  The energy and analytic gradient are developed for FMO combined with the
Hartree-Fock method augmented with three empirical corrections (HF-3c). The
auxiliary basis set approach to FMO is extended to perform pair interaction
energy decomposition analysis. The FMO accuracy is evaluated for several
typical systems including 3 proteins. Pair interaction energies computed with
different approaches in FMO are compared for a water cluster and protein-ligand
complexes.
