Are deformed modes still Raman active for single-wall carbon nanotubes?

Using group theory calculations combined with the force-constant model and molecular-dynamics simulations, whether the deformed modes are Raman active or not for (10,10) and (10,0) single-wall carbon nanotubes under hydrostatic pressure is discussed. With increasing pressure, the tube symmetry lowers from D20h to D2h then to C2h point group. For D20h, A1g is changed to Ag, while E1g and E2g are split: E1g→B2g+B3g→2Bg and E2g→Ag+B1g→2Ag. On the basis of the correlation between D20h, D2h, and C2h point groups, the deformed modes should be still Raman active. The result can help us clarify the essence of the experimental observations.