Lattice Dynamics of Potassium-Doped Single-Walled Carbon Nanotubes

We calculate the vibrational properties of potassium-doped single-walled carbon nanotubes within lattice dynamical theory. The results show that the frequency of high-frequency Raman mode E_2g for K₅C₄₀ downshifts to 1553 cm^-1, which is in agreement with the value for highly doped samples with effective composition KC₈. Moreover, the specific heat curves have a turnover at 22 K, originating from the saturation of K atoms vibrational modes at low energy.