Computer simulation study of the defect chemistry of rutile TiO2

We examine the defect chemistry of rutile TiO2 using computer simulation techniques. The stable valencies of dopant transition metal ions in TiO2 are calculated to be Nb(V), V(III), Fe(III) and Cr(III). We find that Cr3+, Al3+, Ga3+, V3+ and Fe3+ dissolve preferentially at substitutional sites in TiO2 with charge compensation by oxygen vacancies rather than Ti4+ interstitials, although experimentally both are observed. Nb5+ is calculated to dissolve preferentially at substitutional sites with charge compensation being facilitated via Ti(III) ions or titanium vacancies. The solution enthalpy of Nb5+ is reduced by the introduction of Al3+ into the lattice. The solution enthalpy is further reduced when we consider bound Al3+ Nb5+ clusters. © 1995.