Calculation of isoelectronic energy differences using perturbation theory

✍ Scribed by Stephen F. Sontum; Lloyd L. Ingraham; William H. Fink

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 463 KB
• Volume: 19
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/qua.560190116

✦ Synopsis

Abstract

Energy difference formulas for isoelectronic processes are derived using a perturbation series. The perturbed Hamiltonian is written as a function of a perturbation parameter that changes linearly from zero to one between the limits of the isoelectronic process. The perturbation series is based on a zero order wave function obtained when the perturbation parameter has a value of ½. For the description of changes of electronic energy with internuclear geometry, this zero order wave function will correspond to the solution of a Hamiltonian which contains atoms from both internuclear geometries, but with half their normal nuclear charge. Energy differences calculated with this formalism for the stretching of simple diatomic molecules hydrogen fluoride, fluorine, and carbon monoxide and the rotational barrier in ethane are compared with results from restricted Hartree–Fock and integral‐Hellmann–Feynman theorem energies.