Elastic and optoelectronic properties of CaTa2O6 compounds: Cubic and orthorhombic phases

Using first principles density functional theory (DFT) simulations, the structural, electronic, optical and elastic properties of CaTa₂O₆ oxide for cubic and orthorhombic phases are studied by highly accurate (FP-LAPW) method within the GGA + U approximation. The calculated lattice parameters are consistent with available experimental data. The electronic band structure calculations have shown that the band gaps in CaTa₂O₆ are equal to 3.08 eV and 4.40 eV for the cubic and orthorhombic structures, respectively. For both the phases the main optical properties, e.g., absorption coefficient, dielectric constant, energy loss function, reflectivity are calculated and discussed in detail in the spectral range 0–14 eV. Cubic and orthorhombic phases exhibit significantly different optical characteristics. The electronic bonding characters of CaTa₂O₆ with different symmetries are explored via charge density distribution mapping. Strong covalent bonding character dominates in both the phases of CaTa₂O₆. Elastic properties of CaTa₂O₆ for cubic and orthorhombic phases are also investigated. The stress strain method is used for the determination of elastic constants in both the phases. The bulk modulus, shear modulus, Young's modulus, along with the important elastic anisotropy factors and Poisson's ratio are studied in detail.