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https://github.com/pfloos/quack
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51 lines
1.1 KiB
Fortran
51 lines
1.1 KiB
Fortran
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subroutine RMFL20_lda_exchange_energy(nEns,wEns,nGrid,weight,rho,Ex)
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! Compute restricted version of Marut-Fromager-Loos weight-dependent LDA exchange energy
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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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double precision :: CxLDA
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double precision :: Cx2
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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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CxLDA = -(4d0/3d0)*(1d0/pi)**(1d0/3d0)
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Cx2 = -(176d0/105d0)*(1d0/pi)**(1d0/3d0)
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Cxw = (1d0 - wEns(2))*CxLDA + wEns(2)*(Cx2 - CxLDA)
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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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