mirror of https://gitlab.com/QEF/q-e.git
139 lines
5.3 KiB
Fortran
139 lines
5.3 KiB
Fortran
!
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! Copyright (C) 2002 FPMD 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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MODULE sic_module
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!------------------------------------------------------------------------------!
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!
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! The versions after 3.0 contain also the self-interaction-correction method
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! has proposed by Mauri et al. (PRB 2005), taking also into account the 'comment'
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! proposed by Sprik et al. (ICR 2005).
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! Thus, we introduce the parameters sic_alpha and sic_epsilon to correct the
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! exchange-correlation and the electronic hartree potentials, respectively.
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! They are two empirical parameters, thus to remain in a ab-initio
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! set them equal to 1.0d0.
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! Sprik et al. showed that, in same cases, i.e. OH radical, it should be better
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! to under estimate the correction to ex-ch, since in same way the exch already
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! corrects the electronic hartree part.
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! HOW AND WHEN USE THE SIC::
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! Fran's personal considerations:
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! the SIC is a way to correct the self-interaction WHEN
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! ONE and only ONE e- lives in an unpaired electronic level
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! we have choosen for it the spin up
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! Remember to select nspin == 2 and nelup = neldw + 1
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! the other e- are fictitious calculate in a LSD approach:
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! infact, even if the paired e- feel a different potential (for spin up and spin dw)
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! we constrain them to have the same force, and the same eigenvalues, the same eigenstates
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! When you applied this SIC scheme to a molecule or to an atom, which are neutral,
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! remember that you have to consider another correction to the energy level as proposed
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! by Landau: infact if you start from a neutral system and subtract the self-intereaction
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! the unpaired e- feels a charge system. Thus remeber a correction term ~2.317(Madelung)/2L_box
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USE kinds, ONLY: DP
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!
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IMPLICIT NONE
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SAVE
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INTEGER, ALLOCATABLE :: ind_localisation(:)
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INTEGER :: nat_localisation = 0
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LOGICAL :: print_localisation = .FALSE. ! Calculates hartree energy around specified atoms
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INTEGER :: self_interaction = 0
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REAL(DP) :: sic_epsilon = 0.0d0
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REAL(DP) :: sic_alpha = 0.0d0
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REAL(DP) :: sic_rloc = 0.0d0
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REAL(DP), ALLOCATABLE :: pos_localisation(:,:)
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!------------------------------------------------------------------------------!
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CONTAINS
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!------------------------------------------------------------------------------!
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SUBROUTINE sic_initval( nat_ , id_loc_ , sic_ , sic_epsilon_ , sic_alpha_, sic_rloc_ )
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IMPLICIT NONE
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INTEGER, INTENT(IN) :: nat_
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INTEGER, INTENT(IN) :: id_loc_ (:)
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CHARACTER(LEN=*), INTENT(IN) :: sic_
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REAL(DP), INTENT(IN) :: sic_epsilon_
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REAL(DP), INTENT(IN) :: sic_alpha_
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REAL(DP), INTENT(IN) :: sic_rloc_
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select case ( TRIM( sic_ ) )
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case ( 'sic_mac' )
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self_interaction = 2
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case default
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self_interaction = 0
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end select
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sic_epsilon = sic_epsilon_
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sic_alpha = sic_alpha_
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sic_rloc = sic_rloc_
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! counting the atoms around which i want to calculate the charge localization
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IF( ALLOCATED( ind_localisation ) ) DEALLOCATE( ind_localisation )
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ALLOCATE( ind_localisation( nat_ ) )
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ind_localisation( 1 : nat_ ) = id_loc_ ( 1 : nat_ )
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nat_localisation = COUNT( ind_localisation > 0 )
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IF( ALLOCATED( pos_localisation ) ) DEALLOCATE( pos_localisation )
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ALLOCATE( pos_localisation( 4, MAX( nat_localisation, 1 ) ) )
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!
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IF( nat_localisation > 0 ) print_localisation = .TRUE.
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!
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RETURN
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END SUBROUTINE sic_initval
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!------------------------------------------------------------------------------!
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SUBROUTINE deallocate_sic()
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IMPLICIT NONE
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IF( ALLOCATED( pos_localisation ) ) DEALLOCATE( pos_localisation )
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IF( ALLOCATED( ind_localisation ) ) DEALLOCATE( ind_localisation )
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RETURN
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END SUBROUTINE deallocate_sic
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!------------------------------------------------------------------------------!
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SUBROUTINE sic_info( )
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USE io_global, ONLY: stdout
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IMPLICIT NONE
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!
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! prints the type of USIC we will do :
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!
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IF( self_interaction == 0 ) THEN
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RETURN
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END IF
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WRITE(stdout, 591)
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WRITE(stdout, 592) self_interaction
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WRITE(stdout, 593)
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!!select case (self_interaction)
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IF ( self_interaction /= 0 ) THEN
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write(stdout,*) &
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' Unpaired-electron self-interaction correction by Mauri', self_interaction
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write(stdout,*) &
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' E_USIC_EHTE = U_hartree[rho_up + rho_dw]- sic_espilon * U_hartree[rho_up-rhp_down]'
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write(stdout,*) &
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' E_USIC_XC = E_xc[rho_up,rho_dw] - sic_alpha( E_xc[rho_up,rho_dw] + E_xc[rho_dw, rho_dw]) '
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END IF !!select
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591 FORMAT( 3X,'')
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592 FORMAT( 3X,'Introducing a Mauri Avezac Calandra Self_Interaction Correction: ', I3)
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593 FORMAT( 3X,'----------------------------------------')
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RETURN
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END SUBROUTINE sic_info
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!------------------------------------------------------------------------------!
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END MODULE sic_module
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!------------------------------------------------------------------------------!
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