Probing the relationship between wall misalignment and water transport properties in sub-nm hexagonal boron nitride slit channels*

Recent advances in nanofabrication techniques are enabling the assembly of van der Walls (vdW) heterostructure-based artificial conduits of molecular sizes (with slit channel heights below 1 nm). As the characteristic length of a nanoconduit is decreased and becomes comparable to the atomic size of a confined fluid, surface effects dominate. In conduits with characteristic lengths smaller than 1 nm, interfacial effects become even more pronounced as a regime is reached wherein the bulk condition is no longer present, and the fluid becomes purely interfacial. Accordingly, the hydrodynamic properties of water in sub-nm confinement are highly influenced by the solid's crystallographic features and atomic nature. In this study, we probe the liquid-solid interfacial properties of water confined in sub-nm hexagonal boron nitride slit channels. Particularly, we conduct molecular dynamics to investigate how the lattice mismatch between the different layers comprising the nanochannel walls affects the resistance to water transport exerted by said channel. Simulation results show a significant relationship between wall misalignment and interfacial friction, which can be traced down to the morphology of the free energy landscape felt by a single water molecule at the solid surface.