Molecular‐Dynamics Simulation of Self‐Diffusion of Molecular Hydrogen in X‐Type Zeolite

Abstract

The self-diffusion of hydrogen in NaX zeolite has been studied by molecular-dynamics simulations for various temperatures and pressures. The results indicate that in the temperature range of 77-293 K and the pressure range of 10-2700 kPa, the self-diffusion coefficients are found to range from 1.61 × 10 −9 m 2 ⋅s −1 to 3.66 × 10 −8 m 2 ⋅s −1 which are in good agreement with the experimental values from the quasielastic neutron scattering (QENS) and pulse field gradients nuclear magnetic resonance (PFG NMR) measurements. The self-diffusion coefficients decrease with increasing pressure due to packing of sorbate-sorbate molecules which causes frequent collusion among hydrogen molecules in pores and increase with increasing temperature because increasing the kinetic energy of the gas molecules enlarges the mean free path of gas molecule. The activated energy for hydrogen diffusion determined from the simulation is pressure-dependent.

Transfer-Free CVD Growth of High-Quality Wafer-Scale Graphene at 300 °C for Device Mass Fabrication

“…At a low chamber pressure, carbon atoms experience very little resistance during diffusion because the concentration of gas molecules and reactive radicals is low, and the scattering that occurs on the Cu surface is weak. This is consistent with the conclusion obtained by Ranieri et al and Du et al , They used quasi-elastic neutron scattering measurements and molecular dynamics simulations to confirm that the diffusion coefficient increases with decreasing pressure. Nevertheless, if the pressure is too low, for instance, dropped to 10 Pa, then the low concentration of carbon source in the chamber causes insufficient carbon atoms to be adsorbed on the Cu surface, and graphene cannot be synthesized (Figure S4).…”

Study on the Separation of H2 from CO2 Using a ZIF-8 Membrane by Molecular Simulation and Maxwell-Stefan Model

“…Figure 4 displays the MSD as a function of time for both H 2 and CO 2 molecule diffusion in the ZIF-8-based membrane at 298 K and for a set loading of 10 molecules/cell. The relationship between the observed MSD versus time is linear, with a very good approximation, as also observed in other works in the literature [31,32].…”