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59 lines
1.4 KiB
Fortran
59 lines
1.4 KiB
Fortran
subroutine RMFL20_lda_exchange_derivative_discontinuity(nEns,wEns,nGrid,weight,rhow,ExDD)
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! Compute the restricted version of the eLDA exchange part of the derivative discontinuity
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implicit none
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include 'parameters.h'
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! Input variables
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integer,intent(in) :: nEns
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double precision,intent(in) :: wEns(nEns)
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integer,intent(in) :: nGrid
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double precision,intent(in) :: weight(nGrid)
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double precision,intent(in) :: rhow(nGrid)
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! Local variables
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integer :: iEns,jEns
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integer :: iG
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double precision :: r
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double precision :: dExdw(nEns)
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double precision,external :: Kronecker_delta
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double precision,parameter :: Cx0 = - (4d0/3d0)*(1d0/pi)**(1d0/3d0)
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double precision,parameter :: Cx1 = - (176d0/105d0)*(1d0/pi)**(1d0/3d0)
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! Output variables
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double precision,intent(out) :: ExDD(nEns)
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! Compute correlation energy for ground- and doubly-excited states
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dExdw(:) = 0d0
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do iG=1,nGrid
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r = max(0d0,rhow(iG))
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if(r > threshold) then
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dExdw(1) = 0d0
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dExdw(2) = dExdw(2) + weight(iG)*(Cx1 - Cx0)*r**(4d0/3d0)
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end if
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end do
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ExDD(:) = 0d0
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do iEns=1,nEns
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do jEns=2,nEns
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ExDD(iEns) = ExDD(iEns) + (Kronecker_delta(iEns,jEns) - wEns(jEns))*dExdw(jEns)
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end do
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end do
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end subroutine RMFL20_lda_exchange_derivative_discontinuity
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