Designing graphene origami structures with a giant isotropic negative coefficient of thermal expansion

Materials with an isotropic negative coefficient of thermal expansion (CTE) of the order of K−1 are rare, and almost all of them are porous. Using molecular dynamics simulations, we show that graphene origami structures obtained by pattern-based hydrogenation can exhibit a negative CTE. The magnitude and anisotropy of the CTE can be controlled by parameters of the pattern-based hydrogenation that determine the stiffness and Poisson ratio, respectively. We achieve an isotropic CTE of K−1, which is an enhancement by three orders of magnitude as compared to reports for other graphene-based structures and comes close to the record of all known materials.