mirror of https://gitlab.com/QEF/q-e.git
107 lines
3.3 KiB
Fortran
107 lines
3.3 KiB
Fortran
!
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! Copyright (C) 2001-2007 Quantum ESPRESSO 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 force_corr (forcescc)
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!-----------------------------------------------------------------------
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! This routine calculates the force term vanishing at full
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! self-consistency. It follows the suggestion of Chan-Bohnen-Ho
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! (PRB 47, 4771 (1993)). The true charge density is approximated
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! by means of a free atom superposition.
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! (alessio f.)
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! Uses superposition of atomic charges contained in the array rho_at
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! and read from pseudopotential files
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!
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USE kinds, ONLY : DP
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USE constants, ONLY : tpi
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USE atom, ONLY : msh, rgrid
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USE uspp_param, ONLY : upf
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USE ions_base, ONLY : nat, ntyp => nsp, ityp, tau
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USE cell_base, ONLY : tpiba
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USE gvect, ONLY : ngm, gstart, nr1, nr2, nr3, nrx1, nrx2, &
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nrx3, nrxx, nl, g, ngl, gl, igtongl
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USE lsda_mod, ONLY : nspin
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USE scf, ONLY : vnew
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USE control_flags, ONLY : gamma_only
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USE wavefunctions_module, ONLY : psic
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USE mp_global, ONLY : intra_pool_comm
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USE mp, ONLY : mp_sum
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!
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implicit none
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!
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real(DP) :: forcescc (3, nat)
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!
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real(DP), allocatable :: rhocgnt (:), aux (:)
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! work space
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real(DP) :: gx, arg, fact
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! temp factors
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integer :: ir, isup, isdw, ig, nt, na, ipol, ndm
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! counters
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!
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! vnew is V_out - V_in, psic is the temp space
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!
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if (nspin == 1 .or. nspin == 4) then
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psic(:) = vnew%of_r (:, 1)
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else
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isup = 1
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isdw = 2
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psic(:) = (vnew%of_r (:, isup) + vnew%of_r (:, isdw)) * 0.5d0
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end if
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!
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ndm = MAXVAL ( msh(1:ntyp) )
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allocate ( aux(ndm), rhocgnt(ngl) )
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forcescc(:,:) = 0.d0
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call cft3 (psic, nr1, nr2, nr3, nrx1, nrx2, nrx3, - 1)
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if (gamma_only) then
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fact = 2.d0
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else
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fact = 1.d0
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end if
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do nt = 1, ntyp
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!
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! Here we compute the G.ne.0 term
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!
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do ig = gstart, ngl
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gx = sqrt (gl (ig) ) * tpiba
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do ir = 1, msh (nt)
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if (rgrid(nt)%r(ir) .lt.1.0d-8) then
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aux (ir) = upf(nt)%rho_at (ir)
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else
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aux (ir) = upf(nt)%rho_at (ir) * &
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sin(gx*rgrid(nt)%r(ir)) / (rgrid(nt)%r(ir)*gx)
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endif
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enddo
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call simpson (msh (nt), aux, rgrid(nt)%rab, rhocgnt (ig) )
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enddo
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do na = 1, nat
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if (nt.eq.ityp (na) ) then
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do ig = gstart, ngm
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arg = (g (1, ig) * tau (1, na) + g (2, ig) * tau (2, na) &
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+ g (3, ig) * tau (3, na) ) * tpi
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do ipol = 1, 3
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forcescc (ipol, na) = forcescc (ipol, na) + fact * &
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rhocgnt (igtongl(ig) ) * CMPLX(sin(arg),cos(arg),kind=DP) * &
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g(ipol,ig) * tpiba * CONJG(psic(nl(ig)))
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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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#ifdef __PARA
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call mp_sum( forcescc, intra_pool_comm )
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#endif
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deallocate ( aux, rhocgnt )
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return
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end subroutine force_corr
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