The Ab-Initio Investigation of Structural, Electronic, Mechanical, Dynamical and Thermodynamic Properties of Double Halide Cs2SrTaCl6, Cs2SrTaBr6, and Cs2BaTaBr6 Perovskites: A Dispersion Corrected DFT Study

초록

Ab-initio density functional theory (DFT) study of double halide Cs2SrTaCl6, Cs2SrTaBr6, and Cs2BaTaBr6 perovskites has been performed. The structural, electronic, phonon dispersion curves, thermodynamic and mechanical properties have been calculated for these materials. The computed values of cohesive energy are - 5.23 eV/atom for Cs2SrTaCl6, - 4.37 eV/atom for Cs2SrTaBr6, - 6.41 eV/atom for Cs2BaTaBr6, respectively. The observed negative values of cohesive energy result in completely relaxed, optimized, compactable, and stable structure. The electronic properties show the metallic behavior of all the given halides. The phonon dispersion curves show that only positive phonon's modes exist for Cs2SrTaCl6, Cs2SrTaBr6, and Cs2BaTaBr6. The free energy has been observed to be - 6.31 eV for Cs2BaTaBr6, - 5.98 eV for Cs2SrTaBr6, and - 5.40 eV for Cs2SrTaCl6, respectively. The negative free energy verifies the thermodynamic stability of all these halides. The maximum bulk modulus has been found to be 72.375 GPa for Cs2BaTaBr6. The critical value of Poisson's coefficient has been found to be 0.26 for all the given double halide perovskites, showing their ductile nature. All these DFT based calculations strongly recommend that these materials are favorable for photovoltaic devices and related applications.

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