2020-04-06 19:40:42 +02:00
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subroutine RGIC_lda_exchange_energy(nEns,wEns,nGrid,weight,rho,Ex)
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! Compute the restricted version of the GIC exchange functional
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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 :: r
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double precision :: a,b,c,w
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double precision :: CxGIC
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! Output variables
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double precision :: Ex
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2020-04-09 14:31:50 +02:00
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! Weight-dependent Cx coefficient
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2020-04-06 19:40:42 +02:00
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2020-04-09 14:31:50 +02:00
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! Parameters for H2 at equilibrium
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! a = + 0.5751782560799208d0
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! b = - 0.021108186591137282d0
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! c = - 0.36718902716347124d0
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! Parameters for stretch H2
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2020-04-09 21:58:10 +02:00
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! a = + 0.01922622507087411d0
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! b = - 0.01799647558018601d0
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! c = - 0.022945430666782573d0
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2020-04-09 14:31:50 +02:00
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! Parameters for He
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2020-04-09 21:58:10 +02:00
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a = 1.9125735895875828d0
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b = 2.715266992840757d0
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c = 2.1634223380633086d0
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2020-04-06 19:40:42 +02:00
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w = wEns(2)
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2020-04-06 22:27:13 +02:00
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CxGIC = 1d0 - w*(1d0 - w)*(a + b*(w - 0.5d0) + c*(w - 0.5d0)**2)
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CxGIC = CxLDA*CxGIC
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2020-04-06 19:40:42 +02:00
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! Compute GIC-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)*CxGIC*r**(4d0/3d0)
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endif
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enddo
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end subroutine RGIC_lda_exchange_energy
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