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

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 O^2- 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 O^2- polarization amplitude diminishes significantly. The computed optical (ε_∞ ≈ 6.8) and static (ε_s ≈ 77) dielectric constants align closely with sub-infrared room-temperature experimental values (ε_∞ = 6.5, ε_s = 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.