Description of the library

The TFEL/PhysicalConstants library is header-only which provides:

• A template class called PhysicalConstants in the namespace tfel. This class defined a constexpr static data member per physical constant. This class has two template parameters:
  • NumericType: which is the floatting point number type to be used to define the physical constants.
  • use_quantities: which states if quantities (i.e. numbers with units) shall be used. to be used to define the physical constants.
• A set of template constexpr inline variables defined in the namespace tfel::constants. Those variables have the same template parameters than the PhysicalConstants class

The values of the physical constants are extracted from: http://physics.nist.gov/cuu/Constants/index.html

The values of the physical constants depend on the compatibility modes: those of the current version of TFEL are those exposed by the names without suffix, whereas those of the next major version are those of the tfel::future and tfel::constants::future namespaces, as described in the page devoted to compatibility modes in the TFEL libraries.

Bindings

Fortran bindings

A include file named TFELPHYSICALCONSTANTS.INC is provided for fortran77. This include declares the physical constants as real64 parameters.

A module named TFEL_PHYSICAL_CONSTANTS is provided for fortran95. This module exposes the physical constants as real64 parameters.

The Fortran bindings are not versioned: they expose the values of the next major version of TFEL.

Python bindings

The tfel module exposes the class PhysicalConstants which declares the physical constants as read-only attributes. The constants of a given compatibility mode are exposed by a submodule of the same name.

Physical constants

• AtomicMassConstant (mu, \(kg\)): Atomic mass constant
• AvogadroConstant (Na, \(mol^{-1}\)): Avogadro constant
• BoltzmannConstant (kb, \(J.K^{-1}\)): Boltzmann constant
• ConductanceQuantum (G0, \(S\)): Conductance quantum
• ElectricConstant (e0, \(F.m^{-1}\)): Electric constant
• ElectronMass (me, \(kg\)): Electron mass
• ElectronVolt (eV, \(J\)): Electron volt
• ElementaryCharge (e, \(C\)): Elementary charge
• FaradayConstant (F, \(C.mol^{-1}\)): Faraday constant
• FineStructureConstant (a): Fine-structure constant
• MolarGasConstant (R, \(J.mol^{-1}.K^{-1}\)): Molar gas constant
• StefanBoltzmannConstant (s, \(W.m^{-2}.K^{-4}\)): Stefan-Boltzmann constant