FRAGMENT FORMALISM IN MAIN-GROUP SOLIDS - APPLICATIONS TO ALB2, CAAL2SI2, BAAL4, AND RELATED MATERIALS

Some aspects of the structures of the anion nets in the CaAl2Si2 and BaAl4 structure types are investigated by using the techniques of tight-binding theory. We examine the factors that stabilize main-group compounds that adopt AlB2, CaIn2, and CaAl2Si2 structure types for similar electron counts, i.e., the half-filled band. Traditional molecular orbital concepts and the method of moments are combined to compare the two structural isomers CaAl2Si2 and BaAl4. Furthermore, we utilize two-dimensional pieces of these two structures as fundamental building blocks to form other main-group compounds. © 1990, American Chemical Society. All rights reserved.