For many years, the trans influence in the A7 structure of pnictogens was supposed to exist and invoked to explain the decrease of the frequencies of the optical phonons as well as the increase in the acoustic phonon frequencies and, consequently, the increase of the elastic constants at HP . The inverse behavior of ρd1 and ρd2 in As at stage 2 (above 16 GPa) can also be understood by the trans influence that results in a charge transfer from the primary covalent bond to the secondary bond as pressure increases until they reach the same value at Pt (once the MMBs are formed). This charge transfer is clearly shown by the evolution of ES of both primary and secondary bonds in As as pressure increases (Fig. ), as already mentioned.