Another example of quasi-linear EDMB is found in Sb atoms in SbPO4 . In this compound (see Fig. ), P is fourfold coordinated to O atoms in a sp 3 geometry typical of ionocovalent bonds. However, Sb is fourfold coordinated to O atoms, with two short and two long Sb-O bonds, forming a see-saw geometry as that of Fig. (note that Sb 3+ has a single LEP). The two short (long) bonds have ES= 1.0 (0.8) and both have ET≈ 0.65 (in good agreement with the ionocovalent Sn-O bond since Sn and Sb are neighbor atoms). This means that the short (long) bonds are located in the regions of covalent (EDMB) in Fig. . In summary, we tentatively conclude that our calculations of ES and ET suggest that MMBs in the Ah and Ai phases of group-15 and -16 elements are equivalent to the EDMBs of boranes since they are in the same region of the 2D map of Fig. , which is separated from the region occupied by molecules and molecular solids with ERMBs. It is important to stress that our view is different to the previous belief that electron-deficient (-rich) elements could only form electron-deficient (-rich) multicenter bonds.