2020-03-15 14:33:53 +01:00
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subroutine RMFL20_lda_exchange_potential(nEns,wEns,nGrid,weight,nBas,AO,rho,Fx)
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! Compute the restricted version of the weight-dependent MFL20 exchange potential
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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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integer,intent(in) :: nBas
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double precision,intent(in) :: AO(nBas,nGrid)
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double precision,intent(in) :: rho(nGrid)
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! Local variables
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integer :: mu,nu,iG
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double precision :: Cx0
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double precision :: Cx1
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double precision :: CxLDA
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double precision :: Cxw
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double precision :: r,vAO
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! Output variables
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double precision,intent(out) :: Fx(nBas,nBas)
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2020-03-17 11:29:20 +01:00
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! Weight-dependent Cx coefficient for RMFL20 exchange functional
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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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2020-03-17 11:29:20 +01:00
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Cxw = CxLDA + wEns(2)*(Cx1 - Cx0)
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2020-03-15 14:33:53 +01:00
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! Compute LDA exchange matrix in the AO basis
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Fx(:,:) = 0d0
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do mu=1,nBas
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do nu=1,nBas
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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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vAO = weight(iG)*AO(mu,iG)*AO(nu,iG)
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Fx(mu,nu) = Fx(mu,nu) + vAO*4d0/3d0*Cxw*r**(1d0/3d0)
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endif
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enddo
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enddo
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enddo
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end subroutine RMFL20_lda_exchange_potential
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