In stage 1 of As-I at 0 GPa (Fig. ), the larger pCOHP absolute values of the bonding bands (negative values of pCOHP ) as well as the larger IpCOHP and ICOBI(2c) values along d1 than along d2 indicate a much stronger bonding in primary than in secondary bonds, as already commented at the end of section 2. In addition, since negative (positive) values of ICOBI(3c) are interpreted to correspond to electron-rich or 3c-4e (electron-deficient or 3c-2e) interactions , the small, negative ICOBI(3c) value compared to the high ICOBI(2c) value along d1 seems to indicate that electron-rich three-center interactions are small in As-I at 0 GPa. In stage 2 of As-I at 20 GPa (Fig. ), the profiles of the pCOHP along d1 and d2 become more similar (both above and below the Fermi level). The decrease (increase) of the strength of primary (secondary) interactions due to the trans influence is reflected in the smaller (larger) values of the pCOHP than at 0 GPa. Moreover, the antibonding bands below the Fermi level along d1 (d2) show a smaller (larger) value of the pCOHP in comparison to As-I at 0 GPa. This can be interpreted as if the LEP in this stage experiences a much larger interlayer interaction (LEP-*) than intralayer interaction. We interpret this feature as the signature that the LEP starts to become inactive (non-stereoactive) with increasing pressure. The smaller and weaker (larger and stronger) primary (secondary) bonds in stage 2 than in stage 1 due to trans influence are also reflected in the smaller (larger) values of IpCOHP(2c) and ICOBI(2c) along d1 (d2) . Moreover, the ICOBI(3c) value at 20 GPa shows a much larger negative value than at 0 GPa which seems to be consistent with the process of multicenter bond formation in As at HP. Finally, pCOHP profiles are similar for the primary and secondary bonds in As-I at 35 GPa (Fig. ) as expected for MMBs in stage 3. The slightly different profiles for both bonds are due to the slight distortion of the cubic symmetry in As-I with respect to As-II at 35 GPa, as already mentioned (both pCOHP profiles are exactly equal in As-II at 35 GPa, see Figure in ESI).