mirror of https://gitlab.com/QEF/q-e.git
100 lines
2.9 KiB
Fortran
100 lines
2.9 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 compute_becalp (becq, alpq)
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!---------------------------------------------------------------------
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!
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! This routine is used only at finite q and in this case
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! computes the scalar product of vkb and psi_{k+q}, and of
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! the derivative of vkb and psi_{k+q}. Eq. B8 and B10 (at k+q)
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! of PRB 64 235118 (2001).
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!
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USE kinds, only : DP
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USE cell_base, ONLY : tpiba
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USE klist, ONLY : xk
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USE gvect, ONLY : g
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USE becmod, ONLY: calbec, bec_type
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USE uspp, ONLY: nkb, vkb
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USE noncollin_module, ONLY : noncolin, npol
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USE io_files, ONLY: iunigk
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USE wvfct, ONLY : nbnd, npw, npwx, igk
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USE paw_variables, ONLY : okpaw
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USE control_ph, ONLY : lgamma, rec_code_read
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USE eqv, ONLY : evq
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USE units_ph, ONLY : lrwfc, iuwfc
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USE qpoint, ONLY : nksq, npwq, igkq, ikqs
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implicit none
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type (bec_type) :: becq(nksq), alpq(3,nksq)
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! the becp with psi_{k+q}
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! the alphap with psi_{k+q}
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integer :: ik, ikq, ipol, ibnd, ig, ios
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! counter on k points
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! counter on polarizations, bands and
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! used for i/o control
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complex(DP) :: fact
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complex(DP), allocatable :: aux (:,:)
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!
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if (lgamma) return
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IF (rec_code_read >= -20.AND..NOT.okpaw) RETURN
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allocate (aux ( npwx*npol , nbnd))
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if (nksq.gt.1) rewind (iunigk)
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do ik = 1, nksq
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ikq = ikqs(ik)
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if (nksq.gt.1) then
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read (iunigk, err = 100, iostat = ios) npw, igk
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100 call errore ('compute_becalp', 'reading igk', abs (ios) )
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read (iunigk, err = 200, iostat = ios) npwq, igkq
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200 call errore ('compute_becalp', 'reading igkq', abs (ios) )
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endif
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call init_us_2 (npwq, igkq, xk (1, ikq), vkb)
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call davcio (evq, lrwfc, iuwfc, ikq, - 1)
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call calbec ( npwq, vkb, evq, becq(ik) )
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do ipol = 1, 3
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aux=(0.d0,0.d0)
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do ibnd = 1, nbnd
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do ig = 1, npwq
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aux (ig, ibnd) = evq (ig, ibnd) * &
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(xk (ipol, ikq) + g (ipol, igkq(ig) ) )
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enddo
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IF (noncolin) THEN
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do ig = 1, npwq
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aux (ig+npwx, ibnd) = evq (ig+npwx, ibnd) * &
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(xk (ipol, ikq) + g (ipol, igkq(ig) ) )
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enddo
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ENDIF
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enddo
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call calbec ( npwq, vkb, aux, alpq(ipol,ik) )
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enddo
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enddo
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fact = CMPLX(0.d0, tpiba,kind=DP)
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DO ik=1,nksq
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DO ipol=1,3
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IF (noncolin) THEN
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CALL zscal (nkb*nbnd*npol, fact, alpq(ipol,ik)%nc, 1)
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ELSE
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CALL zscal (nkb*nbnd, fact, alpq(ipol,ik)%k, 1)
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ENDIF
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ENDDO
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ENDDO
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deallocate (aux)
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return
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end subroutine compute_becalp
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