Density Functional Theory Investigations of Carbon Nanotube Unzipping on Cu(111)

The mechanism of carbon nanotube unzipping on a Cu(111) surface was investigated using density functional theory calculations. Optimized structures of armchair and zigzag carbon nanotubes of various sizes were considered, and their energies were compared to those of corresponding planar graphene nanoribbons. The results demonstrate that the flat configuration on the Cu(111) surface is energetically more favorable than the tubular one. As the nanotube diameter increases, the energy difference between the tubular and flat forms decreases due to the reduction in curvature of the nanotubes. Additionally, the energy gain associated with the transformation from nanotubes to nanoribbons is more significant for the zigzag-type structure than for the armchair-type one, suggesting that zigzag carbon nanotubes open more readily on Cu(111). Hypothetical intermediate states in the nanotube-to-nanoribbon transformation were also explored, providing valuable insights into the mechanism of this process.