quantum-espresso/PHonon/PH/rotate_and_add_dyn.f90

73 lines
2.3 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 rotate_and_add_dyn (phi, phi2, nat, isym, s, invs, irt, &
rtau, sxq)
!-----------------------------------------------------------------------
! Rotates a dynamical matrix (phi) in crystal coordinates according
! to the specified symmetry operation and add the rotated matrix
! to phi2. phi is left unmodified.
!
USE kinds, only : DP
USE constants, ONLY : tpi
implicit none
! input variables
integer :: nat, isym, s (3, 3, 48), invs (48), irt (48, nat)
! number of atoms in the unit cell
! index of the symm.op.
! the symmetry operations
! index of the inverse operations
! index of the rotated atom
complex(DP) :: phi (3, 3, nat, nat), phi2 (3, 3, nat, nat)
! the input dyn.mat. in crystal coordinates
! the rotated dyn.mat. in crystal coordinates
real(DP) :: rtau (3, 48, nat), sxq (3)
! for eaxh atom and rotation gives the R vector
!involved
! the rotated q involved in this sym.op.
! local variables
integer :: na, nb, sna, snb, ism1, i, j, k, l
! counters on atoms
! indices of rotated atoms
! index of the inverse symm.op.
! generic counters
real(DP) :: arg
! argument of the phase
complex(DP) :: phase, work
ism1 = invs (isym)
do na = 1, nat
do nb = 1, nat
sna = irt (isym, na)
snb = irt (isym, nb)
arg = (sxq (1) * (rtau (1, isym, na) - rtau (1, isym, nb) ) &
+ sxq (2) * (rtau (2, isym, na) - rtau (2, isym, nb) ) + sxq (3) &
* (rtau (3, isym, na) - rtau (3, isym, nb) ) ) * tpi
phase = CMPLX(cos (arg), - sin (arg) ,kind=DP)
do i = 1, 3
do j = 1, 3
work = CMPLX(0.d0, 0.d0,kind=DP)
do k = 1, 3
do l = 1, 3
work = work + s (i, k, ism1) * s (j, l, ism1) * phi (k, l, na, nb) &
* phase
enddo
enddo
phi2 (i, j, sna, snb) = phi2 (i, j, sna, snb) + work
enddo
enddo
enddo
enddo
!
return
end subroutine rotate_and_add_dyn