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https://github.com/pfloos/quack
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53 lines
1.3 KiB
Fortran
53 lines
1.3 KiB
Fortran
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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 :: iG
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double precision :: Cx0
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double precision :: Cx1
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double precision :: rw
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double precision :: dExdw
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! Output variables
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double precision,intent(out) :: ExDD(nEns)
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! Weight-dependent Cx coefficient for RMFL20 exchange functional
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Cx0 = -(4d0/3d0)*(1d0/pi)**(1d0/3d0)
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Cx1 = -(176d0/105d0)*(1d0/pi)**(1d0/3d0)
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! Compute correlation energy for ground, singly-excited and doubly-excited states
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dExdw = 0d0
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do iG=1,nGrid
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rw = max(0d0,rhow(iG))
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if(rw > threshold) then
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dExdw = dExdw + weight(iG)*(Cx1 - Cx0)*rw**(4d0/3d0)
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end if
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end do
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ExDD(1) = - wEns(2) *dExdw
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ExDD(2) = (1d0 - wEns(2))*dExdw
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end subroutine RMFL20_lda_exchange_derivative_discontinuity
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