The interaction between atomic-scale pores and particles.

Using first-principles calculations for angstrom-sized pores (3-10 Å), we investigate pore-particle interaction. The translocation energy barrier (TEB) plays important role for the angstrom-scale pores created in 2D-materials such as graphene which is calculated for the translocation of rare gases (He, Ne, Ar, Xe), diatomic molecules (H2and N2), CO2, and CH4. The critical incident angle (the premeance beyond that is zero) was found to be 40°, which is different from classical model's prediction of 19-37°. The calculated TEB (Δ) and the surface diffusion energy barrier (Δ') for the particles with small kinetic diameter (He, Ne and H2), show that the direct flow is the dominant permeation mechanism (Δ ≈ 0 and Δ' > 30 meV). For the other particles with larger kinetic diameters (Ar, Kr, N2, CH4and CO2), we found that both surface diffusion and direct flow mechanisms are possible, i.e. Δ and Δ' ≠ 0. This work provides important insights into the gas permeation theory and into the design and development of gas separation and filtration devices.