ELECTRONIC-STRUCTURE OF SNO2, GEO2, PBO2, TEO2 AND MGF2

The band structures and densities of states for a number of non-transition-metal compounds with the rutile structure are calculated using a tight-binding method with scaled two-centre interactions. For SnO2, the valence band maximum state is calculated to have Gamma 3 + symmetry in agreement with experimental results, and the calculated valence-band density of states is in fair agreement with photoemission. The simplicity of the LCAO approach is utilised to give algebraic expressions for the energy and nature of each band and used to discuss bonding and ionicity. The importance of the long-pair oxygen orbitals in forming the upper valence bands of SnO2 is stressed. TeO2 is discussed as an example of a class of compounds in which the two cation s electrons remain bound, giving rise to a cationic gap. The calculated joint density of states can be used to account for the experimentally observed optical dispersion.