mirror of https://gitlab.com/QEF/q-e.git
155 lines
5.8 KiB
Fortran
155 lines
5.8 KiB
Fortran
!
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! Copyright (C) 2002-2006 Quantum ESPRESSO group
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! This file is distributed under the terms of the
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! GNU General Public License. See the file `License'
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! in the root directory of the present distribution,
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! or http://www.gnu.org/copyleft/gpl.txt .
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!
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!----------------------------------------------------------------------------
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MODULE constants
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!----------------------------------------------------------------------------
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!! The constants needed everywhere
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!
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USE kinds, ONLY : DP
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!
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IMPLICIT NONE
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!
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SAVE
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!
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! ... Mathematical constants
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!
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REAL(DP), PARAMETER :: pi = 3.14159265358979323846_DP
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REAL(DP), PARAMETER :: tpi = 2.0_DP * pi
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REAL(DP), PARAMETER :: fpi = 4.0_DP * pi
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REAL(DP), PARAMETER :: sqrtpi = 1.77245385090551602729_DP
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REAL(DP), PARAMETER :: sqrtpm1= 1.0_DP / sqrtpi
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REAL(DP), PARAMETER :: sqrt2 = 1.41421356237309504880_DP
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!
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! ... Physical constants, SI (NIST 2018)
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! http://physics.nist.gov/constants
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!
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REAL(DP), PARAMETER :: H_PLANCK_SI = 6.62607015E-34_DP ! J s
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REAL(DP), PARAMETER :: K_BOLTZMANN_SI = 1.380649E-23_DP ! J K^-1
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REAL(DP), PARAMETER :: ELECTRON_SI = 1.602176634E-19_DP ! C
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REAL(DP), PARAMETER :: ELECTRONVOLT_SI = 1.602176634E-19_DP ! J
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REAL(DP), PARAMETER :: ELECTRONMASS_SI = 9.1093837015E-31_DP ! Kg
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REAL(DP), PARAMETER :: HARTREE_SI = 4.3597447222071E-18_DP ! J
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REAL(DP), PARAMETER :: RYDBERG_SI = HARTREE_SI/2.0_DP ! J
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REAL(DP), PARAMETER :: BOHR_RADIUS_SI = 0.529177210903E-10_DP ! m
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REAL(DP), PARAMETER :: AMU_SI = 1.66053906660E-27_DP ! Kg
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REAL(DP), PARAMETER :: C_SI = 2.99792458E+8_DP ! m sec^-1
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REAL(DP), PARAMETER :: MUNOUGHT_SI = fpi*1.0E-7_DP ! N A^-2
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REAL(DP), PARAMETER :: EPSNOUGHT_SI = 1.0_DP / (MUNOUGHT_SI * &
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C_SI**2) ! F m^-1
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!
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! ... Physical constants, atomic units:
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! ... AU for "Hartree" atomic units (e = m = hbar = 1)
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! ... RY for "Rydberg" atomic units (e^2=2, m=1/2, hbar=1)
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!
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REAL(DP), PARAMETER :: K_BOLTZMANN_AU = K_BOLTZMANN_SI / HARTREE_SI
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REAL(DP), PARAMETER :: K_BOLTZMANN_RY = K_BOLTZMANN_SI / RYDBERG_SI
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!
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! ... Unit conversion factors: energy and masses
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!
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REAL(DP), PARAMETER :: AUTOEV = HARTREE_SI / ELECTRONVOLT_SI
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REAL(DP), PARAMETER :: RYTOEV = AUTOEV / 2.0_DP
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REAL(DP), PARAMETER :: AMU_AU = AMU_SI / ELECTRONMASS_SI
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REAL(DP), PARAMETER :: AMU_RY = AMU_AU / 2.0_DP
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!
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! ... Unit conversion factors: atomic unit of time, in s and ps
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!
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REAL(DP), PARAMETER :: AU_SEC = H_PLANCK_SI/tpi/HARTREE_SI
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REAL(DP), PARAMETER :: AU_PS = AU_SEC * 1.0E+12_DP
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!
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! ... Unit conversion factors: pressure (1 Pa = 1 J/m^3, 1GPa = 10 Kbar )
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!
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REAL(DP), PARAMETER :: AU_GPA = HARTREE_SI / BOHR_RADIUS_SI ** 3 &
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/ 1.0E+9_DP
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REAL(DP), PARAMETER :: RY_KBAR = 10.0_DP * AU_GPA / 2.0_DP
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!
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! ... Unit conversion factors: 1 debye = 10^-18 esu*cm
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! ... = 3.3356409519*10^-30 C*m
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! ... = 0.208194346 e*A
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! ... ( 1 esu = (0.1/c) Am, c=299792458 m/s)
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!
