DFT analysis of the structural, electronic, magnetic and thermoelectric properties of X ₂ NbI ₆ (X = Ga, In) vacancy-ordered double perovskites

First-principles calculations based on density functional theory and classical Boltzmann theory were used to study the structural, electronic, magnetic, and spin-dependent thermoelectric characteristics of X₂NbI₆ (X = Ga, In) vacancy-ordered perovskites. By calculating their tolerance factors, it was confirmed that these compounds exhibit cubic phase stability. From the volume optimization procedure, it was revealed that they are ferromagnetic. Additionally, the negative formation energies suggest that a thermodynamically stable form of X₂NbI₆ might be produced. The structural properties, namely the lattice constant and bulk modulus, were found to increase with the replacement of In instead of Ga at the X site. The electronic properties and integral values of total magnetic moments demonstrated the half-metallic nature of X₂NbI₆. The ferromagnetic nature and 100% spin polarizability revealed the feasibility of using X₂NbI₆ in the spintronic industry. The effective use of X₂NbI₆ as thermoelectric materials in the spin Seebeck effect was demonstrated by their spin-dependent thermoelectric properties.