Low-dimensional peculiarities of vibrational characteristics and stability of graphene nanostructures
I.A. Gospodarev, V.A. Sirenko, E.S. Syrkin, S.B. Feodosyev
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
National Technical University “Kharkiv Polytechnic Institute”, 21 Bahaliy Str., Kharkov 61002, Ukraine
Received November 14, 2019, published online January 27, 2020
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.
Key words: graphite, graphene nanofilms, and nanotubes, defect, density of phonon states, phonon specific heat, mean square displacements of atoms, thermal expansion.