How do electronic properties of conventional III-V semiconductors hold for the III-V boron bismuth BBi compound?

We have performed ab-initio self-consistent calculations using the full potential linear augmented plane wave method to investigate the structural and the electronic properties of the boron bismuth III-V compound BBi. Our calculations provide the first available information about the structural and electronic ground-state properties of BBi. Total energy calculations of the cubic zinc-blende, wurtzite, rock-salt, cesium chloride and orthorhombic Cmcm phases are made. The zinc-blende structure is found to be the ground-state phase of BBi; within the generalized gradient approximation (local density approximation), we found a lattice constant of 5.529 angstrom (5.416 angstrom) and a bulk modulus of 72.20 GPa (86.27 GPa). We found that, contrary to other boron compounds, the band gap of BBi is direct at the F point. The relativistic contraction of the 6s orbital of Bi has a strong influence on the bands and bonds of BBi. Consequently, the electronic properties of BBi are shown to differ considerably from those of common group III-V semiconductors (e.g. GaAs); in particular, we found an unusually strong p-p mixing of the valence-band maximum relative to most of the other III-V compounds. Furthermore, the calculated valence charge density shows an anomalous behavior, characterized by a charge transfer towards the 'cation' B atom, further illustrating the rich behavior of boron bismuth compounds.