2. Unconventional MMBs, as those present in PCMs and that we propose to be equivalent to EDMBs, are present in both the octahedrally-coordinated HP Ah and Ai phases of group-15 (As, Sb, Bi) and -16 (Se, Te) elements, respectively. Since these HP phases are not experimentally found in some of these elements, our results must be reinterpreted in a more general way: group-15 and -16 elements change in bonding from covalent ppσ-bonds plus secondary bonds to EDMBs as the octahedral atomic coordination is approached on increasing pressure. In particular, we propose that fully developed EDMBs occur in As-II above 25 GPa, in Sb-II above 8 GPa, in Bi-III above 2.7 GPa, in Se-V above 40 GPa, and Te-III above 8 GPa. Additionally, we propose that a mixture of covalent and EDMBs or even asymmetric EDMBs could also occur in intermediate HP phases, such as Bi-II above 2.5 GPa (Bi-II), in Se above 23 GPa (Se-III and Se-IV), and in Te-II above 4 GPa.