Strontium migration assisted by oxygen vacancies in SrTiO₃ from classical and quantum mechanical simulations

We present the pathways for strontium ion migration in SrTiO₃, which are based on an exploration of the potential energy landscape through a combination of classical and quantum mechanical techniques. Sr ion migration is enhanced by interaction with an anion vacancy: In the bulk material, Sr cations migrate linearly between adjacent lattice sites, through the center of a square formed by four oxygen ions; however, the activation barrier is substantially reduced, and the path curved, in the presence of an oxygen vacancy. The contribution of partial Schottky disorder in the SrO sublattice to ion migration explains the wide spread of experimental results to date, with direct implications for diffusion processes at highly doped surfaces and interfaces of SrTiO₃ as well as other perovskite materials.