Recent experimental characterization of alkali-metal atom adsorption in single-wall carbon nanotubes showed a softening of the Raman modes. To gain insight into the effects of K, Rb, and Cs doping, we report first-principles calculations of the Raman radial breathing and tangential $G$ modes. Structural parameters and charge transfer were examined in order to explain downshifts of the pertinent modes, well-reproduced theoretically. Our study serves as an example of the application of theory to provide justification for models used in interpreting experimental data.

• Received 6 April 2005

DOI:https://doi.org/10.1103/PhysRevB.72.121402