mirror of https://gitlab.com/QEF/q-e.git
149 lines
4.4 KiB
Fortran
149 lines
4.4 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 atomic_wfc (ik, wfcatom)
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!-----------------------------------------------------------------------
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!
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! This routine computes the superposition of atomic wavefunctions for a
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! given k-point.
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!
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#include "machine.h"
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use pwcom
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implicit none
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integer :: ik
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! input: k-point
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complex(kind=DP) :: wfcatom (npwx, natomwfc) ! output: atomic wavefunctions
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!
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integer :: n_starting_wfc, lmax_wfc, nt, l, nb, ir, na, m, lm, ig, iig, nw
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!
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real(kind=DP), allocatable :: q (:), ylm (:,:), chiq (:,:,:), aux (:), &
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gk (:,:), vchi (:)
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complex(kind=DP), allocatable :: sk (:)
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real(kind=DP) :: vqint, arg
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complex(kind=DP) :: kphase , lphase
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call start_clock ('atomic_wfc')
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allocate (q(npw),chiq(npw,nchix,ntyp),gk(3,npw),aux(ndm),vchi(ndm),sk(npw))
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! calculate max angular momentum required in wavefunctions
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lmax_wfc = 0
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do nt = 1, ntyp
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do nb = 1, nchi (nt)
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lmax_wfc = max (lmax_wfc, lchi (nb, nt) )
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enddo
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enddo
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!
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allocate(ylm (npw,(lmax_wfc+1)**2) )
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!
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do ig = 1, npw
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gk (1,ig) = xk(1, ik) + g(1, igk(ig) )
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gk (2,ig) = xk(2, ik) + g(2, igk(ig) )
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gk (3,ig) = xk(3, ik) + g(3, igk(ig) )
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q (ig) = gk(1, ig)**2 + gk(2, ig)**2 + gk(3, ig)**2
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enddo
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!
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! ylm = spherical harmonics
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!
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call ylmr2 ((lmax_wfc+1)**2, npw, gk, q, ylm)
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!
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! set now q=|k+G| in atomic units
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!
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do ig = 1, npw
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q (ig) = sqrt(q(ig))*tpiba
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enddo
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!
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n_starting_wfc = 0
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!
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! chiq = radial fourier transform of atomic orbitals chi
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!
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do nt = 1, ntyp
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do nb = 1, nchi (nt)
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if (.not.newpseudo (nt) .or.oc (nb, nt) .gt.0.d0) then
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l = lchi (nb, nt)
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!
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! here the first term
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!
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call sph_bes (msh (nt), r (1, nt), q (1), l, aux)
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do ir = 1, msh (nt)
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vchi (ir) = chi (ir, nb, nt) * aux (ir) * r (ir, nt)
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enddo
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call simpson (msh (nt), vchi, rab (1, nt), vqint)
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chiq (1, nb, nt) = vqint
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!
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! here the other terms
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!
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do ig = 2, npw
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! dirty trick to speed up calculation:
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! do not recalculate if |k+G_i|=|k+G_{i-1}|
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if (abs (q (ig) - q (ig - 1) ) .gt.1.0d-8) then
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call sph_bes (msh (nt), r (1, nt), q (ig), l, aux)
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do ir = 1, msh (nt)
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vchi (ir) = chi (ir, nb, nt) * aux (ir) * r (ir, nt)
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enddo
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call simpson (msh (nt), vchi, rab (1, nt), vqint)
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endif
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chiq (ig, nb, nt) = vqint
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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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arg = (xk (1, ik) * tau (1, na) + xk (2, ik) * tau (2, na) &
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+ xk (3, ik) * tau (3, na) ) * tpi
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kphase = DCMPLX (cos (arg), - sin (arg) )
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!
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! sk is the structure factor
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!
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do ig = 1, npw
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iig = igk (ig)
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sk (ig) = kphase * eigts1 (ig1 (iig), na) * eigts2 (ig2 (iig), &
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na) * eigts3 (ig3 (iig), na)
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enddo
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!
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nt = ityp (na)
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do nb = 1, nchi (nt)
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if (.not.newpseudo (nt) .or.oc (nb, nt) .gt.0.d0) then
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l = lchi (nb, nt)
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lphase = (0.d0,1.d0)**l
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! the factor i^l MUST BE PRESENT in order to produce
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! wavefunctions for k=0 that are real in real space
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do m = 1, 2 * l + 1
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lm = l**2 + m
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n_starting_wfc = n_starting_wfc + 1
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if (n_starting_wfc.gt.natomwfc) &
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call error ('atomic_wfc', 'too many wfcs', 1)
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do ig = 1, npw
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wfcatom (ig, n_starting_wfc) = lphase * &
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sk (ig) * ylm (ig, lm) * chiq (ig, nb, nt)
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enddo
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enddo
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endif
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enddo
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enddo
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if (n_starting_wfc.ne.natomwfc) call error ('atomic_wfc', &
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'something wrong', 1)
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! normalize atomic wfcs (not a bad idea in general and necessary to
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! compute correctly lda+U projections)
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do nw = 1,natomwfc
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call DSCAL(2*npw,fpi/sqrt(omega),wfcatom(1,nw),1)
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end do
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deallocate(q, chiq ,gk ,aux ,vchi ,sk ,ylm)
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call stop_clock ('atomic_wfc')
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return
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end subroutine atomic_wfc
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