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REAL(DP), PARAMETER :: DEBYE_SI = 3.3356409519_DP * 1.0E-30_DP ! C*m
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REAL(DP), PARAMETER :: AU_DEBYE = ELECTRON_SI * BOHR_RADIUS_SI / &
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DEBYE_SI
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!
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REAL(DP), PARAMETER :: eV_to_kelvin = ELECTRONVOLT_SI / K_BOLTZMANN_SI
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REAL(DP), PARAMETER :: ry_to_kelvin = RYDBERG_SI / K_BOLTZMANN_SI
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!
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! .. Unit conversion factors: Energy to wavelength
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!
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REAL(DP), PARAMETER :: EVTONM = 1E+9_DP * H_PLANCK_SI * C_SI / &
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&ELECTRONVOLT_SI
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REAL(DP), PARAMETER :: RYTONM = 1E+9_DP * H_PLANCK_SI * C_SI / RYDBERG_SI
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!
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! Speed of light in atomic units
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!
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REAL(DP), PARAMETER :: C_AU = C_SI / BOHR_RADIUS_SI * AU_SEC
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!
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! ... zero up to a given accuracy
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!
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REAL(DP), PARAMETER :: eps4 = 1.0E-4_DP
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REAL(DP), PARAMETER :: eps6 = 1.0E-6_DP
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REAL(DP), PARAMETER :: eps8 = 1.0E-8_DP
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REAL(DP), PARAMETER :: eps12 = 1.0E-12_DP
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REAL(DP), PARAMETER :: eps14 = 1.0E-14_DP
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REAL(DP), PARAMETER :: eps16 = 1.0E-16_DP
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REAL(DP), PARAMETER :: eps24 = 1.0E-24_DP
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REAL(DP), PARAMETER :: eps32 = 1.0E-32_DP
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!
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REAL(DP), PARAMETER :: gsmall = 1.0E-12_DP
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!
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REAL(DP), PARAMETER :: e2 = 2.0_DP ! the square of the electron charge
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REAL(DP), PARAMETER :: degspin = 2.0_DP ! the number of spins per level
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!
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!---- COMPATIBIILITY
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!
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REAL(DP), PARAMETER :: BOHR_RADIUS_CM = BOHR_RADIUS_SI * 100.0_DP
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REAL(DP), PARAMETER :: BOHR_RADIUS_ANGS = BOHR_RADIUS_CM * 1.0E8_DP
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REAL(DP), PARAMETER :: ANGSTROM_AU = 1.0_DP/BOHR_RADIUS_ANGS
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REAL(DP), PARAMETER :: DIP_DEBYE = AU_DEBYE
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REAL(DP), PARAMETER :: AU_TERAHERTZ = AU_PS
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REAL(DP), PARAMETER :: AU_TO_OHMCMM1 = 46000.0_DP ! (ohm cm)^-1
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REAL(DP), PARAMETER :: RY_TO_THZ = 1.0_DP / AU_TERAHERTZ / FPI
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REAL(DP), PARAMETER :: RY_TO_GHZ = RY_TO_THZ*1000.0_DP
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REAL(DP), PARAMETER :: RY_TO_CMM1 = 1.E+10_DP * RY_TO_THZ / C_SI
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!
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REAL(DP), PARAMETER :: AVOGADRO = 6.02214076D+23
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END MODULE constants
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! perl script to create a program to list the available constants:
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! extract with: grep '^!XX!' constants.f90 | sed 's,!XX!,,' > mkconstlist.pl
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! then run: perl mkconstlist.pl constants.f90 > testme.f90
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! and compile and run: testme.f90
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!XX!#!/usr/bin/perl -w
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!XX!
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!XX!use strict;
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!XX!
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!XX!print <<EOF
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!XX!! list all available constants and derived values
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!XX!
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!XX!PROGRAM list_constants
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!XX!
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!XX! USE kinds, ONLY : DP
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!XX! USE constants
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!XX!
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!XX!EOF
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!XX!;
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!XX!
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!XX!while(<>) {
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!XX! if ( /REAL\s*\(DP\)\s*,\s*PARAMETER\s*::\s*([a-zA-Z_0-9]+)\s*=.*$/ ) {
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!XX! print " WRITE (*,'(A18,G24.17)') '$1:',$1\n";
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!XX! }
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!XX!}
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!XX!
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!XX!print <<EOF
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!XX!
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!XX!END PROGRAM list_constants
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!XX!EOF
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!XX!;
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!XX!
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