Fe2HfZ (Z = Si, Ge, Sn), Promising New Candidate Materials for Electronic and Thermoelectric Applications

Full-Heusler materials have attracted intensive attention of scientific research in recent years due to their physical properties, the materials are considered potential candidates for high performance thermoelectric applications. Structural, elastic, and electronic properties of full-Heusler Fe2HfZ (Z = Si, Ge, Sn) compounds have been studied using a pseudopotential plane-wave method within the framework of density functional theory, the exchange correlation effects have been treated using the generalized gradient approximation GGA-PBEsol as implemented in the CASTEP code. The calculated results for lattice constant, bulk modulus (B) and its pressure derivative \(B_{0}{\prime}\) are in good agreement with the theoretical data. We have calculated the elastic constants and checked the mechanical stability of the Fe2HfZ (Z = Si, Ge, Sn) materials. Fe2HfZ (Z = Si, Ge, Sn) are found to be mechanically stable. Independent single-crystal elastic properties like bulk modulus, shear modulus, Young’s modulus and universal index for the corresponding polycrystalline phase indicate that Fe2HfZ (Z = Si, Ge) are brittle and Fe2HfSn is ductile. The values of Young’s modulus demonstrate that, among the investigated materials, Fe2HfSi is the stiffer one. The universal anisotropy index differs significantly from zero, indicating that our materials are elastically anisotropic. We also calculated electronic band structures, total and partial electronic density of states. According to our calculations, Fe2HfZ (Z = Si, Ge, Sn) compounds are not spin polarized. While Fe2HfSn have a metallic behavior, Fe2HfSi and Fe2HfGe exhibit a semiconductor behavior with indirect band gaps of 0.325 eV and 0.097 eV respectively. The partial densities of states show that the valence bands due to Fe-d orbitals and the conduction band due to Fe-d and Hf-d orbitals.