Low-dimensional peculiarities of vibrational characteristics and stability of graphene nanostructures
For graphite and graphene nano-formations: nanofilms, and nanotubes at the microscopic level, the densities of phonon states and the associated vibrational thermodynamic characteristics are calculated and analyzed: specific heat, mean square displacements of atoms and thermal expansion. The calculation model is based on experimental data without using a priori assumptions about the nature and potentials of interatomic interactions and only then is compared with them, demonstrating good agreement. The quasi-flexural mode inherent to graphene structures and the rotation mode characteristic of graphene nanotubes are investigated, and their contributions to low-temperature vibrational characteristics are analyzed. The effect on the phonon spectrum and vibrational characteristics of some extended defects is analyzed: graphite intercalation by transition metals, steps on the surface of graphene nanofilms and the boundaries of the graphene monolayer sample on the substrate. The calculation results are compared with experimental data.