Abstract
Explicit inclusion of electron correlation into the MNDO model leads to the semiempirical MNDOC method which
is parametrized for the elements H, C, N, and 0. Correlation is treated in MNDOC by second-order Brillouin-Wigner perturbation
theory with Epstein-Nesbet energy denominators, although it is shown that configuration interaction approaches can also be applied with the use of unmodified MNDOC parameters. Calculated heats of formation and geometries for closed-shell ground
states are of similar accuracy in MNDOC and MNDO which is rationalized by an analysis of the MNDOC correlation effects
in these systems.
