A new potential model for barium titanate and its implications for rare-earth doping

We present a new set of interatomic potentials for modelling the BaTiO3 perovskite system. The potential model is fitted using multiple parameters to a range of experimental and ab initio data including the cohesive energy and lattice parameters of BaTiO3, BaO and rutile TiO2. This procedure provides internal consistency to the potential model for studying the energetics of the defect chemistry of BaTiO3. This is tested by examining rare-earth cation doping in BaTiO3 and considering all five possible compensation schemes. Our simulations are in agreement with experiment and predict small rare-earth cations to dope exclusively on the Ti site; medium sized rare-earth cations to dope on both the Ti and Ba sites and large rare-earth cation doping exclusively on the Ba-site. For Ba-site substitution the simulations predict electron compensation to be energetically unfavourable compared to the formation of Ti vacancies.