mirror of https://gitlab.com/QEF/q-e.git
74 lines
1.9 KiB
Fortran
74 lines
1.9 KiB
Fortran
!
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! Copyright (C) 2001-2007 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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subroutine deriv_drhoc (ngl, gl, omega, tpiba2, 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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USE constants, ONLY : pi, fpi
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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), intent(in) :: gl (ngl), r (mesh), rab (mesh), rhoc (mesh), &
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omega, tpiba2
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real(DP), intent(out) :: 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 the radial 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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! output: fourier transform of d Rho_c/dG
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!
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! here the local variables
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!
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real(DP) :: gx, rhocg1
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! the modulus of g for a given shell
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! the fourier transform
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real(DP), allocatable :: aux (:)
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! auxiliary memory for integration
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integer :: ir, igl, igl0
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! counter on radial mesh points
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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) < 1.0d-8) then
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drhocg (1) = 0.0d0
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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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!
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! G <> 0 term
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!
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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 ir = 1, mesh
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aux (ir) = r (ir) * rhoc (ir) * (r (ir) * cos (gx * r (ir) ) &
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/ gx - sin (gx * r (ir) ) / 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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return
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end subroutine deriv_drhoc
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