The half-metallic, mechanical, and transport properties of the quaternary Heusler compound of PdZrTiAl is discussed under hydrostatic pressures in the range of –11.4 GPa to 18.4 GPa in the framework of the density functional theory (DFT) and Boltzmann quasi-classical theory using the generalization gradient approximation (GGA). By applying the stress, the band gap in the minor spin increases so that the lowest band is obtained 0.25 eV at the pressure of –11.4 GPa while the maximum gap is calculated 0.9 eV at the pressure of 18.4 GPa. In all positive and negative pressures, the PdZrTiAl composition exhibits a half-metallic behavior 100% spin polarization at the Fermi level. It is also found that applying stress increases the Seebeck coefficient in both spin directions. In the minority spin, the n-type PdZrTiAl, the power factor (PF) for all the cases is greater in the equilibrium state than the strain and stress conditions whereas in the majority spin, the PF value of the stress state is greater than the other two. The non-dimensional figure of merit (ZT) is significant and is about one in spin down in the room temperature for the all pressure states that it remains on this value by applying pressure. The obtained elastic constants indicate that the PdZrTiAl crystalline structure has a mechanical stability. Based on the Yong (E), Bulk (B) and shear (G) modulus and Poisson (n) ratio, the brittle-ductile behavior of this compound has been investigated under pressure. The results indicate that PdZrTiAl has a ductile nature and it is a stiffness compound in which elastic and mechanical instability increases by applying strain.

In this work, the electronic structure and optical behavior and the thermoelectric performance of the known HfNiSn compound have been studied under the substitution of Mn transition metal instead of Ni atoms. Necessary calculations are performed in the framework of DFT first principles studies by applying generalized gradient approximation (PBE-GGA) as well as solving Boltzmann’s semi-classical equations. The entering Mn leads to a change in the electronic structure of HfNiSn and the occurrence of half-metallic ferromagnetic behavior with 100% polarization at the Fermi level. The maximum ZT value obtained for HfMnSn shows that HfNiSn would be suitable for thermoelectric applications at room temperature, both in pure and Mn presence. The examination of optical parameters also indicates good absorption in the visible range for this compound in all cases.