FIRST–PRINCIPLE ANALYSYS ON FINE STRUCTURE OF Pb0.5Sr0.5TiO3

The electronic structures and properties of Pb0.5Sr0.5TiO3 (PST) were calculated by the plane wave ultra–soft pseudo–potential and virtual crystal approximate (VCA) technologies based upon the density function theory (DFT) within the general gradient approximation. The changed trend of the total energy of PST solid solution was analyzed, and the equilibrium configuration of A–site cations (Pb and Sr) in the ferroelectric phase was determined. The calculated results revealed that the energy of PST appeared minimum when the off–center displacement of Ti atom was up to 0.012 nm along (001) direction. The strong hybridization between O 2p and Ti 3d and part hybridizations between O—Pb and O—Sr showed an increase in the distortion of TiO6 octahedron and a reduce in the system total energy, which led to the formation of ferroelectric domains.