Accelerated Discovery of New 8-Electron Half-Heusler Compounds as Promising Energy and Topological Quantum Materials

Rapid discovery of potential functional materials remains an open challenge. We often focus on exploring the properties of previously reported compounds, but avoid various unreported but chemically plausible compounds that might have promising properties. Here, we present a high throughput ab initio study of the I-III-IV class of half-Heusler alloys with 8 valence electrons, in the quest of finding potential (i) thermoelectric, (ii) topological insulating, and (iii) optoelectronic materials. Of various classes, 8-electron half-Heusler compounds are least studied, and hence our choice. By carefully choosing reliable and accurately simulated descriptors (such as formation energy, phonon dispersion, accurate band gaps), we have discovered 21 semiconducting compounds. Out of these 21 compounds, 6 were found to show excellent thermoelectric performance (figure of merit ZT > 0.8); other range from ZT = 0.2 to 0.8. Seventeen compounds were found to show robust topological insulating behavior confirmed by bulk band inversion, and surface conducting states. Two compounds show a relatively large band gap and can be promoted for possible optoelectronic applications with further band engineering. Our search model opens new avenues for the discovery of more novel materials in different and unexplored classes of systems. We strongly propose the experimental characterization of the above promising compounds to shed more light on the present findings.