mirror of https://gitlab.com/QEF/q-e.git
143 lines
4.2 KiB
Fortran
143 lines
4.2 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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#include "f_defs.h"
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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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USE kinds, ONLY : DP
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USE parameters, ONLY : nchix
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USE atom, ONLY : nchi, lchi, chi, oc, r, rab, msh
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USE constants, ONLY : tpi, fpi
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USE cell_base, ONLY : omega, tpiba
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USE ions_base, ONLY : nat, ntyp => nsp, ityp, tau
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USE basis, ONLY : natomwfc
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USE gvect, ONLY : ig1, ig2, ig3, eigts1, eigts2, eigts3, g
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USE klist, ONLY : xk
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USE wvfct, ONLY : npwx, npw, nbnd, igk
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USE us, ONLY : tab_at, dq
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!
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implicit none
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!
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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, na, m, lm, ig, iig, &
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i0, i1, i2, i3
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!
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real(kind=DP), allocatable :: qg(:), 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, px, ux, vx, wx
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complex(kind=DP) :: kphase , lphase
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call start_clock ('atomic_wfc')
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allocate ( qg(npw), chiq(npw,nchix,ntyp), gk(3,npw), 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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qg(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, qg, 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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qg(ig) = sqrt(qg(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 ( oc (nb, nt) >= 0.d0) then
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do ig = 1, npw
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px = qg (ig) / dq - int (qg (ig) / dq)
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ux = 1.d0 - px
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vx = 2.d0 - px
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wx = 3.d0 - px
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i0 = qg (ig) / dq + 1
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i1 = i0 + 1
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i2 = i0 + 2
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i3 = i0 + 3
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chiq (ig, nb, nt) = &
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tab_at (i0, nb, nt) * ux * vx * wx / 6.d0 + &
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tab_at (i1, nb, nt) * px * vx * wx / 2.d0 - &
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tab_at (i2, nb, nt) * px * ux * wx / 2.d0 + &
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tab_at (i3, nb, nt) * px * ux * vx / 6.d0
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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) + 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), na) * &
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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 (oc (nb, nt) >= 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 errore ('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 errore ('atomic_wfc', &
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'something wrong', 1)
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deallocate(qg, chiq ,gk, 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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