where E 0 , V 0 , B 0 and B 0 ʹ are the equilibrium energy, volume, bulk modulus and its first pressure derivative, respectively. As can be seen from the Fig. , for all boron pnictides the polymorphs with crb topology are metastable over the whole range of experimentally accessible pressures. However, the closeness of the cohesive energies of zinc-blende and crb polymorphs (see Table ) allows for the possibility of formation of crb BX at high pressures and high temperatures as a result of alternative metastable behavior, most likely in chemical reactions of the elements.