mirror of https://gitlab.com/QEF/q-e.git
82 lines
2.7 KiB
Fortran
82 lines
2.7 KiB
Fortran
!
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! Copyright (C) 2002 FPMD 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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MODULE small_box
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!------------------------------------------------------------------------------!
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! This module contains the basis vector of the small sub-cell (small box)
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! used for charge augmentation process
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USE kinds, ONLY : DP
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!
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IMPLICIT NONE
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SAVE
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! a1, a2 and a3 are the simulation cell base vector as calculated from celldm
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REAL(DP) :: a1b(3) = (/ 0.0d0, 0.0d0, 0.0d0 /)
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REAL(DP) :: a2b(3) = (/ 0.0d0, 0.0d0, 0.0d0 /)
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REAL(DP) :: a3b(3) = (/ 0.0d0, 0.0d0, 0.0d0 /)
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REAL(DP) :: b1b(3) = (/ 0.0d0, 0.0d0, 0.0d0 /)
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REAL(DP) :: b2b(3) = (/ 0.0d0, 0.0d0, 0.0d0 /)
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REAL(DP) :: b3b(3) = (/ 0.0d0, 0.0d0, 0.0d0 /)
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REAL(DP) :: ainvb(3,3) = 0.0d0
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REAl(DP) :: omegab = 0.0d0 ! volume of the small boxes
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REAL(DP) :: tpibab = 0.0d0
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REAL(DP) :: alatb = 0.0d0
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!------------------------------------------------------------------------------!
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CONTAINS
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!------------------------------------------------------------------------------!
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!
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SUBROUTINE small_box_set( alat, omega, a1, a2, a3, rat1, rat2, rat3 )
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USE constants, ONLY: pi
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USE io_global, ONLY: stdout
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IMPLICIT NONE
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REAL(DP), INTENT(IN) :: alat, omega, a1(3), a2(3), a3(3), rat1, rat2, rat3
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INTEGER :: i
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alatb = alat * rat1
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IF( alatb <= 0.0d0 ) CALL errore(' small_box_set ', ' alatb <= 0 ', 1 )
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tpibab = 2.d0 * pi / alatb
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a1b = a1 * rat1
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a2b = a2 * rat2
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a3b = a3 * rat3
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omegab = omega * rat1 * rat2 * rat3
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!
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CALL recips( a1b, a2b, a3b, b1b, b2b, b3b )
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b1b = b1b * alatb
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b2b = b2b * alatb
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b3b = b3b * alatb
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WRITE( stdout,*)
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WRITE( stdout,220)
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220 format( 3X, 'unit vectors of box grid cell',/, &
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& 3X, 'in real space:',25x,'in reciprocal space:')
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WRITE( stdout,'(3X,3f10.4,10x,3f10.4)') a1b, b1b
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WRITE( stdout,'(3X,3f10.4,10x,3f10.4)') a2b, b2b
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WRITE( stdout,'(3X,3f10.4,10x,3f10.4)') a3b, b3b
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ainvb(1,:) = b1b(:) / alatb
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ainvb(2,:) = b2b(:) / alatb
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ainvb(3,:) = b3b(:) / alatb
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RETURN
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END SUBROUTINE small_box_set
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!
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!------------------------------------------------------------------------------!
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END MODULE small_box
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!------------------------------------------------------------------------------!
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