Matrix elements for an approximate ab initio π-electron theory

✍ Scribed by Phillip W. Pilkington; Stanley C. Neely

• Book ID: 104578846
• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 935 KB
• Volume: 10
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/qua.560100310

✦ Synopsis

Abstract

This work involves the derivation of approximate forms for the matrix elements of an ab initio π‐electron molecular orbital theory. The result may be described as a complete neglect of differential overlap mathematical formalism plus σ‐π exchange. The basis set of π atomic functions for these derivations is a set of approximate Löwdin orthogonalized atomic orbitals (LOAO's) produced by successive pairwise orthogonalization. Using these functions, we derive approximate equations for the one‐electron integrals of molecular orbital theory, α and β, which, for the first time, show the effects of overlap‐coupling in a molecule. Many new methods of approximation enter the theory. There are approximate equations for π‐electron, nuclear attraction potentials and for π‐electron, σ‐core repulsion potentials, all approximations are compared to more accurate calculations where possible. A mechanism is also included for testing the effects of σ‐charge shifts upon the results of the π‐electron calculations.