Hartree-Fock perturbed-cluster treatment of local defects in crystals III. The use of local symmetry

✍ Scribed by C. Pisani; F. Corà

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 800 KB
• Volume: 82
• Category: Article
• ISSN: 0010-4655
• DOI: 10.1016/0010-4655(94)90165-1

✦ Synopsis

This paper is the third of a series to illustrate the characteristics of EMBED, a computer program for the ab-initio Hartree-Fock study of defects in crystals. We describe here the algorithms which allow the symmetry of the imperfect crystal to be identified, and exploited thoroughly. Much of the discussion concerns the generation of orthogonalized symmetry orbitals (OSO) in the cluster subspace: they are classified according to the different rows of the different irreducible representations (IRREP's) of the point group of the system. Using the OSO basis set inside the cluster, and the usual atomic orbital basis set in the surrounding crystal permits us to factorize completely the problem by the different IRREP's with important savings in computer time and storage requirements. This benefit is demonstrated by considering the example of a lithium impurity in bulk MgO, with lithium at the center of a cubic interstice or slightly off-center.