Following the same strategy as with elemental As, we have simulated the effect of pressure on the A7 phases of Sb (Sb-I) and Bi (Bi-I) (see Fig. and S4 in ESI). As already mentioned, the A7 phases of Sb and Bi also tend to transform to the Ah phase. Interestingly, this phase has not been observed in Bi at HP, although the monoclinic Bi-II phase is a slightly distorted sc phase, and it remains uncertain whether it exists or not in Sb (see discussion in section 2 of ESI). In any case, we have calculated the A7-to-Ah PT in both elements because it provides valuable insight to clarify the nature of the MMB and the various stages of the pre-MMB to MMB transformation discussed in the next sections.