DFT study of structural, mechanical, electronic, and thermoelectric properties of YNbNi2X2 (X=Si or Ge) double half-Heusler alloy

Abstract

This work examines the structural, mechanical, electronic, and thermoelectric characteristics of YNbNi2X2 (X = Si, Ge) double half-Heusler alloys using density functional theory (DFT) computations. Thermodynamic stability was demonstrated by formation energy estimates, and mechanical parameters show ductile behavior with good mechanical stability. YNbNi2Si2 and YNbNi2Ge2 exhibit semiconducting characteristics, with indirect band gaps of 0.51 eV and 0.56 eV, respectively. The Boltzmann transport equation is used to investigate thermoelectric properties, which yield promising Seebeck coefficients and electrical conductivities. The dimensionless figure of merit (ZT) for YNbNi2Ge2 and YNbNi2Si2 peaks at 0.85 and 0.68 at 300 K respectively. However, these values should be regarded as upper limits, as only the electronic contribution to thermal conductivity was considered, and the lattice contribution was not explicitly calculated. The figure of merit (𝑍𝑇 ) increases with temperature suggesting that these are potential materials for energy harvesting applications at high temperature.