On the structure and electronic properties of Fe₂V_0.8W_0.2Al thin films

A very large thermoelectric figure of merit ZT = 6 at 380 K has recently been reported for Fe2V0.8W0.2Al in the thin-film form (B. Hinterleitner et al., Nature, 2019, 576, 85-90). In this form, Fe2V0.8W0.2Al experimentally crystallizes in a disordered A2 crystal structure, different from its bulk-form structure (L21). The first-principles calculations of the electronic structure performed in A2-Fe2V0.8W0.2Al supercells generated by the special quasirandom 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 μV 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.