2020-03-15 08:24:15 +01:00
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subroutine RMFL20_lda_exchange_energy(nEns,wEns,nGrid,weight,rho,Ex)
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2020-03-15 20:33:18 +01:00
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! Compute the restricted version of the Marut-Fromager-Loos weight-dependent exchange functional
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! The RMFL20 is a two-state, single-weight exchange functional
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2020-03-15 08:24:15 +01:00
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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) :: rho(nGrid)
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! Local variables
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integer :: iG
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2020-03-15 14:33:53 +01:00
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double precision :: Cx0
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double precision :: Cx1
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2020-03-15 08:24:15 +01:00
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double precision :: CxLDA
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double precision :: Cxw
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double precision :: r
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! Output variables
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double precision :: Ex
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! Cx coefficient for Slater LDA exchange
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2020-03-15 14:33:53 +01:00
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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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CxLDA = -(3d0/4d0)*(3d0/pi)**(1d0/3d0)
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2020-03-15 08:24:15 +01:00
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2020-03-15 14:33:53 +01:00
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Cxw = CxLDA + wEns(1)*(Cx1 - Cx0)
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2020-03-15 08:24:15 +01:00
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! Compute LDA exchange energy
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Ex = 0d0
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do iG=1,nGrid
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r = max(0d0,rho(iG))
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if(r > threshold) then
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Ex = Ex + weight(iG)*Cxw*r**(4d0/3d0)
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endif
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enddo
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end subroutine RMFL20_lda_exchange_energy
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