Transferable variable-charge interatomic potential for atomistic simulation of titanium oxides

A transferable interatomic potential for atomistic simulation of titanium oxides was obtained by parametrizing a Morse--variable-charge model with crystal structures of rutile, anatase, brookite, TiO₂-II, Ti₂O₃, and monoclinic high- and low-temperature Ti₃O₅ forms, and elastic constants of rutile. The transferability of the potential was assessed through lattice energy minimisation of the structures included in the fitting as well as some selected structures representing various Ti-O stoichiometries and oxidation states of Ti. In addition, the transferability of the bulk-derived potential to surface simulation was tested by evaluating relaxation characteristics of the (100) rutile surface. The results suggest that for simulating crystal structures the model is applicable across different stoichiometries, polymorphs, and Ti oxidation states. The model also is successful in predicting the bulk moduli of various phases, the relative stability of the TiO₂ polymorphs, and the relaxation of (100) rutile surface.