // Angstrom
const double /* 1 */ KG = 1000 * MOL; // g/mol
const double /* 1 */ SECOND =
    1e15; // fs
          // 1 e/fs= e_charge C / 1e-15 s=e_charge*1e15 A
const double /* 1 */ AMPERE = 1e-15 / e_charge; // e/fs
#elif FORCEFIELDS_UNIT_SYSTEM_HPP ==                                           \
    FORCEFIELDS_UNIT_SYSTEM_ELECTRONVOLT_ANGSTROM_FEMTOSECOND_ECHARGE
const char LENGTH[] = "A"; // Angstrom
const char TIME[] = "fs";  // second
const char MASS[] = "eV A^-2 fs^2";
const char CURRENT[] = "e/fs";
const char VELOCITY[] = "A fs^-1";
const char ACCELERATION[] = "A fs^-2";
const char FORCE[] = "eV/A";
const char ENERGY[] = "eV"; // electron volt
const char PRESSURE[] = "eV A^-3";
const char CHARGE[] = "(eV A)^(-1/2)";
 
// Main SI units Converters
const double /* 1 */ METRE = 1e10;         // Angstrom
                                           //  1 J = 1 kg m^2 s^-2
                                           //  e_charge C V = e_charge J = 1 eV
const double /* 1 */ KG = 1e10 / e_charge; // eV Angstrom^-2 fs^2
const double /* 1 */ SECOND = 1e15;        // fs
const double /* 1 */ AMPERE = 1e-15 / e_charge; // e/fs
#elif FORCEFIELDS_UNIT_SYSTEM_HPP ==                                           \
    FORCEFIELDS_UNIT_SYSTEM_KILOCALORY_PER_MOL_ANGSTROM_FEMTOSECOND_ECHARGE
const char LENGTH[] = "A"; // Angstrom
const char TIME[] = "fs";  // second
const char MASS[] = "kcal/mol A^-2 fs^2";
const char CURRENT[] = "e/fs";
const char VELOCITY[] = "A fs^-1";
const char ACCELERATION[] = "A fs^-2";
const char FORCE[] = "kcal mol A^-1";
const char ENERGY[] = "kcal/mol"; // electron volt
const char PRESSURE[] = "kcal/mol A^-3";
const char CHARGE[] = "(kcal/mol A)^(-1/2)";
 
// Main SI units Converters
const double /* 1 */ METRE = 1e10; // Angstrom
                                   //  1 J = 1 kg m^2 s^-2
                                   //  e_charge C V = e_charge J = 1 eV
const double /* 1 */ KG =
    Na_avogadro * 1e7 / calory;                 // kcal/mol Angstrom^-2 fs^2
const double /* 1 */ SECOND = 1e15;             // fs
const double /* 1 */ AMPERE = 1e-15 / e_charge; // e/fs
#endif
const char *const TEMPERATURE = ENERGY;
// SI Units
const double METRE_PER_SECOND = METRE / SECOND;
const double METRE_PER_SECOND2 = METRE_PER_SECOND / SECOND;
const double /* 1 */ NEWTON = KG * METRE_PER_SECOND2;
const double /* 1 */ JOULE = NEWTON * METRE;
const double /* 1 */ COULOMB = AMPERE * SECOND;
const double WATT = JOULE / SECOND;
const double VOLT = WATT / AMPERE;
const double /* 1 */ KELVIN = k_boltzmann * JOULE;
// SI Prefix
const double /* 1 */ KILO = 1e3;
const double NANO = 1e-9;
const double FEMTO = 1e-15;
// Derived SI units
const double NM = NANO * METRE;
const double GRAM = KG / KILO;
const double /* 1 */ GRAM_PER_MOL = GRAM / MOL;
const double /* 1 */ G_PER_MOL = GRAM_PER_MOL;
const double /* 1 */ KJ_PER_MOL = KILO * JOULE / MOL;
const double /* 1 */ KJ = KILO * JOULE;
const double FS = FEMTO * SECOND;
// Common non SI Units
const double /* 1 */ ANGSTROM = 1e-10 * METRE;
const double /* 1 */ ANGSTROM2 = ANGSTROM * ANGSTROM;
const double /* 1 */ ANGSTROM3 = ANGSTROM * ANGSTROM * ANGSTROM;
const double ECHARGE = e_charge * COULOMB;
const double EV = ECHARGE * VOLT;
// Deprecated units
const double /* 1 */ CALORY = calory * JOULE;
const double /* 1 */ KCAL_PER_MOL = KILO * CALORY / MOL;
// Atomic Units
const double BOHR = 5.291772108e-11 * METRE;
const double HARTREE = 4.35974417e-18 * JOULE;
// CGS units
const double ERGS = 1e-7 * JOULE;
// Constants
const double ONE_OVER_4_PI_EPSILON0 =
    one_over_4_pi_epsilon0 * METRE * JOULE / COULOMB / COULOMB;
} // namespace unit_system
} // namespace forcefields