Srbo <sub> 3 </ Sub> (b = Zr, Hf) Polarization Of The Surface Structure And Stability Theory

The cubic SrZrO3 and SrHfO3 surfaces were systematically investigated by means of the density functional theory (DFT) plane-wave pseudopotentials method using a periodic slab model. We used the CASTEP computational code to perform relevant calculations for the atomic structures, electronic structures, and thermodynamic stability of the bulk crystal as well as five (110) polar surfaces. And furthermore, we explored the relationships between structures and properties of materials.The detailed calculation results for the bulk electronic structure of the cubic SrZrO3 and SrHfO3 showed that the two stoichiometric terminations of the (110) polar surface undergo significant changes with respect to bulk materials. On the SrBO termination, an anomalous filling of conduction band was observed, and this surface possessed metallic characteristic. On O2 termination, two surface oxygen atoms close to each other and form a peroxo group. However, for the three nonstoichiometric BO-, Sr-and O-terminated surfaces, their electronic structures are very similar to the bulk crystal, and kept insulating property. Charge redistribution results for the five terminations confirmed that electronic structure and surface composition changes are responsible for their polarity compensation. A thermodynamic stability diagram suggested that SrBO stoichiometric terminations were unstable; however, O termination and the three nonstoichiometric terminations can be stabilized in some given regions. The differences among the two studied materials and SrTiO3 and BaTiO3 come from the intense antiferroelectric distortion of bulk SrZrO3 and SrHfO3.