Tunability of half metallicity and thermoelectric indicators in Na2TaX6 (X = Cl, Br) vacancy ordered double perovskites

[Display omitted] •Formation energy calculation and Born stability criteria confirm their thermodynamic and mechanical stability.•The study of intrinsic magnetic moments unveils their potential for spintronic devices.•Thermoelectric properties highlight their ability to efficiently convert heat into electricity. With the growing development in spintronics and thermoelectrics, researchers across the globe are extensively trying to fabricate and characterize novel materials. In this regard, the current work analyses the magnetic and thermoelectric characteristics of vacancy-ordered double perovskites Na2TaX6 (X = Cl, Br) computed using density functional theory. The geometry optimization reveals a cubic crystal structure with a relatively more stable ferromagnetic state. The mechanical and thermodynamic stability analyses also indicate the stability of both compounds. The computed electronic band structures demonstrate a half-metallic (HM) nature with metallic behavior in the up-spin channel. A semiconducting nature in down-spin configuration shows a direct bandgap of 3.6 eV and 4 eV for Na2TaCl6 and Na2TaBr6, respectively. The computation of transport parameters is found suitable for thermoelectric device applications. The present study demonstrates the high potential of the examined materials for applications in energy conversion and spintronics devices.