A First‐Principles Study of Structural, Elastic, Mechanical, Thermodynamic, and Electronic Properties of Rb2XIO6 (X = Ga, In) Double Perovskites

Double perovskites (DPs) have gained the interest of researchers due to their unique properties. In present work, structural, mechanical, electronic, and thermodynamic properties of Rb 2 XIO 6 (X = Ga, In) DPs are investigated using first‐principles calculations. The tolerance and octahedral factors are calculated in the allowed range of DPs. The phonons dispersion curves were computed with positive frequencies. The elastic constants prove the mechanical stability. Mechanical properties explore the anisotropic, brittle, and stiffer nature of both DPs. The computed band structures discover the metallic nature, where O– p and I– s states are found to cross the Fermi level. Debye temperature for Rb 2 GaIO 6 is calculated higher than Rb 2 InIO 6 . Grüneisen parameter is evaluated to decrease with increasing pressure and temperature. Specific heat capacity is observed to saturate at 450 K. The coefficient of thermal expansion are calculated as 9 10 −5 and 8.95 10 −5 K −1 at 1000 K for Rb 2 GaIO 6 and Rb 2 InIO 6 , respectively.