SEMI-EMPIRICAL MOLECULAR-ORBITAL CALCULATION OF ATOM-PAIR INTERACTIONS IN A MOLECULE

A simple procedure is proposed to resolve the binding energy calculated from a semiempirical MO method into terms that are representative only of atom-pair interactions. These interactions are comparable to traditional bonded and nonbonded interactions. Practical calculations for a homologous series of compounds require parameter values to be determined for the series. The parameter values may be evaluated unambiguously from key compounds. Examples for the evaluation of parameter values are given for saturated hydrocarbons, amines, alcohols, and ethers using energy quantities obtained from a modified CNDO method. Preliminary calculations are made for benzene, ethylene, and acetylene. Applications of the proposed energy partitioning technique yield quantum chemical estimates of “bond energies” that are comparable in magnitude to those discussed traditionally. © 1979, American Chemical Society. All rights reserved.