Using the crystal parameters in Table , the electronic band structures were calculated using the allelectrons DFT-based augmented spherical method (ASW) . The results are shown in Fig. . The bands (blue lines) develop along the main directions of the respective Brillouin zones, i.e. cubic for zb-BX and hexagonal for qtz BX. In all panels, except for Fig. corresponding to qtz BBi, the zero energy along the vertical axis is considered with respect to E V , at the top of the filled valence band (VB), separated from the empty conduction band (CB) by a small band gap. For all three boron pnictides, the zinc-blende phases have larger band gaps compared to the qtz phases. The smaller magnitudes for the latter result from the smaller volumes per formula unit, leading to an increased covalence, as shown above with the Pauling electronegativity values  and their differences  for the considered boron pnictides. A relevant feature appears for qtz BBi, which behaves as a metal with the energy reference at the Fermi level E F . The transition from semiconducting zb-BBi to metallic qtz BBi can be proposed to explain the dynamic instability observed from the phonons.