Transition-metal-based halide double perovskites constitute a new fascinating playground for investigating the deep relationship between the crystal structure, unique physical properties and their promising applications. Among these halides, Rb2MCl6 are attractive compounds since they show ferromagnetic, half-metallic (HM) and semiconductor natures due to the M-site substitution effect. In this work, we have studied the structural, thermodynamic, magnetic and electronic properties of perovskites Rb2MCl6 (M = V, Cr, Mn). Theoretically, the current investigations have relied heavily on Wien2k computational code, which exploits the density functional theory (DFT) based on generalized gradient approximation (GGA). Herein, we analyzed the effect of M-3d on the core physical properties of Rb2MCl6. We found that all Rb2MCl6 compounds are stable and crystallize in the face-centered cubic (fcc; Fm-3 m) structure. The electronic band structures and density of states indicate that Rb2MCl6 compounds exhibit HM nature for (M = V and Cr), and semiconductor behavior for (M = Mn). The direct band-gap for HM cases is found to be in the spin-down with 2.128 eV (M = V) and 2.111 eV (M = Cr), whereas (M = Mn)-based semiconductor compound shows a band-gap of 1.264 eV in spin-up and 1.701 eV in spin-down. The magnetic properties confirm that perovskites Rb2MCl6 are ferromagnetic (FM) materials with an integer total magnetic moment of 1.0 µB, 2.0 µB and 3.0 µB, respectively, in good agreement with the expected high-spin state of unpaired electrons on the M-3d ions. The above results reveal that the Rb2MCl6 perovskites are reliable inorganic materials and candidates for spintronics and optoelectronics applications.
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