Electronic Structures of Antimony Oxides

This study details density functional theory calculations on all the polymorphs of the binary oxides of antimony (Sb2O3, Sb2O4, and Sb2O5) to assess the electronic structures and differences in bonding between Sb-III and Sb-V ions with oxygen. The results show that lone-pair formation is via a similar mechanism to other main group elements which exhibit an oxidation state of two less than the group valence, through direct interaction of Sb 5s and O 2p states, with the antibonding interaction stabilized by Sb 5p states. Furthermore, structural distortion of the Sb site directly affects the strength of the resulting lone pair. In addition to the analysis of the density of states and charge density, band structures and optical absorption spectra are also detailed. The results indicate that all materials are indirect band gap materials, with the exception of the beta-polymorphs of Sb2O3 and Sb2O4. In addition, the fundamental and optical band gaps of the materials are found to decrease from Sb2O3 to Sb2O4 to Sb2O5. Calculated band-edge effective masses suggest that beta-Sb2O3 may exhibit reasonable p-type properties. Furthermore, beta-Sb2O3, gamma-Sb2O3, and Sb2O5 possess low electron effective masses which are conducive with strong n-type conduction.