The spinel chalcogenides Zn/CdSc$_2$Se$_4$ are evaluated by first-principle approach to compute optoelectronic and transport characteristics. The formation energy computations favour their thermodynamic stability. The direct bandgaps 1.0 and 0.80 eV are evaluated of the most versatile modified Becke and Johnson potential. The optical spectra have been analysed in terms dielectric constants. The absorption region expands from visible to ultraviolet, which is suitable for optoelectronics. The bandgap-dependent transport characteristics are addressed by classical theory of Boltzmann using BoltzTraP code, and a high figure of merit was noted. Finally, electron density measures the polar covalent bond in Sc-Se and Zn/Cd-Se.

With widespread physical properties from electrical to catalytic and optical to magnetic, etc., pyrochlore materials have attracted a lot more attention in the application field. In this study, we report the interatomic interactions, frequencies of Raman, and infrared phonon modes at the zone centre of mixed pyrochlore-structured compounds A$_2$GaSbO$_7$ (Y, Dy and Gd). The mechanical and elastic properties of these compounds are also reported. The obtained results show that the interatomic interaction between the atoms A–O is the strongest one as compared to the other interatomic interactions. Born’s stability conditions are found to be satisfied for all the examined compounds, showing their mechanical stability. Further analysis shows the ductile and anisotropic nature of the elastic properties for title compounds. The 3D picture of the elastic properties, such as Young’s modulus, shear modulus, linear compressibility and the Poisson ratio, is also presented and analysed. Furthermore, the obtained results are compared with previously reported theoretical and experimental results, which are found to be in good agreement where available.