Elastic constants and their variation by pressure in the cubic PbTiO3 compound using IRelast computational package within the density functional theory

Abstract

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; text-align: justify; font: 12.0px 'Times New Roman'} span.s1 {font: 12.0px 'B Nazanin'} p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; text-align: justify; font: 12.0px 'Times New Roman'} span.s1 {font: 12.0px 'B Nazanin'} In this paper, we study the structural and electronic properties of the cubic PbTiO3 compound by using the density functional theory. For the calculation of band structure and density of states, we use the modified Becke–Johnson exchange potential proposed by Tran and Blaha (TB-mBJ), including the relativistic spin-orbit coupling (SOC). The results obtained from TB-mBJ functional and SOC calculations show that the calculated band gap is 2.18 eV. IRelast computational package is very recently implemented into the WIEN2k code and can be used to calculate the elastic constants of the crystal structures, where IR stands for Iran. We calculate the elastic constants of this compound by the IRelast code using the PBE-GGA, PBEsol-GGA, LDA, BPW91 and Engel-Vosko functionals. Then, by these elastic constants, we obtain some other related physical quantities such as shear constant, bulk modulus, Young’s modulus and Poisson’s ratio. Furthermore, we calculate the ductility of the compound under question. The calculated ductility shows that our compound is formable and not fragile. The effect of pressure on the elastic constants shows that C11, C12 and C44 are increased as the pressure is raised inside the considered pressure interval. Furthermore, the longitudinal and transverse sound velocities are derived for the compound using its calculated elastic constants. The results, therefore, show that the sound velocities, like elastic constants, are increased as pressure is raised .

Keywords

• density functional theory
• band structure
• density of states
• elastic constants
• sound velocities