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In this study, we carried out ab-initio calculations of structural, electronic, optical and thermo-electric properties of CaTaO2N compound in Pnma orthorhombic structure, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). The calculated structural parameters are found to be in good agreement with the experimental results. Moreover, we have studied the electronic band structure, total and partial density of states in order to explain the origin of band gaps and the nitrogen anion contribution in the valence and the conduction bands. The CaTaO2N band structure has shown a direct band gap in the direction [Formula: see text] (with the value 2.32[Formula: see text]eV). The optical properties represented by the dielectric functions for CaTaO2N compound have revealed that the Pnma structure absorbs the light at a large window in the edge UV-Vis regions. In order to explain the thermo-electric properties, we have calculated Seebeck coefficient, electrical conductivity, thermal conductivity and the factor figure of merit in this temperature range 100–1000 K. The factor figure of mérit (ZT) of CaTaO2N takes a maximum value of 0.775 at [Formula: see text][Formula: see text]K.

This report presents a first-principles investigation of the structural, electronic, and optical properties of perovskite oxynitrides BaTaO 2 N by means of density functional theory (DFT) calculations using the full-potential linearized augmented plane wave (FP-LAPW) method. Three possible structures (P4mm, I4/mmm, and Pmma) are considered according to the TaO 4 N 2 octahedral configurations. The calculated structural parameters are found to be in good agreement with the previous theoretical and experimental results. Moreover, the electronic band structure dispersion, total, and partial densities of electron states are investigated to explain the origin of bandgaps and the contribution of each orbital's species in the valence and the conduction bands. The calculated minimum bandgaps of the P4mm, I4/mmm, and Pmma structures are 1.83 eV, 1.59 eV, and 1.49 eV, respectively. Furthermore, the optical properties represented by the dielectric functions calculated for BaTaO 2 N show that the I4/mmm phase absorbs the light at a large window in both the visible and UV regions, whereas the other two structures (P4mm and Pmma) are more active in the UV region. Our investigations provide important information for the potential application of this material.

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