mirror of https://gitlab.com/QEF/q-e.git
96 lines
2.9 KiB
Fortran
96 lines
2.9 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 random_matrix (irt, irgq, nsymq, minus_q, irotmq, nat, &
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wdyn, lgamma)
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!----------------------------------------------------------------------
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!
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! Create a random hermitian matrix with non zero elements similar to
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! the dynamical matrix of the system
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!
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!
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#include "machine.h"
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use parameters, only : DP
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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, irt (48, nat), irgq (48), nsymq, irotmq
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! input: number of atoms
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! input: index of the rotated atom
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! input: the small group of q
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! input: the order of the small group
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! input: the rotation sending q -> -q
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complex(kind=DP) :: wdyn (3, 3, nat, nat)
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! output: random matrix
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logical :: lgamma, minus_q
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! input: if true q=0
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! input: if true there is a symmetry
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!
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! The local variables
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!
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integer :: na, nb, ipol, jpol, isymq, irot, ira, iramq
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! counter on atoms
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! counter on atoms
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! counter on polarizations
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! counter on polarizations
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! counter on symmetries
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! counter on rotations
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! the rotated atom
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! the rotated atom with the q->-q+G s
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real(kind=DP) :: rndm, arg
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! a function giving a random number
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! dummy variable
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external rndm
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call setv (2 * 3 * nat * 3 * nat, 0d0, wdyn, 1)
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do na = 1, nat
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do ipol = 1, 3
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wdyn (ipol, ipol, na, na) = DCMPLX (2 * rndm () - 1, 0.d0)
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do jpol = ipol + 1, 3
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if (lgamma) then
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wdyn (ipol, jpol, na, na) = DCMPLX (2 * rndm () - 1, 0.d0)
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else
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wdyn (ipol, jpol, na, na) = DCMPLX (2 * rndm () - 1, 2 * rndm ( &
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) - 1)
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endif
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wdyn (jpol, ipol, na, na) = conjg (wdyn (ipol, jpol, na, na) )
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enddo
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do nb = na + 1, nat
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do isymq = 1, nsymq
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irot = irgq (isymq)
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ira = irt (irot, na)
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if (minus_q) then
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iramq = irt (irotmq, na)
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else
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iramq = 0
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endif
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if ( (nb.eq.ira) .or. (nb.eq.iramq) ) then
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do jpol = 1, 3
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if (lgamma) then
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wdyn (ipol, jpol, na, nb) = DCMPLX (2 * rndm () - 1, 0.d0)
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else
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wdyn (ipol, jpol, na, nb) = DCMPLX (2 * rndm () - 1, 2 * &
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rndm () - 1)
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endif
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wdyn (jpol, ipol, nb, na) = conjg (wdyn (ipol, jpol, na, nb) )
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enddo
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goto 10
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endif
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enddo
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10 continue
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enddo
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enddo
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enddo
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return
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end subroutine random_matrix
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