mirror of https://gitlab.com/QEF/q-e.git
141 lines
4.2 KiB
Fortran
141 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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!
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!-----------------------------------------------------------------------
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subroutine set_rhoc
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!-----------------------------------------------------------------------
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!
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! This routine compute the core charge on the real space 3D mesh
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!
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!
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#include "machine.h"
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use pwcom
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use gamma
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use allocate
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implicit none
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!
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real(kind=DP), parameter :: eps = 1.d-10
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complex(kind=DP) , pointer :: aux (:)
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! work space used for the fft of the core charge
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real(kind=DP) , pointer :: rhocg(:)
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! the radial fourier trasform
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real(kind=DP) :: rhoima, rhoneg, rhorea
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! used to check the core charge
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real(kind=DP) , pointer :: dum(:,:)
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! work array containing rho=0
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real(kind=DP) :: vtxcc
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! dummy xc energy term
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integer :: ir, nt, ng
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! counter on mesh points
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! counter on atomic types
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! counter on g vectors
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logical :: no_core_only
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! if .f. subtract etxcc from etot
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etxcc = 0.d0
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do nt = 1, ntyp
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if (nlcc (nt) ) goto 10
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enddo
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call setv (nrxx, 0.d0, rho_core, 1)
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return
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10 continue
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call mallocate(aux, nrxx)
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call mallocate(rhocg, ngl)
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call setv (2 * nrxx, 0.d0, aux, 1)
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!
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! the sum is on atom types
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!
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do nt = 1, ntyp
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if (nlcc (nt) ) then
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!
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! drhoc compute the radial fourier transform for each shell of g vec
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!
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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), msh (nt), r (1, nt), rab (1, nt), &
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rho_atc (1, nt), rhocg)
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!
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! multiply by the structure factor and sum
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!
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do ng = 1, ngm
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aux (nl (ng) ) = aux (nl (ng) ) + strf (ng, nt) * rhocg (igtongl(ng))
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enddo
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endif
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enddo
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do ng = 1, ngm
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aux(nlm(ng)) = conjg(aux(nl (ng)))
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end do
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!
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! the core charge in real space
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!
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call cft3 (aux, nr1, nr2, nr3, nrx1, nrx2, nrx3, 1)
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!
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! test on the charge and computation of the core energy
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!
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rhoneg = 0.d0
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rhoima = 0.d0
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do ir = 1, nrxx
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rhoneg = rhoneg + min (0.d0, DREAL (aux (ir) ) )
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rhoima = rhoima + abs (DIMAG (aux (ir) ) )
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rhorea = max (DREAL (aux (ir) ), eps)
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rho_core(ir) = DREAL (aux(ir))
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!
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! NOTE: Core charge is computed in reciprocal space and brought to real
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! space by FFT. For non smooth core charges (or insufficient cut-off)
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! this may result in negative values in some grid points.
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! Up to October 1999 the core charge was forced to be positive definite.
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! This induces an error in the force, and probably stress, calculation i
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! the number of grid points where the core charge would be otherwise neg
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! is large. The error disappears for sufficiently high cut-off, but may
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! rather large and it is better to leave the core charge as it is.
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! If you insist to have it positive definite (with the possible problems
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! mentioned above) uncomment the following line. SdG, Oct 15 1999
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!
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! rho_core(ir) = rhorea
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!
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enddo
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rhoneg = rhoneg / (nr1 * nr2 * nr3)
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rhoima = rhoima / (nr1 * nr2 * nr3)
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#ifdef PARA
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call reduce (1, rhoneg)
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call reduce (1, rhoima)
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#endif
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if (rhoneg.lt. - 1.0d-6.or.rhoima.gt.1.0d-6) &
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write (6, '(" warning: negative or imaginary core charge ",2f12.6)')&
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rhoneg, rhoima
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!
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no_core_only = .true.
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if (no_core_only) then
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etxcc = 0.d0
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else
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!
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! calculate core_only exch-corr energy etxcc=E_xc[rho_core] if required
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! This term is present only for compatibility with previous versions
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!
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call mallocate(dum,nrxx , nspin)
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call setv (nspin * nrxx, 0.d0, dum, 1)
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call v_xc (dum, rho_core, nr1, nr2, nr3, nrx1, nrx2, nrx3, &
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nrxx, nl, ngm, g, nspin, alat, omega, etxcc, vtxcc, aux)
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call mfree(dum)
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write (6, 9000) etxcc
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write (6, * ) 'BEWARE it will be subtracted from total energy !'
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endif
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call mfree (rhocg)
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call mfree (aux)
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!
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return
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9000 format (5x,'core-only xc energy = ',f15.8,' ryd')
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end subroutine set_rhoc
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