mirror of https://gitlab.com/QEF/q-e.git
98 lines
2.8 KiB
Fortran
98 lines
2.8 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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!----------------------------------------------------------------------
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subroutine struc_fact (nat, tau, ntyp, ityp, ngm, g, bg, nr1, nr2, &
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nr3, strf, eigts1, eigts2, eigts3)
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!----------------------------------------------------------------------
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!
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! calculate the structure factors for each type of atoms in the unit
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! cell
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!
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USE kinds
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USE constants, ONLY : tpi
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implicit none
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!
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! Here the dummy variables
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!
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integer :: nat, ntyp, ityp (nat), ngm, nr1, nr2, nr3
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! input: the number of atom in the unit cel
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! input: the number of atom types
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! input: for each atom gives the type
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! input: the number of G vectors
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! input: fft dimension along x
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! input: fft dimension along y
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! input: fft dimension along z
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real(DP) :: bg (3, 3), tau (3, nat), g (3, ngm)
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! input: reciprocal crystal basis vectors
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! input: the positions of the atoms in the c
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! input: the coordinates of the g vectors
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complex(DP) :: strf (ngm, ntyp), &
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eigts1 ( -nr1:nr1, nat), &
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eigts2 ( -nr2:nr2, nat), &
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eigts3 ( -nr3:nr3, nat)
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! output: the structure factor
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!
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! output: the phases e^{-iG\tau_s}
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!
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!
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! here the local variables
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!
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integer :: nt, na, ng, n1, n2, n3, ipol
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! counter over atom type
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! counter over atoms
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! counter over G vectors
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! counter over fft dimension along x
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! counter over fft dimension along y
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! counter over fft dimension along z
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! counter over polarizations
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real(DP) :: arg, bgtau (3)
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! the argument of the exponent
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! scalar product of bg and tau
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strf(:,:) = (0.d0,0.d0)
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do nt = 1, ntyp
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do na = 1, nat
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if (ityp (na) .eq.nt) then
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do ng = 1, ngm
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arg = (g (1, ng) * tau (1, na) + g (2, ng) * tau (2, na) &
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+ g (3, ng) * tau (3, na) ) * tpi
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strf (ng, nt) = strf (ng, nt) + CMPLX(cos (arg), -sin (arg),kind=DP)
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enddo
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endif
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enddo
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enddo
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do na = 1, nat
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do ipol = 1, 3
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bgtau (ipol) = bg (1, ipol) * tau (1, na) + &
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bg (2, ipol) * tau (2, na) + &
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bg (3, ipol) * tau (3, na)
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enddo
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do n1 = - nr1, nr1
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arg = tpi * n1 * bgtau (1)
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eigts1 (n1, na) = CMPLX(cos (arg), - sin (arg) ,kind=DP)
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enddo
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do n2 = - nr2, nr2
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arg = tpi * n2 * bgtau (2)
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eigts2 (n2, na) = CMPLX(cos (arg), - sin (arg) ,kind=DP)
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enddo
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do n3 = - nr3, nr3
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arg = tpi * n3 * bgtau (3)
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eigts3 (n3, na) = CMPLX(cos (arg), - sin (arg) ,kind=DP)
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enddo
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enddo
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return
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end subroutine struc_fact
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