Electronic structure and chemical bonding in bismuth sesquioxide polymorphs

The electronic structure of the alpha-Bi2O3, beta-Bi2O3, and gamma-Bi2O3 ph ases was investigated by the ab initio self-consistent LMTO method in a tig ht binding approximation and by the semiempirical Huckel method. The total and partial densities of states and Mulliken overlap populations were obtai ned. The stability of bismuth oxide polymorphs is discussed based on the re sults of the total energy calculations for crystals. An analysis of chemica l bonding shows that the Bi-O interaction plays the leading role. The Bi-Bi metallic bond is absent. Mechanisms of oxygen ion migration and possible s tabilization of the structure of the superionic conductor delta-Bi2O3 are d iscussed.