5D quantum dynamics of the H2@SWNT system: Quantitative study of the rotational-translational coupling

Abstract

The dynamics of the dihydrogen molecule when confined in carbon nanotubes with different chiralities and diameters are studied by using a 5 dimensional model considering the most relevant degrees of freedom of the system. The nuclear eigenstates are calculated for an (8,0) and a (5,0) carbon nanotubes by the State-Average Multiconfigurational Time-dependent Hartree, and then studied using qualitative tools (mapping of the total wave functions onto given subspaces) and more rigorous analysis (different kinds of overlaps with reference functions). The qualitative analysis is seen to fail due to a strong coupling between the internal and translational degrees of freedom. Using more accurate tools allows us to gain a deeper insight into the behaviour of confined species. C 2015 AIP Publishing LLC. [http://dx

Diffusion of H2 and D2 Confined in Single-Walled Carbon Nanotubes: Quantum Dynamics and Confinement Effects

“…Instead, several sets of LJ parameters have been used in the past to model the C–H interactions in a nanotube. Among the available LJ parameters, we have first selected a set used by us in our recent work, ,, with σ = 2.82 Å and ϵ = 0.0605 kcal/mol (this potential will referenced as ref PES). Additionally, motivated by the large differences between the different potentials reported by Garberoglio et al, we have also used a second potential for our calculations.…”

“…For instance, dangerous pollutants or greenhouse effect compounds can be kept off the atmosphere, or clean fuels such as hydrogen can be transported from production to consumption sites, thus spreading its use. ,− The study of these substrate–gas systems has led to the discovery of quantum confinement effects, distortions of the molecular structure arising from the encapsulation in cavities of the order of the nanometer . These effects have opened a new field of research that tries to understand them to design novel and better storage devices − and find new technological applications. These applications include isotopic separation of compounds, either by selective adsorption , or kinetic effects, to nanoconfined tailored reactions. − …”

“…For instance, the model relies on the full separability of all the DOFs, which is known to be too harsh an assumption on nanoconfined systems. 18,22,23 For this reason, q con is actually calculated as the trace of the Boltzmann operator of the confined 5D Hamiltonian,Ĥ con (ρ, θ, φ, x, y). This operator is equivalent to the one in Eq (3) but fixing the position along z at a -1.36 bohr, corresponding to an energy minimum.…”

“…Instead, several sets of Lennard-Jones parameters have been used in the past to model the C-H interactions in a nanotube. Among the available Lennard-Jones parameters, we have first selected a set used by us in our recent work, 18,22,48 with σ = 2.82Å and = 0.0605 kcal/mol (this potential will referenced as Ref.…”

Quantum dynamics of H2 in a carbon nanotube: Separation of time scales and resonance enhanced tunneling

“…7,[23][24][25][26][27][28] One particular feature present in single-walled carbon nanotubes (SWCNTs) that makes them especially interesting materials is their cylindrical shape, which gives rise to the coexistence of a 2D confinement in the space perpendicular to the nanotube's axis and unbound motion along this latter coordinate. Even though 2D confinement has been relatively studied and reviewed in the literature, 12,16,29,30 only few studies have treated both the confined and the quasi-free coordinates in a fully quantum formalism. To the best of our knowledge, only Skouteris and Laganá, 31 treating the motion of an OH radical along a (10,0) SWCNT, and some of the present authors, 32,33 dealing with the H 2 molecule in a (8,0) SWCNT, have performed such studies.…”