A first-principles computational study has explored the potential of quaternary Heusler alloys LiHfIrZ (where Z can be Si or Ge) for thermal energy harvesting. These alloys have shown promising properties for thermoelectric applications, which allow for the direct conversion of waste heat into electricity. The research focused on evaluating key parameters such as structural stability, electronic properties, and thermoelectric performance of these compounds, seeking efficient materials for energy conversion.

Calculations revealed that both alloys, LiHfIrSi and LiHfIrGe, are stable in their crystalline structure. From an electronic perspective, they are classified as semiconductors with indirect band gaps. Specifically, LiHfIrSi exhibits a band gap of 0.45 eV, while LiHfIrGe has one of 0.38 eV. These band gaps are crucial for thermoelectric performance, as they allow for a balance between electrical and thermal conductivity. The results also indicate that the substitution of Si with Ge in the alloy does not significantly alter the nature of the band gap.

The study also examined the power factor and phonon thermal conductivity, two fundamental parameters for determining the efficiency of a thermoelectric material. It was found that these alloys possess a relatively high power factor and low phonon thermal conductivity, suggesting a promising figure of merit (ZT). A high ZT is indicative of good thermoelectric energy conversion efficiency. These findings position LiHfIrZ alloys as viable candidates for the development of thermal energy harvesting devices, opening new avenues for waste heat recovery.