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https://github.com/pfloos/quack
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47 lines
1.0 KiB
Fortran
47 lines
1.0 KiB
Fortran
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subroutine US51_lda_exchange_individual_energy(nGrid,weight,rhow,rho,Ex)
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! Compute the restricted version of Slater's LDA exchange individual 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) :: 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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double precision,intent(in) :: rho(nGrid)
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! Local variables
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integer :: iG
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double precision :: r,rI,alpha
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double precision :: e,dedr
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! Output variables
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double precision,intent(out) :: Ex
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! Compute LDA exchange matrix in the AO basis
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alpha = -(3d0/2d0)*(3d0/(4d0*pi))**(1d0/3d0)
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Ex = 0d0
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do iG=1,nGrid
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r = max(0d0,rhow(iG))
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rI = max(0d0,rho(iG))
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if(r > threshold .or. rI > threshold) then
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e = alpha*r**(1d0/3d0)
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dedr = 1d0/3d0*alpha*r**(-2d0/3d0)
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Ex = Ex + weight(iG)*(e*rI + dedr*r*rI - dedr*r*r)
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endif
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enddo
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end subroutine US51_lda_exchange_individual_energy
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