quantum-espresso/PHonon/PH/q2qstar_ph.f90

162 lines
4.8 KiB
Fortran

!
! Copyright (C) 2001 PWSCF group
! This file is distributed under the terms of the
! GNU General Public License. See the file `License'
! in the root directory of the present distribution,
! or http://www.gnu.org/copyleft/gpl.txt .
!
!-----------------------------------------------------------------------
subroutine q2qstar_ph (dyn, at, bg, nat, nsym, s, invs, irt, rtau, &
nq, sxq, isq, imq, iudyn)
!-----------------------------------------------------------------------
! Generates the dynamical matrices for the star of q and writes them on
! disk for later use.
! If there is a symmetry operation such that q -> -q +G then imposes on
! dynamical matrix those conditions related to time reversal symmetry.
!
USE kinds, only : DP
USE io_dyn_mat, only : write_dyn_mat
USE control_ph, only : xmldyn
implicit none
! input variables
integer :: nat, nsym, s (3, 3, 48), invs (48), irt (48, nat), &
nq, isq (48), imq, iudyn
! number of atoms in the unit cell
! number of symmetry operations
! the symmetry operations
! index of the inverse operations
! index of the rotated atom
! degeneracy of the star of q
! symmetry op. giving the rotated q
! index of -q in the star (0 if non present)
! unit number
complex(DP) :: dyn (3 * nat, 3 * nat)
! the input dynamical matrix. if imq.ne.0 the
! output matrix is symmetrized w.r.t. time-reversal
real(DP) :: at (3, 3), bg (3, 3), rtau (3, 48, nat), sxq (3, 48)
! direct lattice vectors
! reciprocal lattice vectors
! for each atom and rotation gives the R vector involved
! list of q in the star
!
! local variables
integer :: na, nb, iq, nsq, isym, icar, jcar, i, j, counter
! counters
! nsq: number of sym.op. giving each q in the list
complex(DP) :: phi (3, 3, nat, nat), phi2 (3, 3, nat, nat)
! work space
counter=0
!
! Sets number of symmetry operations giving each q in the list
!
nsq = nsym / nq
if (nsq * nq /= nsym) call errore ('q2star_ph', 'wrong degeneracy', 1)
!
! Writes dyn.mat. dyn(3*nat,3*nat) on the 4-index array phi(3,3,nat,nat)
!
CALL scompact_dyn(nat, dyn, phi)
!
! Go to crystal coordinates
!
do na = 1, nat
do nb = 1, nat
call trntnsc (phi (1, 1, na, nb), at, bg, - 1)
enddo
enddo
!
! If -q is in the list impose first of all the conditions coming from
! time reversal symmetry
!
if (imq /= 0) then
phi2 (:,:,:,:) = (0.d0, 0.d0)
isym = 1
do while (isq (isym) /= imq)
isym = isym + 1
enddo
call rotate_and_add_dyn (phi, phi2, nat, isym, s, invs, irt, &
rtau, sxq (1, imq) )
do na = 1, nat
do nb = 1, nat
do i = 1, 3
do j = 1, 3
phi (i, j, na, nb) = 0.5d0 * (phi (i, j, na, nb) + &
CONJG(phi2(i, j, na, nb) ) )
enddo
enddo
enddo
enddo
phi2 (:,:,:,:) = phi (:,:,:,:)
!
! Back to cartesian coordinates
!
do na = 1, nat
do nb = 1, nat
call trntnsc (phi2 (1, 1, na, nb), at, bg, + 1)
enddo
enddo
!
! Saves 4-index array phi2(3,3,nat,nat) on the dyn.mat. dyn(3*nat,3*nat)
!
CALL compact_dyn(nat, dyn, phi2)
endif
!
! For each q of the star rotates phi with the appropriate sym.op. -> phi
!
do iq = 1, nq
phi2 (:,:,:,:) = (0.d0, 0.d0)
do isym = 1, nsym
if (isq (isym) == iq) then
call rotate_and_add_dyn (phi, phi2, nat, isym, s, invs, irt, &
rtau, sxq (1, iq) )
endif
enddo
phi2 (:,:,:,:) = phi2 (:,:,:,:) / DBLE (nsq)
!
! Back to cartesian coordinates
!
do na = 1, nat
do nb = 1, nat
call trntnsc (phi2 (1, 1, na, nb), at, bg, + 1)
enddo
enddo
!
! Writes the dynamical matrix in cartesian coordinates on file
!
counter=counter+1
IF (xmldyn) THEN
call write_dyn_mat(nat, counter, sxq(1,iq), phi2)
ELSE
call write_dyn_on_file (sxq (1, iq), phi2, nat, iudyn)
ENDIF
if (imq == 0) then
!
! if -q is not in the star recovers its matrix by time reversal
!
do na = 1, nat
do nb = 1, nat
do i = 1, 3
do j = 1, 3
phi2 (i, j, na, nb) = CONJG(phi2 (i, j, na, nb) )
enddo
enddo
enddo
enddo
!
! and writes it (changing temporarily sign to q)
!
sxq (:, iq) = - sxq (:, iq)
counter=counter+1
IF (xmldyn) THEN
call write_dyn_mat(nat, counter, sxq(1,iq), phi2)
ELSE
call write_dyn_on_file (sxq (1, iq), phi2, nat, iudyn)
ENDIF
sxq (:, iq) = - sxq (:, iq)
endif
enddo
!
return
end subroutine q2qstar_ph