On the structure and electronic properties of Fe2V0.8W0.2Al thin films

A very large thermoelectric figure of merit ZT = 6 at 380 K has recently been reported in Fe2V0.8W0.2Al under thin-film form (Ref. 1, Hinterleitner et al., Nature 576 (2019) 85). Under this form, Fe2V0.8W0.2Al experimentally crystallizes in a disordered A2 crystal structure, different from its bulk-form structure (L21). First principles calculations of the electronic structure performed in A2-Fe2V0.8W0.2Al supercells generated by the Special Quasi-random Structure (SQS) method are thus reported here. These calculations unambiguously indicate that A2-Fe2V0.8W0.2Al is a ferromagnetic metal at 0 K, displaying a small Seebeck coefficient at 400 K (< 30 microV K-1). The present results contradict the scenario of the occurrence of a deep pseudo-gap at the Fermi level, previously invoked to justify ZT = 6 in Fe2V0.8W0.2Al thin films.