mirror of https://gitlab.com/QEF/q-e.git
180 lines
5.8 KiB
Fortran
180 lines
5.8 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 setlocq (xq, lloc, lmax, numeric, mesh, msh, rab, r, &
|
|
vloc_at, cc, alpc, nlc, nnl, zp, aps, alps, tpiba2, ngm, g, omega, &
|
|
vloc)
|
|
!----------------------------------------------------------------------
|
|
!
|
|
! This routine computes the Fourier transform of the local
|
|
! part of the pseudopotential in the q+G vectors.
|
|
! Two types of local potentials are allowed:
|
|
!
|
|
! a) The pseudopotential is in analytic form and its fourier
|
|
! transform is computed analytically
|
|
! b) The pseudopotential is in numeric form and its fourier
|
|
! transform is computed numerically
|
|
!
|
|
! The local pseudopotential of the US case is always in
|
|
! numerical form, expressed in Ry units.
|
|
!
|
|
! Last revision 5 oct. 1995 by Andrea Dal Corso
|
|
!
|
|
!
|
|
#include "f_defs.h"
|
|
USE kinds, only : DP
|
|
USE constants, ONLY : e2, fpi, pi
|
|
!
|
|
implicit none
|
|
!
|
|
! first the dummy variables
|
|
!
|
|
integer :: nlc, nnl, ngm, lloc, lmax, mesh, msh
|
|
! input: analytic, number of erf functions
|
|
! input: analytic, number of gaussian funct
|
|
! input: the number of G vectors
|
|
! input: the non local part which becomes l
|
|
! input: the maximum non local angular mome
|
|
! input: numeric, the dimensions of the mes
|
|
! input: mesh points for radial integration
|
|
|
|
real(kind=DP) :: xq (3), cc (2), alpc (2), alps (3, 0:3), aps (6, 0:3), &
|
|
zp, rab (mesh), r (mesh), vloc_at(mesh), tpiba2, omega, g (3, ngm), &
|
|
vloc (ngm)
|
|
! input: the q point
|
|
! input: analytic, c of the erf functions
|
|
! input: analytic, alpha of the erf
|
|
! input: analytic, alpha of the gaussians
|
|
! input: analytic, a and b of the gaussians
|
|
! input: valence pseudocharge
|
|
! input: numeric, the derivative of mesh po
|
|
! input: numeric, the mesh points
|
|
! input: numeric, the pseudo on the radial
|
|
! input: 2 pi / alat
|
|
! input: the volume of the unit cell
|
|
! input: the g vectors coordinates
|
|
! output: the fourier transform of the pote
|
|
logical :: numeric
|
|
! input: if true the pseudo is numeric
|
|
!
|
|
!
|
|
! and the local variables
|
|
!
|
|
real(kind=DP), parameter :: eps = 1.d-8
|
|
real(kind=DP) :: vlcp, vloc0, fac, den1, den2, g2a, g2a1, aux (mesh), &
|
|
aux1 (mesh), gx
|
|
! auxiliary variables
|
|
! gx = modulus of g vectors
|
|
real(kind=DP), external :: erf
|
|
! the erf function
|
|
integer :: i, ig, l, ipol, ir
|
|
! counters
|
|
!
|
|
if (.not.numeric) then
|
|
vloc (:) = 0.d0
|
|
!
|
|
! In this case the potential is given in analytic form
|
|
!
|
|
do ig = 1, ngm
|
|
g2a = (xq (1) + g (1, ig) ) **2 + (xq (2) + g (2, ig) ) **2 + &
|
|
(xq (3) + g (3, ig) ) **2
|
|
if (g2a < eps) then
|
|
do i = 1, nlc
|
|
vloc (ig) = vloc (ig) + cc (i) * tpiba2 * 0.25d0 / alpc (i)
|
|
enddo
|
|
else
|
|
do i = 1, nlc
|
|
den1 = 0.25d0 * tpiba2 / alpc (i)
|
|
vlcp = - cc (i) * exp ( - g2a * den1) / g2a
|
|
vloc (ig) = vloc (ig) + vlcp
|
|
enddo
|
|
endif
|
|
enddo
|
|
den1 = zp * e2 * fpi / tpiba2 / omega
|
|
vloc (:) = vloc(:) * den1
|
|
!
|
|
! Add the local part l=lloc term (only if l <= lmax)
|
|
!
|
|
l = lloc
|
|
|
|
if (l <= lmax) then
|
|
!
|
|
! and here all the other g components
|
|
!
|
|
do ig = 1, ngm
|
|
g2a = ( (xq (1) + g (1, ig) ) **2 + (xq (2) + g (2, ig) ) ** &
|
|
2 + (xq (3) + g (3, ig) ) **2)
|
|
if (g2a < eps) then
|
|
do i = 1, nnl
|
|
fac = (pi / alps (i, l) ) **1.5d0 * e2 / omega
|
|
den1 = aps (i + 3, l) / alps (i, l)
|
|
vloc (ig) = vloc (ig) + fac * (aps (i, l) + den1 * 1.5d0)
|
|
enddo
|
|
else
|
|
do i = 1, nnl
|
|
den1 = aps (i + 3, l) / alps (i, l)
|
|
den2 = 0.25d0 * tpiba2 / alps (i, l)
|
|
fac = (pi / alps (i, l) ) **1.5d0 * e2 / omega
|
|
g2a1 = g2a * den2
|
|
vlcp = fac * exp ( - g2a1) * (aps (i, l) + den1 * &
|
|
(1.5d0 - g2a1) )
|
|
vloc (ig) = vloc (ig) + vlcp
|
|
enddo
|
|
endif
|
|
enddo
|
|
endif
|
|
else
|
|
!
|
|
! Pseudopotentials in numerical form (Vnl(lloc) contain the local part)
|
|
! in order to perform the Fourier transform, a term erf(r)/r is
|
|
! subtracted in real space and added again in G space
|
|
!
|
|
!
|
|
! first the G=0 term
|
|
!
|
|
do ir = 1, msh
|
|
aux (ir) = r (ir) * (r (ir) * vloc_at (ir) + zp * e2)
|
|
enddo
|
|
call simpson (msh, aux, rab, vloc0)
|
|
!
|
|
! here the G<>0 terms, we first compute the part of the integrand func
|
|
! indipendent of |G| in real space
|
|
!
|
|
do ir = 1, msh
|
|
aux1 (ir) = r (ir) * vloc_at (ir) + zp * e2 * erf (r (ir) )
|
|
enddo
|
|
fac = zp * e2 / tpiba2
|
|
!
|
|
! and here we perform the integral, after multiplying for the |G|
|
|
! dependent part
|
|
!
|
|
do ig = 1, ngm
|
|
g2a = (xq (1) + g (1, ig) ) **2 + (xq (2) + g (2, ig) ) **2 + &
|
|
(xq (3) + g (3, ig) ) **2
|
|
if (g2a < eps) then
|
|
vloc (ig) = vloc0
|
|
else
|
|
gx = sqrt (g2a * tpiba2)
|
|
do ir = 1, msh
|
|
aux (ir) = aux1 (ir) * sin (gx * r (ir) ) / gx
|
|
enddo
|
|
call simpson (msh, aux, rab, vlcp)
|
|
!
|
|
! here we add the analytic fourier transform of the erf function
|
|
!
|
|
vlcp = vlcp - fac * exp ( - g2a * tpiba2 * 0.25d0) / g2a
|
|
vloc (ig) = vlcp
|
|
endif
|
|
enddo
|
|
|
|
vloc(:) = vloc(:) * fpi / omega
|
|
endif
|
|
return
|
|
end subroutine setlocq
|