An alloying theory of transition metals with p-block elements I: chemical bonding and structural features in rare earth bismuthides and arsenides

Abstract

Systems of transition metals (M) and p-block elements (X) are characterized by large heats of alloying. This can be linked to the formation of strong localized covalent bonds M —X. A coherent alloying theory for these systems is of interest because the systems give rise to some of the technologically important refractory materials such as carbides, borides and nitrides. In this series of compounds the nature of the bonding in rare earth bismuthides RBi and arsenides RAs is investigated. The formation of localized covalent bonds is associated with electron transfer from the filled p orbitals of the p-block element to the rare earth orbitals d x 2−y 2 and d z 2 . The contribution of the rare earth f orbitals is also considered.