mirror of https://gitlab.com/QEF/q-e.git
117 lines
3.3 KiB
Fortran
117 lines
3.3 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 force_cc (forcecc)
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!----------------------------------------------------------------------
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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 : rho_atc, numeric, mesh, r, rab, nlcc
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USE ions_base, ONLY : nat, ntyp => nsp, ityp, tau
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USE cell_base, ONLY : alat, omega, tpiba, tpiba2
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USE gvect, ONLY : ngm, gstart, nr1, nr2, nr3, nrx1, nrx2, &
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nrx3, nrxx, nl, g, gg, ngl, gl, igtongl
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USE ener, ONLY : etxc, vtxc
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USE lsda_mod, ONLY : nspin
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USE pseud, ONLY : a_nlcc, b_nlcc, alpha_nlcc
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USE scf, ONLY : rho, rho_core
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USE wvfct, ONLY : gamma_only
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USE wavefunctions_module, ONLY : psic
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!
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implicit none
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!
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! first the dummy variable
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!
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real(kind=DP) :: forcecc (3, nat)
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! output: the local forces on atoms
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integer :: ipol, ig, ir, nt, na
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! counter on polarizations
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! counter on G vectors
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! counter on FFT grid points
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! counter on types of atoms
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! counter on atoms
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real(kind=DP), allocatable :: vxc (:,:), rhocg (:)
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! exchange-correlation potential
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! radial fourier trasform of rho core
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real(kind=DP) :: arg, fact
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!
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forcecc(:,:) = 0.d0
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do nt = 1, ntyp
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if (nlcc (nt) ) goto 15
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enddo
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return
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!
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15 continue
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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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!
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! recalculate the exchange-correlation potential
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!
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allocate ( vxc(nrxx,nspin) )
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!
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call v_xc (rho, rho_core, nr1, nr2, nr3, nrx1, nrx2, nrx3, nrxx, &
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nl, ngm, g, nspin, alat, omega, etxc, vtxc, vxc)
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!
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if (nspin == 1 .or. nspin == 4) then
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do ir = 1, nrxx
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psic (ir) = vxc (ir, 1)
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enddo
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else
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do ir = 1, nrxx
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psic (ir) = 0.5d0 * (vxc (ir, 1) + vxc (ir, 2) )
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enddo
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endif
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deallocate (vxc)
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call cft3 (psic, nr1, nr2, nr3, nrx1, nrx2, nrx3, - 1)
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!
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! psic contains now Vxc(G)
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!
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allocate ( rhocg(ngl) )
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!
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! core correction term: sum on g of omega*ig*exp(-i*r_i*g)*n_core(g)*vxc
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! g = 0 term gives no contribution
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!
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do nt = 1, ntyp
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if (nlcc (nt) ) then
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call drhoc (ngl, gl, omega, tpiba2, numeric (nt), a_nlcc (nt), &
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b_nlcc (nt), alpha_nlcc (nt), mesh (nt), r (1, nt), rab (1, nt), &
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rho_atc (1, nt), rhocg)
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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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forcecc (ipol, na) = forcecc (ipol, na) + tpiba * omega * &
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rhocg (igtongl (ig) ) * conjg (psic (nl (ig) ) ) * &
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DCMPLX ( sin (arg), cos (arg) ) * g (ipol, ig) * fact
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enddo
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enddo
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endif
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enddo
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endif
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enddo
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#ifdef __PARA
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call reduce (3 * nat, forcecc)
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#endif
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deallocate (rhocg)
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!
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return
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end subroutine force_cc
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