High-Throughput Exploration of Half-Heusler Phases for Thermoelectric Applications

Abstract

As a result of the high-throughput ab initiocalculations, the set of 34 stable and novel half-Heusler phases was revealed. The electronic structure and the elastic, transport, and thermoelectric properties of these systems were carefully investigated, providing some promising candidates for thermoelectric materials. The complementary nature of the research is enhanced by the deformation potential theory applied for the relaxation time of carriers (for power factor, PF) and the Slack formula for the lattice thermal conductivity (for figure of merit, ZT). Moreover, two exchange-correlation parametrizations were used (GGA and MBJGGA), and a complete investigation was provided for both p- and n-type carriers. The distribution of the maximum PF and ZT for optimal doping at 300 K in all systems was disclosed. Some chemical trends in electronic and transport properties were discussed. The results suggest TaFeAs, TaFeSb, VFeAs, and TiRuAs as potentially valuable thermoelectric materials. TaFeAs revealed the highest values of both PF and ZT at 300 K (PFp = 1.67 mW/K2m, ZTp = 0.024, PFn = 2.01 mW/K2m, and ZTp = 0.025). The findings presented in this work encourage further studies on the novel phases, TaFeAs in particular.

Machine Learning-Based Predictions for Half-Heusler Phases

“…The training subset of 47 18-valence electron hH phases considered in this work consists of 32 stable compounds (according to the Open Quantum Materials Database, OQMD [33]), as reported in the literature [34], and 15 systems with hull distance less or equal to 0.1 eV, which in many cases indicates stable phases (Aykol et al [35]). The 32 stable compounds were already comprehensively investigated as candidates for thermoelectric materials [4]. The structural and electronic properties of 15 additional phases are gathered in Table 1.…”

“…Half-Heusler (hH) phases continue to draw unwavering interest due to various possible applications, e.g., in optoelectronics [1,2], thermoelectric devices [1,3,4], and ferromagnets [5]. The stable hH compounds are limited to the 18 valence electron systems, i.e., ternary phases with stoichiometry of 1:1:1, XYZ (space group no F43m), where Z is a main group element, while X and Y are transition metals.…”