mirror of https://gitlab.com/QEF/q-e.git
68 lines
1.5 KiB
Fortran
68 lines
1.5 KiB
Fortran
!
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! Copyright (C) 2001 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 trnvecc (u, at, bg, iflg)
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!-----------------------------------------------------------------------
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!
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! transforms a COMPLEX vector in real space (like a displacement)
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! from crystal to cartesian axis (iflag.gt.0) and viceversa (iflag.le.0
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!
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USE kinds, only : DP
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implicit none
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integer :: iflg
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! input: gives the versus of the transformatio
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real(DP) :: at (3, 3), bg (3, 3)
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! input: the direct lattice vectors
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! input: the reciprocal lattice vectors
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complex(DP) :: u (3)
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! inp/out: the vector to transform
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integer :: i, k
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! \
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! counter on polarizations
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!/
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complex(DP) :: wrk (3)
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! auxiliary variable
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if (iflg.gt.0) then
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!
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! forward transformation :
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!
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do i = 1, 3
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wrk (i) = u (i)
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enddo
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do i = 1, 3
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u (i) = 0.d0
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do k = 1, 3
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u (i) = u (i) + wrk (k) * at (i, k)
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enddo
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enddo
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else
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!
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! backward transformation :
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!
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do i = 1, 3
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wrk (i) = 0.d0
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do k = 1, 3
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wrk (i) = wrk (i) + u (k) * bg (k, i)
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enddo
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enddo
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do i = 1, 3
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u (i) = wrk (i)
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enddo
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endif
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return
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end subroutine trnvecc
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