Molecular Mechanics of the Fluid-solid Interface

Gerald Wang, Massachusetts Institute of Technology

Near a fluid-solid interface, fluids can exhibit significant structuring effects, which manifest as non-uniform spatial density profiles. In particular, at the fluid-solid interface, fluids often adopt a layered structure, which can significantly affect transport properties at the interface. We will present several results from molecular-mechanical modeling and molecular-dynamics simulations with the goal of understanding the structure of the first fluid layer directly adjacent to the solid. We will show that the key features of this layer – including its separation distance from the solid, its width and its areal density (defined as the number of atoms per unit of fluid-solid interfacial area) – can be accurately described as functions of the molecular properties of the fluid, the system temperature and the system-averaged fluid density. Moreover, we will show that for dense fluids, we exhibit a scaling relationship relating the areal density and the width of the first layer to the average fluid density. We will demonstrate the broad applicability of these results to fluid-solid interfaces under nanoconfinement. We will also discuss the validity of our results under different choices of thermal boundary conditions, strengths of fluid-solid interaction and wall geometries. These results are directly applicable to the development of models for nanoscale heat, mass and momentum transport.

Abstract Author(s): Gerald J. Wang