mirror of https://gitlab.com/QEF/q-e.git
119 lines
3.3 KiB
Fortran
119 lines
3.3 KiB
Fortran
!
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! Copyright (C) 2001-2008 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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!-----------------------------------------------------------------------
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subroutine compute_drhous (drhous, dbecsum, wgg, becq, alpq)
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!-----------------------------------------------------------------------
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!
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! This routine computes the part of the change of the charge density
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! which is due to the orthogonalization constraint on wavefunctions
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!
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!
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USE kinds, ONLY : DP
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USE ions_base, ONLY : nat
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USE wavefunctions, ONLY: evc
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USE buffers, ONLY : get_buffer
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USE uspp, ONLY : okvan, nkb, vkb
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USE uspp_param, ONLY : nhm
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USE lsda_mod, ONLY : lsda, nspin, current_spin, isk
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USE klist, ONLY : xk, wk, ngk, igk_k
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USE fft_base, ONLY: dffts, dfftp
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USE fft_interfaces, ONLY: invfft
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USE wvfct, ONLY : nbnd
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USE qpoint, ONLY : nksq, ikks, ikqs
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USE eqv, ONLY : evq
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USE control_lr, ONLY : lgamma
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USE units_ph, ONLY : iuwfc, lrwfc
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USE becmod, ONLY : bec_type
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implicit none
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!
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! the dummy variables
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!
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complex(DP) :: dbecsum (nhm * (nhm + 1) / 2, nat, nspin, 3 * nat) &
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, drhous (dfftp%nnr, nspin, 3 * nat)
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!output:the derivative of becsum
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! output: add the orthogonality term
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type (bec_type) :: becq(nksq), & ! (nkb, nbnd)
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alpq (3, nksq)
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! input: the becp with psi_{k+q}
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! input: the alphap with psi_{k+q}
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real(DP) :: wgg (nbnd, nbnd, nksq)
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! input: the weights
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integer :: npw, npwq, ik, ikq, ikk, ig, nu_i, ibnd, ios
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! counter on k points
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! the point k+q
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! record for wfcs at k point
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! counter on spin
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! counter on g vectors
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! counter on modes
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! counter on the bands
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! integer variable for I/O control
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real(DP) :: weight
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! the weight of the k point
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complex(DP), allocatable :: evcr (:,:)
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! the wavefunctions in real space
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if (.not.okvan) return
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call start_clock ('com_drhous')
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allocate (evcr( dffts%nnr, nbnd))
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!
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drhous(:,:,:) = (0.d0, 0.d0)
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dbecsum (:,:,:,:) = (0.d0, 0.d0)
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do ik = 1, nksq
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ikk = ikks(ik)
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ikq = ikqs(ik)
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npw = ngk(ikk)
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npwq= ngk(ikq)
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weight = wk (ikk)
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if (lsda) current_spin = isk (ikk)
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!
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! For each k point we construct the beta functions
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!
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call init_us_2 (npwq, igk_k(1,ikq), xk (1, ikq), vkb)
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!
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! Read the wavefunctions at k and transform to real space
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!
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call get_buffer (evc, lrwfc, iuwfc, ikk)
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evcr(:,:) = (0.d0, 0.d0)
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do ibnd = 1, nbnd
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do ig = 1, npw
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evcr (dffts%nl (igk_k(ig,ikk) ), ibnd) = evc (ig, ibnd)
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enddo
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CALL invfft ('Wave', evcr (:, ibnd), dffts)
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enddo
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!
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! Read the wavefunctions at k+q
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!
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if (.not.lgamma.and.nksq.gt.1) call get_buffer (evq, lrwfc, iuwfc, ikq)
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!
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! And compute the contribution of this k point to the change of
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! the charge density
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!
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do nu_i = 1, 3 * nat
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call incdrhous (drhous (1, current_spin, nu_i), weight, ik, &
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dbecsum (1, 1, current_spin, nu_i), evcr, wgg, becq, alpq, nu_i)
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enddo
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enddo
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deallocate(evcr)
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call stop_clock ('com_drhous')
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return
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end subroutine compute_drhous
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