Physical characteristics of X2NaMoBr6 (X= K, Rb): A DFT study

The full-potential linearized-augmented plane-wave (FP-LAPW) method based on density functional theory (DFT) was used to investigate the structural, elastic, electronic, optical, magnetic and thermoelectric (TE) characteristics of halide double-perovskites (HDPs) X2NaMoBr6 (X = K, Rb). Perdew, Burke and Ernzerhof generalized-gradient approximation (PBEsol-GGA) + modified Becke-Johnson (mBJ) potential were employed. Enthalpy of formation (delta H) was found to be-3.243 eV for K2NaMoBr6 and-3.209 for Rb2NaMoBr6 which (negative values) confirm the stability of the compounds. The ferromagnetic behaviour was identified from the integer values of the total magnetic-moment (mu B) which were 3.00001 and 3.00002 for K2NaMoBr6 and Rb2NaMoBr6, respectively. Moreover, the value of static dielectric constant epsilon 1(0) was found to be 3.21 for K2NaMoBr6 and 3.27 for Rb2NaMoBr6. TE characteristics were calculated by using Boltztrap code. Both compounds showed the absorption in the UV region (6.86 eV for Rb2NaMoBr6 and 7.11 eV for K2NaMoBr6). Results indicate that both X2NaMoBr6 (X = K, Rb) compounds are appropriate candidates for TE, optical and data storage applications.