2020-04-06 19:40:42 +02:00
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subroutine RGIC_lda_exchange_derivative_discontinuity(nEns,wEns,nGrid,weight,rhow,ExDD)
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! Compute the restricted version of the GIC 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) :: 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) :: rhow(nGrid)
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! Local variables
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integer :: iEns,jEns
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integer :: iG
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double precision :: r
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2020-04-06 23:34:49 +02:00
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double precision,allocatable :: dExdw(:)
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2020-04-06 19:40:42 +02:00
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double precision,external :: Kronecker_delta
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double precision :: a,b,c,w
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double precision :: dCxGICdw
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! Output variables
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double precision,intent(out) :: ExDD(nEns)
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2020-04-06 23:34:49 +02:00
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! Memory allocation
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allocate(dExdw(nEns))
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2020-04-27 23:04:00 +02:00
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! Weight-dependent Cx coefficient for RMFL20 exchange functional
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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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2020-04-27 23:04:00 +02:00
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a = + 0.5739189000851961d0
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b = - 0.0003469882157336496d0
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c = - 0.2676338054343272d0
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2020-04-09 14:31:50 +02:00
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! Parameters for stretch H2
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2020-04-27 23:04:00 +02:00
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! a = + 0.01918229168254928d0
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! b = - 0.01545313842512261d0
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! c = - 0.012720073519142448d0
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2020-04-09 14:31:50 +02:00
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! Parameters for He
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2020-04-27 23:04:00 +02:00
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! a = 1.9015719148496788d0
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! b = 2.5236598782764412d0
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! c = 1.6652282199359842d0
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2020-04-06 19:40:42 +02:00
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2020-04-26 23:17:27 +02:00
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w = 0.5d0*wEns(2) + wEns(3)
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2020-04-09 14:31:50 +02:00
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dCxGICdw = (0.5d0*b + (2d0*a + 0.5d0*c)*(w - 0.5d0) - (1d0 - w)*w*(3d0*b + 4d0*c*(w - 0.5d0)))
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2020-04-06 22:27:13 +02:00
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dCxGICdw = CxLDA*dCxGICdw
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2020-04-06 19:40:42 +02:00
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dExdw(:) = 0d0
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do iG=1,nGrid
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r = max(0d0,rhow(iG))
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if(r > threshold) then
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dExdw(1) = 0d0
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2020-04-26 23:17:27 +02:00
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dExdw(2) = dExdw(2) + 0.5d0*weight(iG)*dCxGICdw*r**(4d0/3d0)
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dExdw(3) = dExdw(3) + 1.0d0*weight(iG)*dCxGICdw*r**(4d0/3d0)
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2020-04-06 19:40:42 +02:00
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end if
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end do
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2020-04-06 23:34:49 +02:00
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ExDD(:) = 0d0
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2020-04-06 19:40:42 +02:00
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do iEns=1,nEns
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do jEns=2,nEns
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ExDD(iEns) = ExDD(iEns) + (Kronecker_delta(iEns,jEns) - wEns(jEns))*dExdw(jEns)
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end do
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end do
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end subroutine RGIC_lda_exchange_derivative_discontinuity
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