Mechanical stability and thermoelectric properties of the PdZrTiAl quaternary Heusler: A DFT study

Abstract The study of half-metallic behavior, thermoelectric properties and thermodynamic stability of the new quaternary PdZrTiAl Heusler were carried out based on the Density Functional Theory (DFT) calculations. The generalized gradient approximation with Tran-Blaha potential (GGA + mbJ) was utilized to treat the exchange-correlation energy for the calculations of electronic structures. More accurate results of the dynamic stability investigation of the intended Heusler compound were obtained by using and Quantum Molecular Dynamic (QMD) simulation. Calculation of the electronic structure indicates that the PdZrTiAl compound has an indirect band gap 0.69eV (from GGA + mbJ) in the down spin and therefore is a ferromagnetic half-metal with 3.00μB magnetic moment. The investigation of the thermodynamic phase diagram showed that this material is stable in all thermodynamic conditions. Furthermore, the phonon positive frequencies and the results of QMD, confirms the sustainability of this structure in XX΄YZ stoichiometric compound. The elastic constants reveal that the PdZrTiAl are mechanically stable and the Poisson's ratio confirmed that the alloys considered are ductile. Also, thermoelectric properties of this compound were studied using transport quasi-classical theory. It was observed that in two majority and minority spin states, this combination shows an utterly distinct thermoelectric behavior. This compound has a good merit coefficient at dn spin at all temperature ranges, especially at low temperatures and the negative sign of the Seebeck coefficient indicates that electrons are charge carriers.