10
1
mirror of https://github.com/pfloos/quack synced 2024-12-24 13:23:38 +01:00
QuAcK/src/CC/CCSD_Ec_nc.f90

57 lines
1019 B
Fortran

subroutine CCSD_Ec_nc(nO,nV,t1,t2,Fov,OOVV,EcCCSD)
! Compute the CCSD correlatio energy in non-conanical form
implicit none
! Input variables
integer,intent(in) :: nO,nV
double precision,intent(in) :: t1(nO,nV)
double precision,intent(in) :: t2(nO,nO,nV,nV)
double precision,intent(in) :: Fov(nO,nV)
double precision,intent(in) :: OOVV(nO,nO,nV,nV)
! Local variables
integer :: i,j,a,b
! Output variables
double precision,intent(out) :: EcCCSD
! Compute CCSD correlation energy
EcCCSD = 0d0
! Singles contribution
do i=1,nO
do a=1,nV
EcCCSD = EcCCSD + Fov(i,a)*t1(i,a)
end do
end do
! Doubles contribution
do i=1,nO
do j=1,nO
do a=1,nV
do b=1,nV
EcCCSD = EcCCSD &
+ 0.5d0*OOVV(i,j,a,b)*t1(i,a)*t1(j,b) &
+ 0.25d0*OOVV(i,j,a,b)*t2(i,j,a,b)
end do
end do
end do
end do
end subroutine CCSD_Ec_nc