Calculation of Raman-active modes in linear and zigzag phases of fullerene peapods

We report on minimum energy calculations, using a convenient Lennard-Jones expression of the van der Waals intermolecular potential, to derive the optimum configurations of C-60 molecules inside single wall carbon nanotubes. Depending on the diameter of the nanotube, C-60 molecules were found to form linear or zigzag chains inside the nanotubes. In the following, we use the spectral moments method, together with a bond-polarizability model, to calculate the nonresonant Raman spectrum for infinitely long isolated C-60 peapods. We present the evolution of the Raman spectrum as a function of the diameter and chirality of the nanotube. The changes of the Raman spectrum as a function of the configuration of the C-60 molecules inside the nanotubes are identified. On the other hand, the effect of the filling factor on the Raman spectrum is analyzed. These predictions are useful to interpret the experimental Raman spectra of fullerene peapods.