Lattice thermal properties of Graphane: thermal contraction, roughness and heat capacity

Using atomistic simulations we determine the roughness and the thermal properties of a suspended graphane sheet. As compared to graphene we found that hydrogenated graphene has: 1) a larger thermal contraction, 2) the roughness exponent at room temperature is smaller, i.e. $\simeq$ 1.0 versus $\simeq$ 1.2 for graphene, 3) the wave lengths of the induced ripples in graphane cover a wide range corresponding to length scales in the range (30-125),\AA at room temperature, and 4) the heat capacity of graphane is estimated to be 29.32$\pm$0.23,J/molK which is 14.8% larger than the one for graphene, i.e. 24.98$\pm$0.14,J/molK. Above 1500,K we found that graphane buckles when its edges are supported in the $x-y$ plane.