Exploration of Multi-Component Vanadium and Titanium Pnictides Using Flux Growth and Conventional High-Temperature Methods.

The flux growth method was successfully employed to synthesize millimeter-sized single crystals of the ternary barium vanadium pnictides BaVAs ( ≈ 0.02) and BaVSb ( ≈ 0.36), using molten Pb and Sb, respectively. Both compositions crystallize in space group 3 and adopt a structure similar to those of the barium titanium pnictides BaTi ( = Sb, Bi), yet with a subtly different disorder, involving the pnictogen and barium atoms. Attempts to obtain an arsenide analog of BaTi using a Pb flux technique yielded binary arsenides. High-temperature treatment of the elements Ba, Ti, and As in Nb or Ta tubes resulted in side reactions with the crucible materials and produced two isostructural compositions BaTi As ( = Nb, Ta; ≈ 4), representing a new structure type. The latter structure displays -type metal clusters comprised of statistically distributed Ti and atoms ( = Nb, Ta) with multi-center and two-center bonding within the clusters, as suggested by our first-principle calculations.