Research on the influence of uniaxial stress on the properties of PbTiO3 using first-principles

Abstract

As a classic type of ABO₃ ferroelectric ceramic, PbTiO${}_3$ is widely applied in fields such as electronic communication and piezoelectric driving. However, the influences of uniaxial stress on its structure, elasticity, and optical properties remain unclear. This study adopted the first-principles method based on density functional theory to investigate the changes in properties like the crystal structure and electronic structure of PbTiO${}_3$ under the action of uniaxial tensile and compressive stresses. Based on the time-dependent density functional theory (TD-DFT), the optical properties including the dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss coefficient were calculated. It was found that when the uniaxial compressive stress was approximately 3.7 GPa, the structure transformed from the tetragonal phase to the cubic phase. When the compressive stress reached 4 GPa, it became a direct bandgap semiconductor. The uniaxial tensile stress increased the bandgap value by a maximum of 11.6 %, yet it always remained an indirect bandgap semiconductor. The mechanical properties of PbTiO${}_3$ gradually increased with the increase of uniaxial compressive stress, while the uniaxial tensile stress increased its degree of anisotropy. Regarding optical properties, the uniaxial compressive stress increased the static dielectric function and static refractive index, and the uniaxial tensile stress increased the extinction coefficient and electrical conductivity. However, it had a relatively small impact on the energy loss coefficient. This study provides theoretical guidance for understanding the response mechanism of PbTiO${}_3$ to stress-induced modulation and for the research and development of high-performance and stable piezoelectric devices.