mirror of https://gitlab.com/QEF/q-e.git
165 lines
4.8 KiB
Fortran
165 lines
4.8 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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subroutine q2qstar_ph (dyn, at, bg, nat, nsym, s, invs, irt, rtau, &
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nq, sxq, isq, imq, iudyn)
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!-----------------------------------------------------------------------
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! Generates the dynamical matrices for the star of q and writes them on
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! disk for later use.
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! If there is a symmetry operation such that q -> -q +G then imposes on
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! dynamical matrix those conditions related to time reversal symmetry.
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!
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USE kinds, only : DP
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implicit none
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! input variables
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integer :: nat, nsym, s (3, 3, 48), invs (48), irt (48, nat), &
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nq, isq (48), imq, iudyn
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! number of atoms in the unit cell
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! number of symmetry operations
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! the symmetry operations
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! index of the inverse operations
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! index of the rotated atom
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! degeneracy of the star of q
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! symmetry op. giving the rotated q
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! index of -q in the star (0 if non present)
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! unit number
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complex(DP) :: dyn (3 * nat, 3 * nat)
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! the input dynamical matrix. if imq.ne.0 the
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! output matrix is symmetrized w.r.t. time-reversal
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real(DP) :: at (3, 3), bg (3, 3), rtau (3, 48, nat), sxq (3, 48)
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! direct lattice vectors
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! reciprocal lattice vectors
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! for each atom and rotation gives the R vector involved
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! list of q in the star
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!
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! local variables
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integer :: na, nb, iq, nsq, isym, icar, jcar, i, j
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! counters
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! nsq: number of sym.op. giving each q in the list
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complex(DP) :: phi (3, 3, nat, nat), phi2 (3, 3, nat, nat)
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! work space
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!
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! Sets number of symmetry operations giving each q in the list
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!
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nsq = nsym / nq
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if (nsq * nq /= nsym) call errore ('q2star_ph', 'wrong degeneracy', 1)
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!
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! Writes dyn.mat. dyn(3*nat,3*nat) on the 4-index array phi(3,3,nat,nta)
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!
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do i = 1, 3 * nat
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na = (i - 1) / 3 + 1
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icar = i - 3 * (na - 1)
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do j = 1, 3 * nat
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nb = (j - 1) / 3 + 1
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jcar = j - 3 * (nb - 1)
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phi (icar, jcar, na, nb) = dyn (i, j)
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enddo
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enddo
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!
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! Go to crystal coordinates
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!
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do na = 1, nat
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do nb = 1, nat
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call trntnsc (phi (1, 1, na, nb), at, bg, - 1)
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enddo
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enddo
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!
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! If -q is in the list impose first of all the conditions coming from
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! time reversal symmetry
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!
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if (imq /= 0) then
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phi2 (:,:,:,:) = (0.d0, 0.d0)
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isym = 1
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do while (isq (isym) /= imq)
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isym = isym + 1
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enddo
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call rotate_and_add_dyn (phi, phi2, nat, isym, s, invs, irt, &
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rtau, sxq (1, imq) )
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do na = 1, nat
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do nb = 1, nat
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do i = 1, 3
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do j = 1, 3
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phi (i, j, na, nb) = 0.5d0 * (phi (i, j, na, nb) + &
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CONJG(phi2(i, j, 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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phi2 (:,:,:,:) = phi (:,:,:,:)
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!
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! Back to cartesian coordinates
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!
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do na = 1, nat
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do nb = 1, nat
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call trntnsc (phi2 (1, 1, na, nb), at, bg, + 1)
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enddo
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enddo
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!
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! Saves 4-index array phi(3,3,nat,nta) on the dyn.mat. dyn(3*nat,3*nat)
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!
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do i = 1, 3 * nat
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na = (i - 1) / 3 + 1
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icar = i - 3 * (na - 1)
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do j = 1, 3 * nat
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nb = (j - 1) / 3 + 1
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jcar = j - 3 * (nb - 1)
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dyn (i, j) = phi2 (icar, jcar, na, nb)
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enddo
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enddo
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endif
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!
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! For each q of the star rotates phi with the appropriate sym.op. -> phi
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!
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do iq = 1, nq
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phi2 (:,:,:,:) = (0.d0, 0.d0)
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do isym = 1, nsym
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if (isq (isym) == iq) then
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call rotate_and_add_dyn (phi, phi2, nat, isym, s, invs, irt, &
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rtau, sxq (1, iq) )
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endif
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enddo
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phi2 (:,:,:,:) = phi2 (:,:,:,:) / DBLE (nsq)
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!
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! Back to cartesian coordinates
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!
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do na = 1, nat
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do nb = 1, nat
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call trntnsc (phi2 (1, 1, na, nb), at, bg, + 1)
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enddo
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enddo
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!
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! Writes the dynamical matrix in cartesian coordinates on file
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!
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call write_dyn_on_file (sxq (1, iq), phi2, nat, iudyn)
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if (imq == 0) then
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!
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! if -q is not in the star recovers its matrix by time reversal
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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 i = 1, 3
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do j = 1, 3
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phi2 (i, j, na, nb) = CONJG(phi2 (i, j, 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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! and writes it (changing temporarily sign to q)
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!
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sxq (:, iq) = - sxq (:, iq)
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call write_dyn_on_file (sxq (1, iq), phi2, nat, iudyn)
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sxq (:, iq) = - sxq (:, iq)
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endif
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enddo
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!
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return
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end subroutine q2qstar_ph
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