First-principles study of tantalum-arsenic binary compounds

The electronic properties and phase stability of binary tantalum arsenides are investigated using first-principles calculations. We find strong covalent bonding between Ta and As in TaAs2. In the lower As content compounds, the Ta is less covalent and donates charge to the As backbone. The covalency of other compounds becomes smaller with the increase of Ta composition. Compounds on the convex hull are TaAs2, TaAs, Ta5As4, and Ta3As, while Ta2As is slightly above the hull. Trends in the electronic and other properties are discussed. We identify the space group of TaAs2 to be centrosymmetric C2/m and find semimetallic behavior in TaAs and TaAs2. The other binary compounds are metallic systems with finite density of states at the Fermi level. The plasma energies show moderate conductivity anisotropy in Ta5As4 and Ta2As, which are also the most conductive compounds among the binary phases. Published by AIP Publishing.