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"Ab initio density functional calculations are performed for a toroidal carbon C 120 nanostructure doped with one to ten calcium atoms bonded to its outer surface. The calculations are based on DFT with the generalized gradient approximation PW91 (Perdew and Wang) as implemented in the Materials Studio v.4.3 code. Dmol 3 module is used to calculate, among others, total energies, charge density, HOMO- LUMO and Mulliken population analysis. Based on these results, it is possible to propose that a single Ca atom is able to adsorb up to 6 H 2 molecules. The study is extended for a system with ten Ca atoms, which can adsorb up to 60 H 2 molecules. This leads to 6.16 weight percentage for the gravimetric hydrogen storage capacity which fulfills the US Department of Energy (DOE) target (6 wt%) for onboard hydrogen storage systems for the year 2010. Accordingly, the calcium-coated toroidal carbon C 120 nanostructure is a good quality candidate for H 2 storage with higher adsorption energy than on pristine carbon nanotorus."

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 HH are 0.753 and 0.772 A 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 HC bondings with bond length close to that in methane. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2495–2508, 2010