celeritas::constants Namespace Reference

Mathematical, numerical, and physical constants. More...

Variables
constexpr real_type	e_electron = 1
	Special case for CLHEP: electron charged is unity by definition.
Physical constants with <em>exact</em> value as defined by SI
constexpr real_type	c_light = 299792458. * units::meter / units::second
constexpr real_type	h_planck = 6.62607015e-34 * units::joule * units::second
constexpr real_type	k_boltzmann = 1.380649e-23 * units::joule / units::kelvin
constexpr real_type	na_avogadro = 6.02214076e23
constexpr real_type	kcd_luminous = 683
Exact derivative constants
constexpr real_type	hbar_planck = h_planck / (2 * pi)
Experimental physical constants from CODATA 2018
constexpr real_type	a0_bohr = 5.29177210903e-11 * units::meter
constexpr real_type	alpha_fine_structure = 7.2973525693e-3
constexpr real_type	atomic_mass = 1.66053906660e-24 * units::gram
constexpr real_type	electron_mass = 9.1093837015e-28 * units::gram
constexpr real_type	proton_mass = 1.67262192369e-24 * units::gram
constexpr real_type	eps_electric = 8.8541878128e-12 * units::farad / units::meter
constexpr real_type	mu_magnetic
constexpr real_type	r_electron = 2.8179403262e-15 * units::meter
constexpr real_type	rinf_rydberg = 10973731.568160 / units::meter
constexpr real_type	eh_hartree = 4.3597447222071e-18 / units::meter
constexpr real_type	lambdabar_electron = 3.8615926796e-13 * units::meter
Other constants
constexpr real_type	stable_decay_constant = 0
Mathemetical constants (truncated)
constexpr real_type	pi = 3.14159265358979323846
constexpr real_type	euler = 2.71828182845904523536
constexpr real_type	sqrt_two = 1.41421356237309504880
constexpr real_type	sqrt_three = 1.73205080756887729353

Detailed Description

Mathematical, numerical, and physical constants.

Some of the physical constants listed here are exact numerical values: see the International System of Units, 9th ed. (2019), for definition of constants and how they relate to the different units.

Celeritas	CLHEP	Notes
a0_bohr	Bohr_radius	Bohr radius
alpha_fine_structure	fine_structure_const
atomic_mass	amu	Not the same as 1/avogadro
eps_electric	epsilon0	Vacuum permittivity
h_planck	h_Planck
k_boltzmann	k_Boltzmann
mu_magnetic	mu0	Vacuum permeability
na_avogadro	Avogadro	[1/mol]
r_electron	classic_electr_radius	Classical electron radius
kcd_luminous	[none]	Lumens per Watt
lambdabar_electron	electron_Compton_length	Reduced Compton wavelength
stable_decay_constant	[none]	Decay for a stable particle

In the CLHEP unit system, the value of the constant e_electron is defined to be 1 and coulomb is derivative from that. To avoid floating point arithmetic issues that would lead to the "units" and "constants" having different values for it, a special case redefines the value for CLHEP.

Some experimental physical constants are derived from the other physical constants, but for consistency and clarity they are presented numerically with the units provided in the CODATA 2018 dataset. The Constants.test.cc unit tests compare the numerical value against the derivative values inside the celeritas unit system. All experimental values include the final (ususally two) imprecise digits; their precision is usually on the order of \( 10^{-11} \).

Variable Documentation

mu_magnetic

constexpr real_type celeritas::constants::mu_magnetic

inlineconstexpr

Initial value:

= 1.25663706212e-6 * units::newton
                         / (units::ampere * units::ampere)