Quantum dynamics of H2 in a carbon nanotube: Separation of time scales and resonance enhanced tunneling
Quantum dynamics of H2 in a carbon nanotube: Separation of time scales and resonance enhanced tunneling
M. Mondelo-Martell, F. Huarte-Larrañaga, U. Manthe.
J. Chem. Phys., 147 (2017) 084103.
Diffusion rates for H2 in a (8,0) carbon nanotube computed with TST (dotted line) and
flux correlation functions (solid line).
We study the diffusion of H2 in a narrow (8,0) carbon nanotube in the low pressure limit using quantum dynamics tools. Transmission coefficients for the elementary step of the transport process are calculated using the flux correlation function approach and diffusion rates are obtained using the single hopping model. We take advantage of the different time scales associated with the motion in the confined coordinates and the motion along the nanotube’s axis to develop an exact diabatic representation. An adiabatic approximation on the system, separating the dynamics of confined and unbound coordinates, agrees almost perfectly with the numerically exact simulation. Using it we study the dynamics up to 20 ps. Resonance enhanced tunnelling is found to be the dominant transport mechanism at low energies, increasing the diffusion rate at T<120 K.