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 (i) hydrogenated graphene has a larger thermal contraction, (ii) the roughness exponent at room temperature is smaller, i. e., similar or equal to 1.0 versus similar or equal to 1.2 for graphene, (iii) the wavelengths of the induced ripples in graphane cover a wide range corresponding to length scales in the range 30-125 angstrom at room temperature, and (iv) the heat capacity of graphane is estimated to be 29.32 +/- 0.23 J/mol K, which is 14.8% larger than that for graphene, i. e., 24.98 +/- 0.14 J/mol K. Above 1500 K, we found that graphane buckles when its edges are supported in the x-y plane.