For each BP polymorph, the mechanical properties were calculated (i) from the set of elastic constants C ij , and (ii) using three contemporary theoretical models of hardness . To verify the dynamic stability of BP phases, the calculations of the phonon bands have been performed. The approach consists of computing the phonon modes through finite displacements of the atoms off their equilibrium positions to subsequently obtain the forces from the summation over the different configurations. The phonon dispersion curves along the main lines of the respective Brillouin zone (BZ) were obtained using first-principles phonon calculation code "Phonopy" , and thermodynamic properties (Helmholtz free energy, heat capacity and entropy) were calculated as functions of temperature within the harmonic approximation. Finally, the electronic band structures showing small gap insulating behavior were assessed.