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!
! Copyright (C) 2002-2006 Quantum ESPRESSO group
! This file is distributed under the terms of the
! GNU General Public License. See the file `License'
! in the root directory of the present distribution,
! or http://www.gnu.org/copyleft/gpl.txt .
!
!----------------------------------------------------------------------------
MODULE constants
!----------------------------------------------------------------------------
!
USE kinds, ONLY : DP
!
! ... The constants needed everywhere
!
IMPLICIT NONE
!
SAVE
!
! ... Mathematical constants
!
REAL(DP), PARAMETER :: pi = 3.14159265358979323846_DP
REAL(DP), PARAMETER :: tpi = 2.0_DP * pi
REAL(DP), PARAMETER :: fpi = 4.0_DP * pi
REAL(DP), PARAMETER :: sqrtpi = 1.77245385090551602729_DP
REAL(DP), PARAMETER :: sqrtpm1= 1.0_DP / sqrtpi
REAL(DP), PARAMETER :: sqrt2 = 1.41421356237309504880_DP
!
! ... Physical constants, SI (NIST CODATA 2006), Web Version 5.1
! http://physics.nist.gov/constants
REAL(DP), PARAMETER :: H_PLANCK_SI = 6.62606896E-34_DP ! J s
REAL(DP), PARAMETER :: K_BOLTZMANN_SI = 1.3806504E-23_DP ! J K^-1
REAL(DP), PARAMETER :: ELECTRON_SI = 1.602176487E-19_DP ! C
REAL(DP), PARAMETER :: ELECTRONVOLT_SI = 1.602176487E-19_DP ! J
REAL(DP), PARAMETER :: ELECTRONMASS_SI = 9.10938215E-31_DP ! Kg
REAL(DP), PARAMETER :: HARTREE_SI = 4.35974394E-18_DP ! J
REAL(DP), PARAMETER :: RYDBERG_SI = HARTREE_SI/2.0_DP ! J
REAL(DP), PARAMETER :: BOHR_RADIUS_SI = 0.52917720859E-10_DP ! m
REAL(DP), PARAMETER :: AMU_SI = 1.660538782E-27_DP ! Kg
REAL(DP), PARAMETER :: C_SI = 2.99792458E+8_DP ! m sec^-1
REAL(DP), PARAMETER :: MUNOUGHT_SI = fpi*1.0E-7_DP ! N A^-2
REAL(DP), PARAMETER :: EPSNOUGHT_SI = 1.0_DP / (MUNOUGHT_SI * &
C_SI**2) ! F m^-1
!
! ... Physical constants, atomic units:
! ... AU for "Hartree" atomic units (e = m = hbar = 1)
! ... RY for "Rydberg" atomic units (e^2=2, m=1/2, hbar=1)
!
REAL(DP), PARAMETER :: K_BOLTZMANN_AU = K_BOLTZMANN_SI / HARTREE_SI
REAL(DP), PARAMETER :: K_BOLTZMANN_RY = K_BOLTZMANN_SI / RYDBERG_SI
!
! ... Unit conversion factors: energy and masses
!
REAL(DP), PARAMETER :: AUTOEV = HARTREE_SI / ELECTRONVOLT_SI
REAL(DP), PARAMETER :: RYTOEV = AUTOEV / 2.0_DP
REAL(DP), PARAMETER :: AMU_AU = AMU_SI / ELECTRONMASS_SI
REAL(DP), PARAMETER :: AMU_RY = AMU_AU / 2.0_DP
!
! ... Unit conversion factors: atomic unit of time, in s and ps
!
REAL(DP), PARAMETER :: AU_SEC = H_PLANCK_SI/tpi/HARTREE_SI
REAL(DP), PARAMETER :: AU_PS = AU_SEC * 1.0E+12_DP
!
! ... Unit conversion factors: pressure (1 Pa = 1 J/m^3, 1GPa = 10 Kbar )
!
REAL(DP), PARAMETER :: AU_GPA = HARTREE_SI / BOHR_RADIUS_SI ** 3 &
/ 1.0E+9_DP
REAL(DP), PARAMETER :: RY_KBAR = 10.0_DP * AU_GPA / 2.0_DP
!
! ... Unit conversion factors: 1 debye = 10^-18 esu*cm
! ... = 3.3356409519*10^-30 C*m
! ... = 0.208194346 e*A
! ... ( 1 esu = (0.1/c) Am, c=299792458 m/s)
!
