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QuAcK/src/eDFT/UCC_lda_exchange_energy.f90

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subroutine UCC_lda_exchange_energy(nEns,wEns,nCC,aCC,nGrid,weight,rho,Cx_choice,doNcentered,Ex)
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! Compute the unrestricted version of the curvature-corrected exchange functional
implicit none
include 'parameters.h'
! Input variables
integer,intent(in) :: nEns
double precision,intent(in) :: wEns(nEns)
integer,intent(in) :: nCC
double precision,intent(in) :: aCC(nCC,nEns-1)
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integer,intent(in) :: nGrid
double precision,intent(in) :: weight(nGrid)
double precision,intent(in) :: rho(nGrid)
integer,intent(in) :: Cx_choice
logical,intent(in) :: doNcentered
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! Local variables
integer :: iG
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double precision :: r
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double precision :: a1,b1,c1,w1
double precision :: a2,b2,c2,w2
double precision :: Fx1,Fx2,Cx
! Output variables
double precision :: Ex
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! Parameters for first state
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a1 = aCC(1,1)
b1 = aCC(2,1)
c1 = aCC(3,1)
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! Parameters for second state
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a2 = aCC(1,2)
b2 = aCC(2,2)
c2 = aCC(3,2)
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! Defining enhancements factor for weight-dependent functionals
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if(doNcentered) then
w1 = wEns(2)
Fx1 = 1d0 - w1*(2d0 - w1)*(a1 + b1*(w1 - 1d0) + c1*(w1 - 1d0)**2)
w2 = wEns(3)
Fx2 = 1d0 - w2*(2d0 - w2)*(a2 + b2*(w2 - 1d0) + c2*(w2 - 1d0)**2)
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else
w1 = wEns(2)
Fx1 = 1d0 - w1*(1d0 - w1)*(a1 + b1*(w1 - 0.5d0) + c1*(w1 - 0.5d0)**2)
w2 = wEns(3)
Fx2 = 1d0 - w2*(1d0 - w2)*(a2 + b2*(w2 - 0.5d0) + c2*(w2 - 0.5d0)**2)
endif
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select case (Cx_choice)
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case(1)
Cx = CxLSDA*Fx1
case(2)
Cx = CxLSDA*Fx2
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case(3)
Cx = CxLSDA*Fx2*Fx1
case default
Cx = CxLSDA
end select
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! Compute GIC-LDA exchange energy
Ex = 0d0
do iG=1,nGrid
r = max(0d0,rho(iG))
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if(r > threshold) Ex = Ex + weight(iG)*Cx*r**(4d0/3d0)
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enddo
end subroutine UCC_lda_exchange_energy