Just how ab initio is ab initio quantum chemistry?

Abstract

Quantum Mechanics has been the most spectacularly successful theory in the history of science. As is often mentioned the accuracy to which the gyromagnetic ratio of the electron can be calculated is a staggering nine decimal places. Quantum Mechanics has revolutionized the study of radiation and matter since its inception just overonehundredyears ago. Theimpactof thetheoryhas been felt in such fields as solid state physics, biochemistry, astrophysics, materials science and electronic engineering, not to mention chemistry, the subject of this conference. Quantum Mechanics offers the most comprehensive and most successful explanation of many chemical phenomena such as the nature of valency and bonding as well as chemical reactivity. It has also provided a fundamental explanation of the periodic system of the elements that summarizes a vast amount of empirical chemical knowledge. Quantum Mechanics has become increasingly important in the education of chemistry students. The general principles provided by the theory mean that students can now spend less time memorizing chemical facts and more time in actually thinking about chemistry. I hope that with these opening words I have succeeded in convincingtheaudiencethat Ido notcomebefore youto denythepower and influence of Quantum Mechanics in the field of chemistry. � A previous version of this article appeared as ‘Lowdin’s Remarks on the Aufbau Principle and a Philosopher’s View of Ab Initio Quantum Chemistry’ in E.J. Brandas, E.S. Kryachko (Eds.) Fundamental World of Quantum Chemistry, Vol. II, 675‐694, Kluwer, Dordrecht, 2003.