mirror of https://gitlab.com/QEF/q-e.git
96 lines
2.9 KiB
Fortran
96 lines
2.9 KiB
Fortran
!
|
|
! Copyright (C) 2001 PWSCF 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 .
|
|
!
|
|
!
|
|
!-----------------------------------------------------------------------
|
|
subroutine deriv_drhoc (ngl, gl, omega, tpiba2, numeric, a_nlcc, &
|
|
b_nlcc, alpha_nlcc, mesh, r, rab, rhoc, drhocg)
|
|
!-----------------------------------------------------------------------
|
|
#include "machine.h"
|
|
use parameters
|
|
implicit none
|
|
!
|
|
! first the dummy variables
|
|
!
|
|
|
|
integer :: ngl, mesh
|
|
! input: the number of g shell
|
|
! input: the number of radial mesh points
|
|
|
|
real(kind=DP) :: gl (ngl), r (mesh), rab (mesh), rhoc (mesh), omega, &
|
|
tpiba2, a_nlcc, b_nlcc, alpha_nlcc, drhocg (ngl)
|
|
! input: the number of G shells
|
|
! input: the radial mesh
|
|
! input: the derivative of theradial mesh
|
|
! input: the radial core charge
|
|
! input: the volume of the unit cell
|
|
! input: 2 times pi / alat
|
|
! input: the a_c of the analitycal form
|
|
! input: the b_c of the analitical form
|
|
! input: the alpha of the analytical form
|
|
! output: fourier transform of d Rho_c/dG
|
|
logical :: numeric
|
|
! input: if true the charge is in numeric
|
|
!
|
|
! two parameters
|
|
!
|
|
real(kind=DP) :: pi, fpi
|
|
parameter (pi = 3.14159265358979d0, fpi = 4.d0 * pi)
|
|
!
|
|
! here the local variables
|
|
!
|
|
|
|
real(kind=DP) :: gx, g2a, rhocg1
|
|
real(kind=DP), allocatable :: aux (:)
|
|
! the modulus of g for a given shell
|
|
! the argument of the exponential
|
|
! the fourier transform
|
|
! auxiliary memory for integration
|
|
|
|
integer :: igl, igl0 ,i
|
|
! counter on g shells
|
|
! lower limit for loop on ngl
|
|
|
|
!
|
|
! G=0 term
|
|
!
|
|
if (gl (1) .lt.1.0e-8) then
|
|
drhocg (1) = 0.0
|
|
igl0 = 2
|
|
else
|
|
igl0 = 1
|
|
|
|
endif
|
|
|
|
if (numeric) then
|
|
|
|
allocate (aux( mesh))
|
|
do igl = igl0, ngl
|
|
gx = sqrt (gl (igl) * tpiba2)
|
|
do i = 1, mesh
|
|
aux (i) = r (i) * rhoc (i) * (r (i) * cos (gx * r (i) ) &
|
|
/ gx - sin (gx * r (i) ) / gx**2)
|
|
enddo
|
|
call simpson (mesh, aux, rab, rhocg1)
|
|
drhocg (igl) = fpi / omega * rhocg1
|
|
|
|
enddo
|
|
|
|
deallocate (aux)
|
|
else
|
|
do igl = igl0, ngl
|
|
g2a = gl (igl) * tpiba2 / 4.0 / alpha_nlcc
|
|
drhocg (igl) = - (pi / alpha_nlcc) **1.5 * exp ( - g2a) &
|
|
* (a_nlcc + b_nlcc / alpha_nlcc * (2.5 - g2a) ) * sqrt (gl ( &
|
|
igl) * tpiba2) / 2.0 / alpha_nlcc / omega
|
|
enddo
|
|
|
|
endif
|
|
return
|
|
end subroutine deriv_drhoc
|
|
|