First-Principles Investigation of the Structural, Electronic, and Thermoelectric Properties of YPtxNi1–xSb Half-Heusler Alloys with x = 0, 0.25, 0.50, 0.75, and 1

Abstract This study presents a comprehensive first-principles investigation of the structural, electronic, and thermoelectric properties of the YPtxNi1–xSb (x = 0, 0.25, 0.50, 0.75, 1) half-Heusler alloys, using density functional theory within the generalized gradient approximation (PBEsol). Our calculations of the lattice constant and bulk modulus for the parent compounds YNiSb and YPtSb show excellent agreement with available data. A key and unusual finding is the anomalous simultaneous increase in both the lattice parameter and the bulk modulus with rising Pt concentration, which deviates from the typical inverse correlation. Electronic band structure calculations reveal that all compositions are direct bandgap semiconductors. Furthermore, an analysis of the thermoelectric transport properties using the BoltzTraP code demonstrates high Seebeck coefficients and promising power factors for both p-type and n-type doping. The identified narrow direct bandgap in the YPtxNi1–xSb series suggests these materials are not only promising for efficient thermoelectric applications but also hold potential for infrared electronic and optoelectronic devices.