mirror of https://gitlab.com/QEF/q-e.git
93 lines
3.0 KiB
Fortran
93 lines
3.0 KiB
Fortran
! Copyright (C) 2002-2004 PWSCF 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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#include "f_defs.h"
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!
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!-----------------------------------------------------------------------
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SUBROUTINE dndtau_of_k(dns,ldim,offset,proj,wfcatom,spsi,alpha,ipol,ik)
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!-----------------------------------------------------------------------
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!
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! This routine computes the derivative of the ns with respect to the ionic
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! displacement u(alpha,ipol) used to obtain the Hubbard contribution to the
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! atomic forces.
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!
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USE kinds, ONLY : DP
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USE ions_base, ONLY : nat, ityp
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USE basis, ONLY : natomwfc
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USE lsda_mod, ONLY : nspin, current_spin
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USE ldaU, ONLY : Hubbard_U, Hubbard_alpha
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USE wvfct, ONLY : nbnd, npwx, npw, wg
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IMPLICIT NONE
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INTEGER :: alpha, ipol, &
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ik, ibnd, is, na, nt, m1, m2
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INTEGER :: ldim
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REAL (kind=DP) :: &
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dns(ldim,ldim,nspin,nat)
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INTEGER :: offset(nat)
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! offset(nat): offset of d electrons of atom d in the natomwfc ordering
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COMPLEX (kind=DP) :: &
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proj(natomwfc,nbnd), wfcatom(npwx,natomwfc), spsi(npwx,nbnd)
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! COMPLEX (kind=DP) :: ZDOTC, c_one, c_zero
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COMPLEX (kind=DP), ALLOCATABLE :: &
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dproj(:,:)
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! dproj(natomwfc,nbnd)
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CALL start_clock('dndtau_of_k')
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ALLOCATE ( dproj(natomwfc,nbnd) )
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dns(:,:,:,:) = 0.d0
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!
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dproj(:,:) = (0.d0,0.d0)
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CALL dprojdtau(dproj,wfcatom,spsi,alpha,ipol,offset(alpha))
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!
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! compute the derivative of occupation numbers (the quantities dn(m1,m2))
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! of the atomic orbitals. They are real quantities as well as n(m1,m2)
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!
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DO na = 1,nat
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nt = ityp(na)
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IF (Hubbard_U(nt).NE.0.d0.OR.Hubbard_alpha(nt).NE.0.d0) THEN
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DO m1 = 1,ldim
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DO m2 = m1,ldim
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DO ibnd = 1,nbnd
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dns(m1,m2,current_spin,na) = dns(m1,m2,current_spin,na) + &
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wg(ibnd,ik) * &
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DREAL( proj(offset(na)+m1,ibnd) * &
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CONJG(dproj(offset(na)+m2,ibnd)) + &
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dproj(offset(na)+m1,ibnd) * &
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CONJG(proj(offset(na)+m2,ibnd)) )
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END DO
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END DO
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END DO
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END IF
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END DO
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!
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! In nspin.eq.1 k-point weight wg is normalized to 2 el/band
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! in the whole BZ but we are interested in dns of one spin component
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!
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IF (nspin.EQ.1) dns = 0.5d0 * dns
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!
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! impose hermiticity of dn_{m1,m2}
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!
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DO na = 1,nat
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DO is = 1,nspin
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DO m1 = 1,ldim
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DO m2 = m1+1,ldim
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dns(m2,m1,is,na) = dns(m1,m2,is,na)
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END DO
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END DO
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END DO
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END DO
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DEALLOCATE ( dproj )
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CALL stop_clock('dndtau_of_k')
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RETURN
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END SUBROUTINE dndtau_of_k
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