First-principles study on the structure instability and electronic structure of cubic Ba0.5Sr0.5TiO3

We present first-principles calculations on the structure instability and the electronic structure properties of cubic Ba0.5Sr0.5TiO3 (BST). The calculated total energy result shows that the Sr ions have a more important effect on the structure instability of BST system than the Ba ions. The off-center displacement of the Sr ions will lower the system energy and makes it instable. In order to understand the interaction between ions, the density of states and the charge density distribution were calculated. From the analysis of the density of states, we conclude that the hybridization between Ba p and O p is stronger than that between Sr p and O p. This is consistent with the analysis of the charge density distribution.