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https://github.com/pfloos/quack
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42 lines
846 B
Fortran
42 lines
846 B
Fortran
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subroutine fock_exchange_individual_energy(nBas,P,ERI,Ex)
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! Compute the Fock exchange potential
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implicit none
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! Input variables
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integer,intent(in) :: nBas
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double precision,intent(in) :: P(nBas,nBas)
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double precision,intent(in) :: ERI(nBas,nBas,nBas,nBas)
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! Local variables
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integer :: mu,nu,la,si
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double precision,allocatable :: Fx(:,:)
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double precision,external :: trace_matrix
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! Output variables
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double precision,intent(out) :: Ex
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! Compute HF exchange matrix
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allocate(Fx(nBas,nBas))
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Fx(:,:) = 0d0
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do si=1,nBas
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do la=1,nBas
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do nu=1,nBas
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do mu=1,nBas
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Fx(mu,nu) = Fx(mu,nu) + P(la,si)*ERI(mu,la,si,nu)
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enddo
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enddo
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enddo
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enddo
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Ex = -0.25d0*trace_matrix(nBas,matmul(P,Fx))
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end subroutine fock_exchange_individual_energy
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