mirror of https://gitlab.com/QEF/q-e.git
145 lines
4.2 KiB
Fortran
145 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 dv_of_drho_vdw (mode, dvscf, flag)
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!-----------------------------------------------------------------------
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!
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! This routine computes the change of the self consistent potential
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! due to the perturbation.
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!
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USE funct, ONLY : dft_is_gradient, dmxc
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USE pwcom
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USE scf, ONLY : rho, rho_core
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USE kinds, ONLY : DP
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USE phcom
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USE eff_v, ONLY : rho_veff
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IMPLICIT NONE
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INTEGER :: mode
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! input: the mode to do
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COMPLEX(kind=DP) :: dvscf (nrxx, nspin)
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! input: the change of the charge,
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! output: change of the potential
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LOGICAL :: flag
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! input: if true add core charge
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INTEGER :: ir, is, is1, ig
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! counter on r vectors
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! counter on spin polarizations
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! counter on g vectors
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real(kind=DP) :: qg2, fac, ttd
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! the modulus of (q+G)^2
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! the structure factor
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! constant 2/3
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COMPLEX(kind=DP), ALLOCATABLE :: dvaux (:,:), drhoc (:),&
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dv_tfvw (:,:)
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! auxiliary variable for potential
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! the change of the core charge
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! auxiliary variable for derivation of charge density
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!
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real(kind=dp) :: rhotot
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!
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CALL start_clock ('dv_of_drho')
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ALLOCATE (dvaux( nrxx, nspin), dv_tfvw( nrxx, nspin))
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ALLOCATE (drhoc( nrxx))
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!
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dv_tfvw = dvscf
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!
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! the exchange-correlation contribution is computed in real space
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!
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dvaux (:,:) = (0.d0, 0.d0)
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fac = 1.d0 / dble (nspin)
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IF (nlcc_any.and.flag) THEN
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CALL addcore (mode, drhoc)
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DO is = 1, nspin
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rho%of_r(:, is) = rho%of_r(:, is) + fac * rho_core (:)
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dvscf(:, is) = dvscf(:, is) + fac * drhoc (:)
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ENDDO
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ENDIF
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! allocate ( dmuxc(nrxx, nspin, nspin) )
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dmuxc(:,:,:) = 0.d0
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DO ir = 1, nrxx
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rhotot = rho%of_r (ir, nspin) + rho_core (ir)
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IF (rhotot>1.d-30) dmuxc (ir, 1, 1) = dmxc (rhotot)
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IF (rhotot< - 1.d-30) dmuxc (ir, 1, 1) = - dmxc ( - rhotot)
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ENDDO
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DO is = 1, nspin
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DO is1 = 1, nspin
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DO ir = 1, nrxx
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dvaux(ir,is) = dvaux(ir,is) + dmuxc(ir,is,is1) * dvscf(ir,is1)
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ENDDO
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ENDDO
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ENDDO
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! deallocate ( dmuxc )
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!
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! add gradient correction to xc, NB: if nlcc is true we need to add here
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! its contribution. grho contains already the core charge
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!
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! if (igcx /= 0 .or. igcc /= 0) call dgradcorr &
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! (rho%of_r, grho, dvxc_rr, dvxc_sr, dvxc_ss, dvxc_s, xq, &
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! dvscf, nr1, nr2, nr3, nrx1, nrx2, nrx3, nrxx, nspin, nl, ngm, g, &
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! alat, omega, dvaux)
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IF (nlcc_any.and.flag) THEN
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DO is = 1, nspin
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rho%of_r(:, is) = rho%of_r(:, is) - fac * rho_core (:)
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dvscf(:, is) = dvscf(:, is) - fac * drhoc (:)
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ENDDO
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ENDIF
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!
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! copy the total (up+down) delta rho in dvscf(*,1) and go to G-space
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!
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IF (nspin == 2) THEN
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dvscf(:,1) = dvscf(:,1) + dvscf(:,2)
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ENDIF
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!
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CALL cft3 (dvscf, nr1, nr2, nr3, nrx1, nrx2, nrx3, -1)
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!
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! hartree contribution is computed in reciprocal space
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!
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DO is = 1, nspin
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CALL cft3 (dvaux (1, is), nr1, nr2, nr3, nrx1, nrx2, nrx3, - 1)
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DO ig = 1, ngm
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qg2 = (g(1,ig)+xq(1))**2 + (g(2,ig)+xq(2))**2 + (g(3,ig)+xq(3))**2
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IF (qg2 > 1.d-8) THEN
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dvaux(nl(ig),is) = dvaux(nl(ig),is) + &
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e2 * fpi * dvscf(nl(ig),1) / (tpiba2 * qg2)
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! dvaux(nl(ig),is) = e2 * fpi * dvscf(nl(ig),1) / (tpiba2 * qg2)
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ENDIF
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ENDDO
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!
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! and transformed back to real space
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!
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CALL cft3 (dvaux (1, is), nr1, nr2, nr3, nrx1, nrx2, nrx3, +1)
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ENDDO
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!
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! TFvW contribution is computed in real space
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!
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ttd = 2.d0/3.d0
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is = 1
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dv_tfvw(:, is) = ttd * (0.125d0/ttd*fpi**2)**ttd * dv_tfvw (:, is) &
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* ( abs(rho_veff(:,is))** (-ttd/2.d0) )
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! dv_tfvw(:, is) = ttd * (0.125d0/ttd*fpi**2)**ttd * dv_tfvw (:, is) &
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! * ( abs(rhof_r(:,is)+rho_core(:))** (-ttd/2.d0) )
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!
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! at the end the three contributes are added
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!
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dvscf (:,:) = dvaux (:,:) + dv_tfvw (:,:)
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!
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DEALLOCATE (drhoc)
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DEALLOCATE (dvaux)
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CALL stop_clock ('dv_of_drho')
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RETURN
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END SUBROUTINE dv_of_drho_vdw
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