A clearer comparison among all the studied pnictogens and chalcogens regarding the mechanism of MMB formation can be seen by plotting d1 and ρd1 vs. normalized d2 and normalized ρd2, respectively (Fig. ). This figure nicely shows the three (two) stages of the MMB formation mechanism in group-15 elements. Moreover, the strength of the secondary interaction along the three stages can be traced by the change in the background ground (from light blue to pink). The comparison of all elements in normalized values allows us to observe the relative decrease of the pressure range of both stages 1 and 2 in pnictogens and of stage 2 in chalcogens upon moving down the group (from As to Bi and from Se to Po), with the only exception of Bi due to the problems with the PBEsol calculations at HP previously mentioned. This outcome confirms our earlier observations of the pressure ranges of these stages in elemental pnictogens and chalcogens. Therefore, we conclude that the pressure-induced transformation from the pre-MMB scenario to the MMB scenario in group-15 elements proceeds via three (two) stages, being Po the only element of these two families whose two crystalline structures feature MMBs at RP. At this point, we want to stress that several questions regarding the mechanism of MMB formation are still not clearly understood and need further exploration: Why pnictogens show a three-stage mechanism and chalcogens only a two-stage one? Why the Ah phase is preferred by pnictogens at HP, while the Ai phase is preferred by chalcogens at HP? What is the relation between stage 2 in group-15 and -16 elements?