Structures and elastic properties of paraelectric and ferroelectric KTa 0.5Nb 0.5O 3 from first-principles calculation

Abstract

The structures, elastic properties and intrinsic hardness of B–O bonds of KTa 0.5Nb 0.5O 3 crystal in paraelectric and ferroelectric phase structures have been investigated by means of the density functional theory. Both structures are found to be elastically stable and in good agreement with available results. The elastic properties including the bulk modulus, shear modulus and Young’s modulus change largely during phase transition. The paraelectric KTa 0.5Nb 0.5O 3 crystal is more incompressible and harder than ferroelectric phase. The hardness of KTa 0.5Nb 0.5O 3 crystal is mostly determined by Nb–O bonds and the modifications of the bond strength affect the hardness of the crystal. Charge density contours indicate that the electronic distributions between B–O bonds play an important role in the formation of elastic properties.