mirror of https://gitlab.com/QEF/q-e.git
116 lines
3.3 KiB
Fortran
116 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_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 : 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 : alat, omega, tpiba, tpiba2
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USE fft_base, ONLY : dfftp
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USE fft_interfaces, ONLY : fwfft
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USE gvect, ONLY : ngm, gstart, 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 scf, ONLY : rho, rho_core, rhog_core
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USE control_flags, ONLY : gamma_only
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USE noncollin_module, ONLY : noncolin
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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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! first the dummy variable
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!
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real(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(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(DP) :: arg, fact
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!
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forcecc(:,:) = 0.d0
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if ( ANY ( upf(1:ntyp)%nlcc ) ) go to 15
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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(dfftp%nnr,nspin) )
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!
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call v_xc (rho, rho_core, rhog_core, etxc, vtxc, vxc)
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!
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psic=(0.0_DP,0.0_DP)
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if (nspin == 1 .or. nspin == 4) then
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do ir = 1, dfftp%nnr
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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, dfftp%nnr
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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 fwfft ('Dense', psic, dfftp)
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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 ( upf(nt)%nlcc ) then
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call drhoc (ngl, gl, omega, tpiba2, rgrid(nt)%mesh, rgrid(nt)%r,&
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rgrid(nt)%rab, upf(nt)%rho_atc, 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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CMPLX( sin (arg), cos (arg) ,kind=DP) * 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 mp_sum( forcecc, intra_pool_comm )
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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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