mirror of https://github.com/pfloos/quack
57 lines
1009 B
Fortran
57 lines
1009 B
Fortran
subroutine CCSD_Ec_nc(nO,nV,t1,t2,Fov,OOVV,EcCCSD)
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! Compute the CCSD correlatio energy in non-canonical form
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implicit none
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! Input variables
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integer,intent(in) :: nO,nV
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double precision,intent(in) :: t1(nO,nV)
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double precision,intent(in) :: t2(nO,nO,nV,nV)
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double precision,intent(in) :: Fov(nO,nV)
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double precision,intent(in) :: OOVV(nO,nO,nV,nV)
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! Local variables
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integer :: i,j,a,b
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! Output variables
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double precision,intent(out) :: EcCCSD
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! Compute CCSD correlation energy
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EcCCSD = 0d0
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! Singles contribution
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do i=1,nO
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do a=1,nV
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EcCCSD = EcCCSD + Fov(i,a)*t1(i,a)
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end do
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end do
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! Doubles contribution
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do i=1,nO
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do j=1,nO
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do a=1,nV
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do b=1,nV
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EcCCSD = EcCCSD &
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+ 0.5d0*OOVV(i,j,a,b)*t1(i,a)*t1(j,b) &
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+ 0.25d0*OOVV(i,j,a,b)*t2(i,j,a,b)
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end do
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end do
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end do
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end do
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end subroutine
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