Hydrogen storage inside a toroidal carbon nanostructure C₁₂₀: Density functional theory computer simulation

Ab initio density functional calculations were performed for a toroidal carbon C₁₂₀ nanostructure. Hydrogen molecules, n = 1-15, were added inside the nanotorus and for each one of these systems a geometry optimization was obtained. The cohesive energy shows that these structures are energetically stable. For example, the binding energies are -34.95 and -36.19 Hartrees and the interatomic distances H-H are 0.753 and 0.772 Å for 1 and 14 molecules, respectively. Considering only molecular hydrogen, we have always seen so far weak physisorption into the C₁₂₀ nanotorus. There is no chemisorption until the number oh hydrogen molecules are increased to 14. In this case, four hydrogen atoms are chemisorbed. With 15 molecules, there are 10 hydrogen atoms chemisorbed just at the inner nanotorus surface forming 10 H-C bondings with bond length close to that in methane.