2003-01-20 05:58:50 +08:00
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!
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2009-08-03 17:19:02 +08:00
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! Copyright (C) 2001-2008 Quantum ESPRESSO group
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2003-01-20 05:58:50 +08:00
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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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2003-02-08 00:04:36 +08:00
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subroutine compute_weight (wgg)
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2003-03-27 23:47:30 +08:00
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!-----------------------------------------------------------------------
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!
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2009-02-12 16:56:50 +08:00
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! This routine implements Eq.B19 of Ref.[1]. It computes the
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! weight to give to the v,v' terms in the orthogonality term.
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! [1] PRB 64, 235118 (2001).
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2003-03-27 23:47:30 +08:00
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!
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2003-01-20 05:58:50 +08:00
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2008-09-24 19:50:31 +08:00
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USE kinds, ONLY : DP
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USE klist, ONLY : wk, lgauss, degauss, ngauss
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USE ener, ONLY : ef
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USE wvfct, ONLY : nbnd, wg, et
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2009-11-17 01:04:25 +08:00
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USE paw_variables, ONLY : okpaw
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2009-02-04 18:25:03 +08:00
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USE qpoint, ONLY : nksq, ikks, ikqs
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2009-11-17 01:04:25 +08:00
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USE control_ph, ONLY : rec_code_read
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2003-03-27 23:47:30 +08:00
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implicit none
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2003-01-20 05:58:50 +08:00
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2005-08-28 22:09:42 +08:00
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real(DP) :: wgg (nbnd, nbnd, nksq)
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2003-03-27 23:47:30 +08:00
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! output: the weights
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2003-01-20 05:58:50 +08:00
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2003-03-27 23:47:30 +08:00
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integer :: ik, ikk, ikq, ibnd, jbnd
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! counters
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2005-08-28 22:09:42 +08:00
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real(DP) :: wg1, wg2, theta
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2003-03-27 23:47:30 +08:00
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! auxiliary variables
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2005-08-28 22:09:42 +08:00
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real(DP), external :: wgauss
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real(DP), parameter :: eps = 1.0d-12
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2003-03-27 23:47:30 +08:00
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!
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! the weights are computed for each k point ...
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!
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2009-11-17 01:04:25 +08:00
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if (rec_code_read >= -20.AND..NOT.okpaw) return
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2003-03-27 23:47:30 +08:00
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do ik = 1, nksq
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2009-02-04 18:25:03 +08:00
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ikk = ikks(ik)
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ikq = ikqs(ik)
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2003-03-27 23:47:30 +08:00
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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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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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2006-12-19 02:28:42 +08:00
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if (lgauss) then
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2003-03-27 23:47:30 +08:00
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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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else
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2006-11-22 18:54:28 +08:00
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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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2003-03-27 23:47:30 +08:00
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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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2003-11-06 03:01:20 +08:00
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! WRITE( stdout,'(3i5,f20.10)') ibnd, jbnd, ik,wgg(ibnd,jbnd,ik)
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2003-03-27 23:47:30 +08:00
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! enddo
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! enddo
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2003-01-20 05:58:50 +08:00
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2003-03-27 23:47:30 +08:00
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enddo
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! call stop_ph(.true.)
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return
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2003-01-20 05:58:50 +08:00
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end subroutine compute_weight
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