The simulated atomic volume, lattice parameters, and phonon frequencies of Sb-I and Bi-I as a function of pressure show in general better agreement with the experiment than for As-I. These results suggest that anharmonic effects are less pronounced in Sb and Bi than in As although these elements at RP show bonds that are closer to the MMBs than in As, as we will discuss later. Again, the presence of MMBs in the Ah phase in Sb and Bi is confirmed by the change in the sign of the pressure coefficients of the optical phonon frequencies, the high value of |γi| near Pt, the increase of the Z* in the A7 phase and its high value in the octahedrally-coordinated Ah phase, and by the negligible value of the ∇ 2 ρ in the Ah phase. Therefore, despite that the Ah phase could not be experimentally observed in these compounds at HP, it can be concluded that both Sb and Bi tend to exhibit unconventional MMBs as pressure increases and octahedral coordination is approached.