A deeper understanding of chemical bonding in As can be obtained from the reciprocal-space (band) picture , since the three stages of As can be distinctively characterized by orbital-based methods. The electronic bands and DOS of As-I at 0 GPa have been thoroughly discussed in the literature and are briefly commented on in section 6 of the ESI. Here we analyze the pCOHP (Fig. ) and COBI (Fig. in ESI) as well as their integrated values (IpCOHP, ICOBI(2c), and ICOBI(3c)) along the d1 and d2 bonds in As-I at 0, 20, and 35 GPa that correspond to stages 1, 2, and 3, respectively. The most important point is that bands with antibonding character (positive value of pCOHP ) appear below the Fermi level both along d1 and d2 at RP, as well as in Te-I . These bands come from the interaction between the LEP and the bonding orbital of the covalent bond (along d1) and between the LEP and the antibonding orbital of the covalent bond (along d2), as already discussed by Hoffmann and coworkers . The antibonding character of these bands, in which LEPs are involved, comes from the s-p mixing, i.e., the mixing of the s-type electrons of the LEP and the p-type electrons of the bonding and antibonding orbitals of the covalent bond .