Explorations of stable lead-free perovskites have currently achieved substantial interest to overcome the instability and avoid toxicity related issue faced with the lead-based perovskites. In this study, we have comprehensively studied the stability, nature and origin of electronic, transport and optical properties of inorganic halide double perovskites, which could provide a better understanding of their possible potential applications. The density functional theory is used to investigate the different physical properties of these materials. The stability of these cubic materials is validated by optimizing the structure, tolerance factor, mechanical stability test. The materials are small band gap semiconductors with outshining optoelectronic performance. Due to high optical absorption, high conductivity and low reflectivity they have great potential to be used for optoelectronic application purpose. Because of small band gap we have also investigated the variation of various transport parameters with chemical potential. The semiconducting nature of materials results in ZT close to unity predicting its excellent application in thermoelectric technology.

The structural, electronic, optical, thermodynamic and thermoelectric properties of double perovskites Ba2MTaO6 (M = Er, Tm) have been studied.

Summary The state‐of‐the‐art density functional theory is used to investigate various properties of rare‐ earth based inverse perovskites Gd3AlX (X = B, N). The materials show robust structural stability at high pressures without undergoing any phase transition. The ferromagnetic character is retained at high pressures with high value magnetic moments 7.09 μB and 7.38 μB at 0 GPa for Gd3AlB and Gd3AlN, respectively. In view of Poisson's and Pugh's ratio, the ductility and brittleness of Gd3AlX (X = B, N) has been analyzed. The mechanical stability is maintained throughout the pressure range with high value of Debye temperature. Transport properties have been calculated at different pressures for both the alloys, which show excellent thermoelectric properties. Besides, this the variation on some significant thermodynamic properties is also studied. Our successful prediction of the stabilization of the metallic Gd3AlX (X = B, N) has proposed a route to synthesize novel rare‐earth–based inverse perovskites.

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Summary The tantalum‐based double perovskites Ba2MTaO6 (M = Mn, Cr) are studied to understand the effect of pressure on structural, electronic, magnetic, thermodynamic, and thermoelectric properties by means of density functional theory. Ba2MTaO6(M = Mn, Cr) perovskites' own maximum stability in ferromagnetic phase with calculated high magnetic moments of 4.02 and 3.0 μB at zero pressure. Ba2MTaO6 (M = Mn, Cr) perovskites display complete spin polarization, ensuing the half metallic behavior. Effect of high pressure on the electronic structure and magnetism was also studied. The compounds have wide band gap that varies from 2.63 to 2.56 eV as the pressure increases from 0 to 25 GPa in Ba2CrTaO6, while as in Ba2MnTaO6 band gap varies from 2.24 to 1.95 eV as the pressure increase from 0 to 25 GPa. The magnetic moment also shows a decreasing inclination with increase in pressure in both compounds. Also, we calculated the heat capacities, thermal expansion coefficients, Debye temperature and Grüneisen parameter by using the Debye model. Boltzmann's theory was employed to perform post DFT treatment to investigate the thermoelectric properties of the compounds.