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