mirror of
https://github.com/pfloos/quack
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71 lines
1.3 KiB
Fortran
71 lines
1.3 KiB
Fortran
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subroutine elda_correlation_energy(nEns,aLF,nGrid,weight,rho,Ec)
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! Compute LDA correlation energy of 2-glomium for various states
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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) :: aLF(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,nspin)
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! Local variables
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integer :: iG
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double precision :: ra,rb,r,ec_p
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! Output variables
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double precision,intent(out) :: Ec(nsp)
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! Compute eLDA correlation energy
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Ec(:) = 0d0
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do iG=1,nGrid
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ra = max(0d0,rho(iG,1))
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rb = max(0d0,rho(iG,2))
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r = ra + rb
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! Spin-up contribution
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if(ra > threshold) then
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ec_p = aLF(1)/(1d0 + aLF(2)*ra**(-1d0/6d0) + aLF(3)*ra**(-1d0/3d0))
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Ec(1) = Ec(1) + weight(iG)*ec_p*ra
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end if
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! Opposite-spin contribution
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if(r > threshold) then
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ec_p = aLF(1)/(1d0 + aLF(2)*r**(-1d0/6d0) + aLF(3)*r**(-1d0/3d0))
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Ec(2) = Ec(2) + weight(iG)*ec_p*r
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end if
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! Spin-down contribution
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if(rb > threshold) then
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ec_p = aLF(1)/(1d0 + aLF(2)*rb**(-1d0/6d0) + aLF(3)*rb**(-1d0/3d0))
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Ec(3) = Ec(3) + weight(iG)*ec_p*rb
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end if
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end do
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Ec(2) = Ec(2) - Ec(1) - Ec(3)
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end subroutine elda_correlation_energy
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