Thermal expansion of carbon structures

Using an empirical bond-order potential, molecular dynamics (MD) simulations, and lattice dynamics calculations, we study the thermal expansion of diamond, graphite and single-walled carbon nanotubes. MD simulations demonstrate that, while the C-C bond length increases at a similar rate with increasing temperature in all structures, the thermal expansion coefficient varies greatly in a manner consistent with experiment. An analysis of the mode-dependent Gr\"uneisen parameters provides a detailed picture of how structure influences the competition between various vibrational modes associated with negative and positive Gr\"uneisen parameters in determining the overall thermal expansion coefficient.