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The generalized hybrid orbital (GHO) method provides a way to combine quantum mechanical (QM) and molecular mechanical (MM) calculations on a single molecular system or supramolecular assembly. The GHO method is extended to the ab initio Hartree-Fock (HF) level (GHO-AIHF).

Ab initio individual gauge for localized molecular orbital (IGLO) techniques of SCF-MO theory are used to study the mathematical form of the conformational dependencies of the isotropic 13C chemical shifts of cyclobutale and nitrile, methyl and fluoro derivatives. It was observed that calculated 13C chemical shifts equilibrium geometries compared favorably with the experimental data. Conformational and substituent effects are studied in terms of the angular dependence of the 1GLO C-H and C-C bond paramagnetic contributions significant for equatorial C-H or C-X bonds.

Molecular orbital studies, using the all-valence electron SCF SINDO1 method, evaluate the aromaticity of the phosphorus analogues of the cyclopentadienyl anion. Optimized geometries place the ring bond lengths between those of single and double bonds, thus suggesting their aromatic character. The 1,3-diphospha isomer shows higher aromaticity than the 1,2-diphospha form. Of the triphospha analogues, the 1,2,4-isomer is more aromatic than the 1,2,3-isomer. The study discovers the tendency to form complexes as a strong marker of aromaticity.

The mechanisms and kinetics of the reaction of a thiocyanato radical (NCS) with NO are examined by a high-level ab initio molecular orbital method in conjunction with variational RRKM calculations. The results have shown favorable pathways for the formation of many isomers of an NCSNO complex.