Melting of graphene: from two to one dimension
  The high temperature behaviour of graphene is studied by atomistic simulations based on an accurate interatomic potential for carbon. We find that clustering of Stone-Wales defects and formation of octagons are the first steps in the process of melting which proceeds via the formation of carbon chains. The molten state forms a three-dimensional network of entangled chains rather than a simple liquid. The melting temperature estimated from the two-dimensional Lindemann criterion and from extrapolation of our simulation for different heating rates is about 4900 K. 
K. V. Zakharchenko, Annalisa Fasolino, J. H. Los, M. I. Katsnelson
cond-mat.mtrl-sci