REAL(DP), PARAMETER :: DEBYE_SI = 3.3356409519_DP * 1.0E-30_DP ! C*m
REAL(DP), PARAMETER :: AU_DEBYE = ELECTRON_SI * BOHR_RADIUS_SI / &
DEBYE_SI
!
REAL(DP), PARAMETER :: eV_to_kelvin = ELECTRONVOLT_SI / K_BOLTZMANN_SI
REAL(DP), PARAMETER :: ry_to_kelvin = RYDBERG_SI / K_BOLTZMANN_SI
!
! .. Unit conversion factors: Energy to wavelength
!
REAL(DP), PARAMETER :: EVTONM = 1E+9_DP * H_PLANCK_SI * C_SI / &
&ELECTRONVOLT_SI
REAL(DP), PARAMETER :: RYTONM = 1E+9_DP * H_PLANCK_SI * C_SI / RYDBERG_SI
!
! Speed of light in atomic units
!
REAL(DP), PARAMETER :: C_AU = C_SI / BOHR_RADIUS_SI * AU_SEC
!
! ... zero up to a given accuracy
!
REAL(DP), PARAMETER :: eps4 = 1.0E-4_DP
REAL(DP), PARAMETER :: eps6 = 1.0E-6_DP
REAL(DP), PARAMETER :: eps8 = 1.0E-8_DP
REAL(DP), PARAMETER :: eps12 = 1.0E-12_DP
REAL(DP), PARAMETER :: eps14 = 1.0E-14_DP
REAL(DP), PARAMETER :: eps16 = 1.0E-16_DP
REAL(DP), PARAMETER :: eps24 = 1.0E-24_DP
REAL(DP), PARAMETER :: eps32 = 1.0E-32_DP
!
REAL(DP), PARAMETER :: gsmall = 1.0E-12_DP
!
REAL(DP), PARAMETER :: e2 = 2.0_DP ! the square of the electron charge
REAL(DP), PARAMETER :: degspin = 2.0_DP ! the number of spins per level
!
!!!!!! COMPATIBIILITY
!
REAL(DP), PARAMETER :: BOHR_RADIUS_CM = BOHR_RADIUS_SI * 100.0_DP
REAL(DP), PARAMETER :: BOHR_RADIUS_ANGS = BOHR_RADIUS_CM * 1.0E8_DP
REAL(DP), PARAMETER :: ANGSTROM_AU = 1.0_DP/BOHR_RADIUS_ANGS
REAL(DP), PARAMETER :: DIP_DEBYE = AU_DEBYE
REAL(DP), PARAMETER :: AU_TERAHERTZ = AU_PS
REAL(DP), PARAMETER :: AU_TO_OHMCMM1 = 46000.0_DP ! (ohm cm)^-1
REAL(DP), PARAMETER :: RY_TO_THZ = 1.0_DP / AU_TERAHERTZ / FPI
REAL(DP), PARAMETER :: RY_TO_GHZ = RY_TO_THZ*1000.0_DP
REAL(DP), PARAMETER :: RY_TO_CMM1 = 1.E+10_DP * RY_TO_THZ / C_SI
!
END MODULE constants
! perl script to create a program to list the available constants:
! extract with: grep '^!XX!' constants.f90 | sed 's,!XX!,,' > mkconstlist.pl
! then run: perl mkconstlist.pl constants.f90 > testme.f90
! and compile and run: testme.f90
!XX!#!/usr/bin/perl -w
!XX!
!XX!use strict;
!XX!
!XX!print <<EOF
!XX!! list all available constants and derived values
!XX!
!XX!PROGRAM list_constants
!XX!
!XX! USE kinds, ONLY : DP
!XX! USE constants
!XX!
!XX!EOF
!XX!;
!XX!
!XX!while(<>) {
!XX! if ( /REAL\s*\(DP\)\s*,\s*PARAMETER\s*::\s*([a-zA-Z_0-9]+)\s*=.*$/ ) {
!XX! print " WRITE (*,'(A18,G24.17)') '$1:',$1\n";
!XX! }
!XX!}
!XX!
!XX!print <<EOF
!XX!
!XX!END PROGRAM list_constants
!XX!EOF
!XX!;
!XX!
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