Numerical analysis of the radial breathing mode of armchair and zigzag single-walled carbon nanotubes under deformation

An ab initio analysis based on the density functional theory is carried out to investigate the effects of axial strain and radial pressure on the radial breathing mode (RBM) frequency of individual single-walled carbon nanotubes with armchair and zigzag chiralities. It is found that the RBM frequency is not sensitive to axial tensile strain or small axial compressive strain. When the axial compressive strain exceeds a critical value, the RBM frequency is significantly reduced. On the other hand, the RBM frequency is highly sensitive to the radial pressure; a pressure of 1 GPa can increase the RBM frequency by about 8 cm^-1. Under a high radial pressure, the difference between the frequencies of the positive and negative half periods of the RBM vibration sharply increases, which may lead to the separation of the RBM peaks. Very good agreement is found between the present numerical analysis and previous experimental results. © 2006 American Institute of Physics.