mirror of https://gitlab.com/QEF/q-e.git
114 lines
2.9 KiB
Fortran
Executable File
114 lines
2.9 KiB
Fortran
Executable File
!
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! Copyright (C) 2021 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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FUNCTION lr_dot_magnons(x,y)
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!---------------------------------------------------------------------
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!
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! Extension of lr_dot.f90 to magnons
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!
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USE kinds, ONLY : dp
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USE io_global, ONLY : stdout
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USE klist, ONLY : nks, xk, wk, ngk
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USE lsda_mod, ONLY : nspin
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USE wvfct, ONLY : npwx,nbnd,wg
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USE gvecw, ONLY : gcutw
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USE control_flags, ONLY : gamma_only
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USE gvect, ONLY : gstart, ngm, g
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USE mp, ONLY : mp_sum
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USE mp_global, ONLY : inter_pool_comm, intra_bgrp_comm
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USE noncollin_module, ONLY : noncolin, npol
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USE control_lr, ONLY : nbnd_occ, nbnd_occx
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USE qpoint, ONLY : nksq
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!
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IMPLICIT NONE
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!
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COMPLEX(kind=dp) :: x(npwx*npol,nbnd_occx,nksq,2), &
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y(npwx*npol,nbnd_occx,nksq,2)
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COMPLEX(kind=dp) :: lr_dot_magnons
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REAL(kind=dp) :: degspin
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INTEGER :: ibnd, ik
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!
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CALL start_clock ('lr_dot_magnons')
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!
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lr_dot_magnons = (0.0d0,0.0d0)
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!
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IF (nspin==2) THEN
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degspin = 1.0d0
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ELSE
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degspin = 2.0d0
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ENDIF
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IF (noncolin) degspin = 1.0d0
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!
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CALL lr_dot_k_magnons()
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!
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! lr_dot_magnons = lr_dot_magnons/degspin
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!
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CALL stop_clock ('lr_dot_magnons')
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!
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RETURN
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!
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CONTAINS
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!
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SUBROUTINE lr_dot_k_magnons
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!
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! MAGNONS
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! Noncollinear case is implemented
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!
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USE qpoint, ONLY : ikks, ikqs
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!
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IMPLICIT NONE
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INTEGER :: ios
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INTEGER :: ik, &
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ikk, & ! index of the point k
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ikq, & ! index of the point k+q
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npwq, &! number of the plane-waves at point k+q
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imk
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!
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DO ik = 1, nksq
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!
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ikk = ikks(ik)
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ikq = ikqs(ik)
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npwq = ngk(ikq)
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!
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IF ( mod(ik,2) == 0) THEN
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imk = ikk - 3 ! position of -k
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ELSE
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imk = ikk + 3 ! position of -k
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ENDIF
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!
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! Resonant part (upper batch)
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!
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DO ibnd = 1, nbnd_occ(ikk)
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!
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lr_dot_magnons = lr_dot_magnons + wk(ikk) * &
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dot_product(x(:,ibnd,ik,1),y(:,ibnd,ik,1))
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!
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ENDDO
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!
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! Anti - Resonant part (lower batch)
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!
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DO ibnd = 1, nbnd_occ(imk)
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!
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lr_dot_magnons = lr_dot_magnons + wk(imk) * &
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dot_product(x(:,ibnd,ik,2),y(:,ibnd,ik,2))
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!
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ENDDO
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!
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ENDDO
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!
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#if defined(__MPI)
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CALL mp_sum(lr_dot_magnons, intra_bgrp_comm)
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CALL mp_sum(lr_dot_magnons, inter_pool_comm)
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#endif
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!
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RETURN
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!
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END SUBROUTINE lr_dot_k_magnons
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!
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END FUNCTION lr_dot_magnons
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