Anomalous pressure behavior of tangential modes in single-wall carbon nanotubes

Using molecular-dynamics simulations and the force-constant model, we have studied the Raman-active tangential modes (TMs) of a (10,0) single-wall carbon nanotube under hydrostatic pressure. With increasing pressure, the atomic motions in the three TMs present obvious diversities. The pressure derivative of E-1g, A(1g), and E-2g mode frequencies shows an increased value (d omega(E1g)/dP>0), a constant value (d omega(A1g)/dP similar to 0), and a negative value (d omega(E2g)/dP < 0) above 5.3 GPa, respectively. The intrinsic characteristics of TMs consumedly help us understand the essence of the experimental T band of CNT. The anomalous pressure behavior of the TM frequencies may originate from the tube symmetry alteration from D-10h to D-2h then to C-2h.