Energy partitioning with the CNDO method

Abstract

The partitioning of the total energy from CNDO computations into mono and bicentric terms and into physical components is examined. It is noted that the two-center terms are a measure of the strength of the chemical bond. This relationship is illustrated in the case of a nonclassical bond in a carbonium ion. The consideration of the interaction between vicinal H atoms leads to the discovery of a trans effect which is important in the interpretation of torsional barriers in hydrocarbons. The investigation of the structure of C-C bonds and the analysis of the derivatives of the total energy with respect to a bond length gives hints which are important for the parametrization of a semiempirical theory.