mirror of https://gitlab.com/QEF/q-e.git
124 lines
3.6 KiB
Fortran
124 lines
3.6 KiB
Fortran
!
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! Copyright (C) 2001-2018 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_weight (wgg)
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!-----------------------------------------------------------------------
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!! This routine implements Eq.(B19) of PRB 64, 235118 (2001). It computes the
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!! weight to give to the v,v' terms in the orthogonality term.
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!! The weights are computed for each k point.
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!
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USE kinds, ONLY : DP
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USE klist, ONLY : wk, lgauss, degauss, ngauss, ltetra, degauss_cond
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USE ener, ONLY : ef, ef_cond
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USE wvfct, ONLY : nbnd, wg, et, nbnd_cond
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USE paw_variables, ONLY : okpaw
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USE qpoint, ONLY : nksq, ikks, ikqs
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USE control_lr, ONLY : rec_code_read
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USE dfpt_tetra_mod, ONLY : dfpt_tetra_ttheta
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USE ldaU, ONLY : lda_plus_u
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USE two_chem, ONLY : twochem
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!
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implicit none
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!
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real(DP) :: wgg(nbnd,nbnd,nksq)
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!! output: the weights
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!
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! ... local variables
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!
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integer :: ik, ikk, ikq, ibnd, jbnd
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! counters
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real(DP) :: wg1, wg2, theta
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! auxiliary variables
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real(DP), external :: wgauss
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real(DP), parameter :: eps = 1.0d-12
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!
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! DFPT+U: in the recover case the weights have to be computed in
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! the routine dyn_hub_scf routine.
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!
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IF (lda_plus_u) GO TO 100
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!
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IF ((rec_code_read >= -20) .AND. (.NOT.okpaw)) RETURN
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!
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100 CONTINUE
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!
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IF(ltetra) THEN
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!
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DO ik = 1, nksq
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DO ibnd = 1,nbnd
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DO jbnd = 1, nbnd
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wgg(ibnd, jbnd, ik) = dfpt_tetra_ttheta(jbnd, ibnd, ikks(ik))
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END DO
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END DO
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END DO
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!
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return
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!
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END IF
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!
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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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!
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! each band v ...
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!
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do ibnd = 1, nbnd
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if (wk (ikk) .eq.0.d0) then
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wg1 = 0.d0
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else
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wg1 = wg (ibnd, ikk) / wk (ikk)
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!two chemical potentials case
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if (twochem) then
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if (ibnd.gt.(nbnd-nbnd_cond)) then
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wg1 = wgauss ( (ef_cond - et (ibnd, ikk) ) / degauss_cond, ngauss)
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else
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wg1 = wgauss ( (ef - et (ibnd, ikk) ) / degauss, ngauss)
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end if
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end if
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endif
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!
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! and each band v' ...
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!
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do jbnd = 1, nbnd
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if (lgauss) then
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theta = wgauss ( (et (jbnd,ikq) - et (ibnd,ikk) ) / degauss, 0)
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wg2 = wgauss ( (ef - et (jbnd, ikq) ) / degauss, ngauss)
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! two chemical potentials case
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if (twochem) then
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if (jbnd.gt.(nbnd-nbnd_cond)) then
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wg2 = wgauss ( (ef_cond - et (jbnd, ikq) ) / degauss_cond, ngauss)
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end if
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end if
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else
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IF (et (jbnd,ikq) > et (ibnd,ikk)) THEN
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theta = 1.0d0
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ELSE
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theta = 0.d0
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ENDIF
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IF (ABS(et (jbnd,ikq) - et (ibnd,ikk)) < 1.d-8) theta=0.5d0
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if (wk (ikk) .le.eps) then
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wg2 = 0.d0
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else
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wg2 = wg (jbnd, ikk) / wk (ikk)
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endif
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endif
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wgg (ibnd, jbnd, ik) = wg1 * (1.d0 - theta) + wg2 * theta
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enddo
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enddo
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! do ibnd=1,nbnd
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! do jbnd=1,nbnd
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! WRITE( stdout,'(3i5,f20.10)') ibnd, jbnd, ik,wgg(ibnd,jbnd,ik)
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! enddo
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! enddo
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enddo
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! call stop_ph(.true.)
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return
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end subroutine compute_weight
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