Determining the site preference of trivalent dopants in bixbyite sesquioxides by atomic-scale simulations

Oxides with the bixbyite structure (Ia(3) over bar) have two crystallographically unique cation sites, namely (in Wyckoff notation) 24d and 8b. Since the symmetries of these two sites are different (C-2 and S-6, respectively), properties related to solute cations will vary depending on the site preference. Therefore, we have employed atomic scale simulation techniques to systematically investigate the solution site preference of a range of trivalent cations ranging from Sc3+ to La3+ in A(2)O(3) bixbyite oxides (where A ranges from Sc to La). Results reveal that when the solute cation is smaller than the host lattice cation, the 24d site is energetically favorable, but when the solute cation is larger than the host lattice cation, the 8b site is preferred. We also discuss the tendency for solute cations to cluster, as well as corroboration of this work by first principles methods.