HElement_t(dp) function GetH0Element4(nI, HFDet)
! Returns the matrix element of the unperturbed Hamiltonian,
! which is just the sum of the eigenvalues of the occupied
! orbitals and the core energy.
! HOWEVER, this routine is *SLOWER* than the GetH0Element3
! routine, and should only be used if you require this
! without reference to the fock eigenvalues.
! This is calculated by subtracting the required two electron terms
! from the diagonal matrix elements.
integer, intent(in) :: nI(NEl), HFDet(NEl)
HElement_t(dp) :: hel
hel = SumFock(nI, HFDet)
GetH0Element4 = hel + ECore
end function GetH0Element4