The density functional theory (DFT) is applied to systematically investigate the geometrical structure, electronic, mechanical, vibrational, and optical properties of double perovskite Rb₂LiTlF₆ in its cubic phase. To the best of one's knowledge, many physical properties of this compound are still not well established or not yet investigated; such as phonon properties, mechanical behavior, thermal properties, and so on. In this work, the stability of Rb₂LiTlF₆ is explored by looking at its thermodynamical behavior through calculation of formation energy, cohesive energy, Goldschmidt tolerance factor, and phonon dispersion. Its mechanical properties are examined based on various characterization descriptors such as the independent elastic coefficients, bulk, shear, and Young's modulus, ratios such as Pugh and Poisson's, Kleinnman parameter, Zener anisotropy factor, Debye temperature, and melting temperature. Sound velocity in this material is predicted from the values of the bulk and shear modulus obtained. Thermal expansion coefficient at finite temperatures are obtained using the approach of quasi‐harmonic approximation. Its electronic property is also investigated using generalized gradient approximation and also hybrid functionals. At a later stage, its optical behavior upon the effect of light excitation is explored using the many body pertubation theory approximation. Having envisioned this material as a wide band gap semiconductor, it can be useful in numerous applications such as designing the top‐cell of tandem photovoltaic configuration, photodetection, and light emitting diodes. It is strongly believed that this work will provide a helpful guidance for future experimental and theoretical investigations of this material.

The structural, electronic, mechanical, and optical properties of pseudo-cubic CH₃NH₃PbI₃ perovskite have been studied within the framework of density functional theory, in line with solar cell applications. The computed values of lattice and elastic constants concurred with the available theoretical and experimental data. This compound has a semi-conducting behavior, with a direct band gap of about 1.49 eV. Note that the solar radiation spectrum has a maximum energy intensity value of approximately 1.50 eV. Thus, semiconductors with such gaps are preferred for photovoltaic applications. Its elastic parameters reveal that it is a ductile material that is mechanically stable. Optical descriptors such as refractive index, reflectivity, extinction, energy loss, and absorption have been explored with the aim of establishing the optical features of the material. Our findings demonstrate that this perovskite is suitable for solar cell applications based on the size and nature of the band gap, as also supported by the obtained upper limit value of simulated power conversion efficiency via the spectroscopic limited maximum efficiency mathematical model.

Structural properties of $$\hbox {CdGa}_{2}\hbox {Se}_{4}$$ CdGa 2 Se 4 and $$\hbox {ZnGa}_{2}\hbox {Se}_{4}$$ ZnGa 2 Se 4 ternary compounds in their tetragonal phase have been investigated using the first-principles approach. These materials are stable, as supported by the computed vibrational and mechanical properties. Having established their stability, prediction of their thermal conductivity and consequently the dimensionless figure of merit was undertaken. According to the simulations results, these ternary compounds have fairly low values of lattice thermal conductivity of about 1.45 and 1.25 W/mK at room temperature for $$\hbox {CdGa}_{2}\hbox {Se}_{4}$$ CdGa 2 Se 4 and $$\hbox {ZnGa}_{2}\hbox {Se}_{4}$$ ZnGa 2 Se 4 , respectively. Their Seebeck coefficient and electrical conductivity are moderate, resulting in outstanding thermoelectric properties as backed by the dimensionless figure of merits that are beyond unity, i.e., 1.17 and 1.27 for $$\hbox {CdGa}_{2}\hbox {Se}_{4}$$ CdGa 2 Se 4 and $$\hbox {ZnGa}_{2}\hbox {Se}_{4}$$ ZnGa 2 Se 4 , correspondingly at a temperature of 1000 K. To our understanding, until now, there is lack of scientific report about thermoelectric properties of these compounds, forming the novelty of this study. Graphic