rotex__constants.f Source File

! ================================================================================================================================ !
module rotex__constants
  !! Contains most (but not all) defined constants used throughout the code.

  use iso_fortran_env, only: IOSTAT_END
  use rotex__kinds,    only: dp

  implicit none

  private

  public :: IOSTAT_END

  integer, parameter, public :: IOSTAT_OK = 0
  integer, parameter, public :: IQ_DEFAULT = 4 ! default Coulomb f,g normalization
  integer, parameter, public :: DEFAULT_INT = -409

  real(dp), parameter, public :: CB_MINT_IMAG_THRESH = 1e-8_dp
    !! Warn user if CB cross section M integrals have imaginary components
    !! larger than this value (they should be real). The code will try to skip such values.
  real(dp), parameter, public :: HYPGEO_ABC_THRESHOLD = 160._dp
    !! Threshold for warning the user about large values of a,b,c in
    !! ₂F₁(a,b;c;z)
  real(dp), parameter, public :: ahalf = 0.5_dp
  real(dp), parameter, public :: zero  = 0._dp
  real(dp), parameter, public :: one   = 1._dp
  real(dp), parameter, public :: two   = 2._dp
  real(dp), parameter, public :: three = 3._dp
  real(dp), parameter, public :: four  = 4._dp
  real(dp), parameter, public :: pi    = atan(1._dp) * 4._dp
    !! π
  real(dp), parameter, public :: invc = 1._dp/137.035999177_dp
    !! 1/c, where c is the speed of light in atomic units. This is equal to the fine structure constant α.
  real(dp), parameter, public :: macheps_dp = epsilon(one)
  real(dp), parameter, public :: rho = 0.8_dp
  real(dp), parameter, public :: euler_mascheroni = 0.57721566490153286060651209008240243104215933593992_dp
    !! the Euler Mascheroni constant. The difference between the harmonic series and the natural logarithm
  real(dp), parameter, public :: au2ryd = 2._dp
    !! Hartree -> Rydberg
  real(dp), parameter, public :: au2ev = 27.2113834e0_dp
    !! Hartree -> eV
  real(dp), parameter, public :: au2ang = 0.5291772083_dp
    !! Bohr -> Ångstrom
  real(dp), parameter, public :: au2cm = au2ang * 1e-8_dp
    !! Bohr -> cm
  real(dp), parameter, public :: au2invcm = 219474.6313710e0_dp
    !! multiplication factor to convert atomic units of energy (hartree) to wavenumbers (inverse centimeters)
  real(dp), parameter, public :: au2sec = 2.4188843e-17_dp
    !! multiplication factor to convert atomic units of time (hbar / hartree) to seconds
  real(dp), parameter, public :: au2deb = 2.5417462762781615_dp
    !! atomic units (electric dipole) -> Debye

  complex(dp), parameter, public :: im = (zero, one)
    !! the square root of -1

  character(1), parameter, public :: CHAR_CR = achar(13)
  character(1), parameter, public :: DEFAULT_CHAR1 = "x"
  character(7), parameter, public :: UKRMOLX = 'ukrmol+'
  character(7), parameter, public :: MQDTR2K = 'mqdtr2k'
  character(7), parameter, public :: spinmult_names(5) = &
    [ 'singlet', 'doublet', 'triplet', 'quartet', 'quintet' ]

! ================================================================================================================================ !
end module rotex__constants
! ================================================================================================================================ !