| Summary: | The Density Functional Theory (DFT) was employed to calculate the mechanical, vibrational, structural, electronic, SLME, thermoelectric, optical, and thermodynamic properties of a double perovskite material, Rb2NaGaX6 (X = Br, Cl). The first principles computations were conducted using CASTEP and Quantum ESPRESSO. The substance Rb2NaGaX6 has a cubic crystal structure specified by the space-group symmetry Fm-3m. The lattice parameters of Rb2NaGaBr6 and Rb2NaGaCl6 were optimized by utilizing E-V curves, providing values of 7.357 Å and 7.365 Å, respectively. Mechanical properties were evaluated for the suitability of material for application. The exchange of charges across transition metals and halogen atoms was confirmed via population analysis. The investigation of phonon dispersion curves, with only positive frequencies efficiently demonstrates the stability of crystal Rb2NaGaX6 (X = Br, Cl). The band structure calculations revealed that the compounds Rb2NaGaBr6 and Rb2NaGaCl6 exhibited semi conducting behavior with direct band gaps of 0.96 eV and 0.88 eV, respectively. The optical properties results support the suitability of the examined materials for solar cell working properties in visible portion of the electromagnetic spectrum. SLME investigations revealed that Rb2NaGaBr6 has 29 % and Rb2NaGaCl6 has 7.8 % efficiency, respectively, signifying their advantage for more use in solar devices. The thermoelectric characteristics of Rb2NaGaX6 (X = Br, Cl) were computed by utilizing the BoltzTraP method. The impact of temperature on the thermodynamic properties of two compounds was assessed by utilizing quasi-harmonic Debye model. © 2024 Elsevier Ltd
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