correlation energy

The difference between the Hartree–Fock energy calculated for a system and the exact non-relativistic energy of that
system. The correlation energy arises from the approximate representation of the electron-electron
repulsions in the Hartree–Fock method.

Source:

PAC, 1996, *68*, 2223*
(Glossary of terms used in photochemistry (IUPAC Recommendations 1996))
* on page 2234