mirror of https://gitlab.com/QEF/q-e.git
63 lines
1.6 KiB
Fortran
63 lines
1.6 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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!
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!-----------------------------------------------------------------------
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subroutine trntns (phi, at, bg, iflg)
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!-----------------------------------------------------------------------
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!
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! trasforms a tensor (like the stress)
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! from crystal to cartesian axis (iflg >= 1) or viceversa (iflg <= -1)
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!
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USE kinds
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implicit none
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integer :: iflg, i, j, k, l
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real(kind=DP) :: phi (3, 3), wrk (3, 3), at (3, 3), bg (3, 3)
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!
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if (iflg.gt.0) then
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!
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! forward transformation (crystal to cartesian axis)
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!
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do i = 1, 3
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do j = 1, 3
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wrk (i, j) = phi (i, j)
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enddo
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enddo
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do i = 1, 3
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do j = 1, 3
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phi (i, j) = 0.0
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do k = 1, 3
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do l = 1, 3
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phi (i, j) = phi (i, j) + wrk (k, l) * bg (i, k) * bg (j, l)
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enddo
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enddo
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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 (cartesian to crystal axis)
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!
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do i = 1, 3
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do j = 1, 3
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wrk (i, j) = 0.0
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do k = 1, 3
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do l = 1, 3
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wrk (i, j) = wrk (i, j) + phi (k, l) * at (k, i) * at (l, j)
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enddo
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enddo
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enddo
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enddo
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do i = 1, 3
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do j = 1, 3
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phi (i, j) = wrk (i, j)
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enddo
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enddo
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endif
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!
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return
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end subroutine trntns
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