Chapter

Basic Theory and Techniques of the OLCAO Method

Wai-yim Ching and Paul Rulis

in Electronic Structure Methods for Complex Materials

Published in print May 2012 | ISBN: 9780199575800
Published online September 2012 | e-ISBN: 9780191740992 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199575800.003.0003
Basic Theory and Techniques of the OLCAO Method

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This chapter provides the basic theory of the OLCAO method which is derived from the traditional LCAO method. Atomic orbitals are used in the basis expansion where the radial part is expanded in terms of Gaussian-type of orbitals (GTOs). The OLCAO method was originally designed for the purpose of studying amorphous solids represented by large periodic atomic models. This is a very effective way of studying the electronic structure of disordered solids and non-crystalline materials. It was later found to be quite effective when applied to complex crystals, microstructural models, and multifarious biological systems. Over the years, the method has been systematically upgraded and refined in terms of its computational efficiency, accuracy, ease of use, its range of applicability to different elements and types of systems, and the inclusion of more rigorous theory. A wide variety of ancillary programs have been developed to make deep analysis of complex results more straightforward. Explicit calculation of momentum matrix elements, inclusion of core-hole screening and spin-polarization are among the many components of theory that have been implemented. Special advantages of the OLCAO method are succinctly summarized.

Keywords: atomic basis; potential functions; secular equation; Gaussian transformation; core orthogonalization; special advantages

Chapter.  10613 words.  Illustrated.

Subjects: Condensed Matter Physics

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