Intrinsic polarization mechanism of CCTO based on optimized Skanavi model with displacement fields modification

Abstract

To elucidate the microscopic origin of the giant dielectric properties in perovskite calcium copper titanate (CCTO), this study proposes a novel optimization of the Skanavi model by incorporating ionic polarization displacement fields. The optical dielectric constant is calculated using the Shannon ionic radius, which accounts for coordination number and electron spin state effects, while the static dielectric response is analyzed through the introduced displacement field. By evaluating the effective electric field ratios of Ca2+, Cu2+, Ti4+, and O2- ions under varying supercell sizes (1×1×1 to 19×19×19), we observe that Ca2+ and Ti4+ exhibit robust lattice stability, whereas Cu2+ polarization direction reverses and O2- polarization amplitude diminishes significantly. The computed optical (ε∞≈6.8) and static (εs≈77) dielectric constants align closely with sub-infrared room-temperature experimental values (ε∞=6.5, εs=70), demonstrating the model’s accuracy. Notably, in the 19×19×19 supercell, Ca2+ and TiO6 octahedra dominate the static dielectric response (contributing +61.28 and +30.81, respectively), while CuO4 squares exhibit a negative contribution (-11.94). This work provides a theoretical framework for understanding the dielectric behavior of CCTO and other high - dielectric - constant dielectrics, and offers guidance for the design of high - performance electronic materials.