mirror of https://gitlab.com/QEF/q-e.git
180 lines
6.2 KiB
Fortran
180 lines
6.2 KiB
Fortran
!
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! Copyright (C) 2001-2012 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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subroutine symdynph_gq_new (xq, phi, s, invs, rtau, irt, nsymq, &
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nat, irotmq, minus_q)
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!-----------------------------------------------------------------------
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!
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! This routine receives as input an unsymmetrized dynamical
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! matrix expressed on the crystal axes and imposes the symmetry
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! of the small group of q. Furthermore it imposes also the symmetry
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! q -> -q+G if present.
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! February 2020: Update (A. Urru) to include the symmetry operations
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! that require the time reversal operator (meaning that TS is a
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! symmetry of the crystal). For more information please see:
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! Phys. Rev. B 100, 045115 (2019)
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!
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!
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USE kinds, only : DP
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USE constants, ONLY: tpi
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USE symm_base, ONLY : t_rev
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implicit none
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!
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! The dummy variables
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!
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integer :: nat, s (3, 3, 48), irt (48, nat), invs (48), &
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nsymq, irotmq
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! input: the number of atoms
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! input: the symmetry matrices
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! input: the rotated of each vector
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! input: the small group of q
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! input: the inverse of each matrix
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! input: the order of the small gro
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! input: the rotation sending q ->
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real(DP) :: xq (3), rtau (3, 48, nat)
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! input: the q point
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! input: the R associated at each t
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logical :: minus_q
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! input: true if a symmetry q->-q+G
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complex(DP) :: phi (3, 3, nat, nat)
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! inp/out: the matrix to symmetrize
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!
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! local variables
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!
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integer :: isymq, sna, snb, irot, na, nb, ipol, jpol, lpol, kpol, &
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iflb (nat, nat)
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! counters, indices, work space
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real(DP) :: arg
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! the argument of the phase
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complex(DP) :: phip (3, 3, nat, nat), work (3, 3), fase, faseq (48)
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! work space, phase factors
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!
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! We start by imposing hermiticity
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!
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do na = 1, nat
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do nb = 1, nat
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do ipol = 1, 3
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do jpol = 1, 3
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phi (ipol, jpol, na, nb) = 0.5d0 * (phi (ipol, jpol, na, nb) &
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+ CONJG(phi (jpol, ipol, nb, na) ) )
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phi (jpol, ipol, nb, na) = CONJG(phi (ipol, jpol, na, nb) )
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enddo
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enddo
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enddo
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enddo
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!
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! If no other symmetry is present we quit here
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!
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if ( (nsymq == 1) .and. (.not.minus_q) ) return
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!
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! Then we impose the symmetry q -> -q+G if present
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!
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if (minus_q) then
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do na = 1, nat
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do nb = 1, nat
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do ipol = 1, 3
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do jpol = 1, 3
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work(:,:) = (0.d0, 0.d0)
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sna = irt (irotmq, na)
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snb = irt (irotmq, nb)
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arg = 0.d0
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do kpol = 1, 3
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arg = arg + (xq (kpol) * (rtau (kpol, irotmq, na) - &
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rtau (kpol, irotmq, nb) ) )
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enddo
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arg = arg * tpi
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fase = CMPLX(cos (arg), sin (arg) ,kind=DP)
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do kpol = 1, 3
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do lpol = 1, 3
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work (ipol, jpol) = work (ipol, jpol) + &
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s (ipol, kpol, irotmq) * s (jpol, lpol, irotmq) &
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* phi (kpol, lpol, sna, snb) * fase
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enddo
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enddo
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phip (ipol, jpol, na, nb) = (phi (ipol, jpol, na, nb) + &
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CONJG( work (ipol, jpol) ) ) * 0.5d0
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enddo
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enddo
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enddo
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enddo
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phi = phip
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endif
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!
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! Here we symmetrize with respect to the small group of q
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!
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if (nsymq == 1) return
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iflb (:, :) = 0
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do na = 1, nat
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do nb = 1, nat
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if (iflb (na, nb) == 0) then
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work(:,:) = (0.d0, 0.d0)
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do isymq = 1, nsymq
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irot = isymq
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sna = irt (irot, na)
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snb = irt (irot, nb)
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arg = 0.d0
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do ipol = 1, 3
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arg = arg + (xq (ipol) * (rtau (ipol, irot, na) - &
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rtau (ipol, irot, nb) ) )
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enddo
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arg = arg * tpi
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faseq (isymq) = CMPLX(cos (arg), sin (arg) ,kind=DP)
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do ipol = 1, 3
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do jpol = 1, 3
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do kpol = 1, 3
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do lpol = 1, 3
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IF (t_rev(isymq)==1) THEN
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work (ipol, jpol) = work (ipol, jpol) + &
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s (ipol, kpol, irot) * s (jpol, lpol, irot) &
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* CONJG(phi (kpol, lpol, sna, snb) * faseq (isymq))
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ELSE
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work (ipol, jpol) = work (ipol, jpol) + &
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s (ipol, kpol, irot) * s (jpol, lpol, irot) &
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* phi (kpol, lpol, sna, snb) * faseq (isymq)
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ENDIF
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enddo
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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 isymq = 1, nsymq
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irot = isymq
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sna = irt (irot, na)
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snb = irt (irot, nb)
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do ipol = 1, 3
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do jpol = 1, 3
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phi (ipol, jpol, sna, snb) = (0.d0, 0.d0)
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do kpol = 1, 3
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do lpol = 1, 3
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IF (t_rev(isymq)==1) THEN
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phi(ipol,jpol,sna,snb)=phi(ipol,jpol,sna,snb) &
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+ s(ipol,kpol,invs(irot))*s(jpol,lpol,invs(irot))&
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* CONJG(work (kpol, lpol)*faseq (isymq))
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ELSE
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phi(ipol,jpol,sna,snb)=phi(ipol,jpol,sna,snb) &
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+ s(ipol,kpol,invs(irot))*s(jpol,lpol,invs(irot))&
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* work (kpol, lpol) * CONJG(faseq (isymq) )
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ENDIF
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enddo
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enddo
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enddo
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enddo
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iflb (sna, snb) = 1
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enddo
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endif
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enddo
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enddo
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phi (:, :, :, :) = phi (:, :, :, :) / DBLE(nsymq)
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return
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end subroutine symdynph_gq_new
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