Résumé:
In this work, we studied the structural, elastic, and thermodynamic properties of the compounds Li_2TiBr_6 and Na_2TiBr_6 using Density Functional Theory (DFT). The calculations were performed using the Generalized Gradient Approximation (GGA) according to the Perdew-Burke-Ernzerhof (PBE) approach, as implemented in the Quantum ESPRESSO code. The elastic constants C11, C12 and C44, bulk modulus B, Shear modulus G, Young’s modulus E, and Poisson’s ratio ν were determined. The obtained results satisfy the mechanical stability criteria for cubic structures, indicating the mechanical stability of these compounds. Finally, we investigated the thermodynamic properties of the A_2TiBr_6 compounds (A = Li, Na), such as the thermal expansion coefficient and the heat capacity at constant volume C_V, in a temperature range from 0 to 800 K. The obtained results were analyzed and discussed. Keywords: DFT, GGA-PBE, Quantum ESPRESSO, electronic, elastic, and thermodynamic properties
