The fundamental point is that the mechanism of EDMB formation in B2H6 is the same as that of MMB formation in the group-15 and -16 elements at HP, as shown in the previous section. In both cases, there is a charge transfer from the primary bond to the secondary one that softens and enlarges the primary covalent bond. The loss of charge of the primary covalent bond is the reason for the small value of ES in MMBs and EDMBs once they are formed. Curiously, this mechanism seems to be exactly the same mechanism of intermolecular, secondary bonding that occurs in the formation of polymeric CO2 phases and in the atomic/polymeric phases of elemental nitrogen and hydrogen at HP . For instance, the anomalous increase (decrease) of the intramolecular (intermolecular) H-H distance in H2 as pressure increases above 100 GPa is caused by the charge transfer from intramolecular to intermolecular bonds that ends once both bond distances equalize, and each bond in the atomic/polymeric phase has a single electron per atom pair, i.e. all H-H bonds are 2c-1e bonds . Noteworthy, the charge transfer in hydrogen from the intramolecular H-H bond towards the intermolecular H-H bond is out of any doubt since the two electrons of the H2 molecule at RP are between the two H atoms of the H2 molecule and there is only one electron per H atom (no LEPs involved). Therefore, it seems that the atomic/polymeric phases (stage 3) of elemental hydrogen, supposed to exist above 500 GPa and discussed in the previous section, is also characterized by 2c-1e bonds, similar to EDMBs and MMBs. in ESI.