84 research outputs found
Effect of the benzyl groups on the binding of H2 by three-coordinated Ti complexes
Using first-principles calculations, we investigate the adsorption of H2
molecules on a three-coordinated benzyl-decorated titanium complex suggested in
a recent experiment [Hamaed et al., J. Am. Chem. Soc. 130, 6992 (2008)]. Unlike
the interpretation of the experimental results that the Ti(III) complex can
bind five H2 molecules via the Kubas interaction, the Ti(III) complex cannot
adsorb H2 molecules via the Kubas interaction. In contrast, a benzyl-released
Ti(III) complex can adsorb up to two H2 molecules with a binding energy of
~0.25 eV/H2 via the Kubas interaction, in good agreement with the measurement
of ~0.2 eV. The calculated occupation number of H2 molecules at 25 oC and -78
oC under 60 atm is 0.9 and 1.9, respectively, in good agreement with the
measurement of 1.1 and 2.4 near the conditions, respectively. Our results
suggest that the Ti complex in experiment might be a benzyl-released form.Comment: 11 pages, 3 figures, to appear in Phys. Rev.
Preferential functionalization on zigzag graphene nanoribbons: First-principles calculations
We investigate the functionalization of functional groups to graphene
nanoribbons with zigzag and armchair edges using first principles calculations.
We find that the formation energy for the configuration of the functional
groups functionalized to the zigzag edge is ~0.2 eV per functional group lower
than that to the armchair edge. The formation energy difference arises from a
structural deformation on the armchair edge by the functionalization whereas
there is no structural deformation on the zigzag edge. Selective
functionalization on the zigzag edge takes place at a condition of the
temperature and the pressure of ~25 oC and 10-5 atm. Our findings show that the
selective functionalization can offer the opportunity for an approach to the
separation of zigzag graphene nanoribbons with their solubility change
Ab initio study of beryllium-decorated fullerenes for hydrogen storage
We have found that a beryllium (Be) atom on nanostructured materials with H2
molecules generates a Kubas-like dihydrogen complex [H. Lee et al.
arXiv:1002.2247v1 (2010)]. Here, we investigate the feasibility of Be-decorated
fullerenes for hydrogen storage using ab initio calculations. We find that the
aggregation of Be atoms on pristine fullerenes is energetically preferred,
resulting in the dissociation of the dihydrogen. In contrast, for boron
(B)-doped fullerenes, Be atoms prefer to be individually attached to B sites of
the fullerenes, and a maximum of one H2 molecule binds to each Be atom in a
form of dihydrogen with a binding energy of ~0.3 eV. Our results show that
individual dispersed Be-decorated B-doped fullerenes can serve as a
room-temperature hydrogen storage medium.Comment: 11 pages, 3 figures, Accepted for publication in Journal of Applied
Physic
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