Atomistic Simulations of Solid-Liquid Interfaces

Abstract

Solid-liquid interfaces can be encountered in systems and processes ranging from biomineralization to fuel cell technology, and play an important role in growth or dissolution mechanisms of particles or surfaces in solution. The surface-induced changes of material properties not only affect the solid, but also the liquid itself: the structure of the liquid at the interface is very different from bulk. Understanding these processes occurring at solid-liquid interfaces at the atomistic scale is fundamental to a wide range of disciplines. New insight can be gained by combining cutting edge experimental techniques and computer simulations. The atomic force microscope (AFM) can be used to study solid-liquid interfaces in high resolution. We have developed new simulation methods, based on atomistic molecular dynamics and free energy calculations in order to model the complex imaging mechanism. In addition to the direct interactions between AFM tip and surface, our approach takes into account entropic contributions from interactions with water molecules in hydration layers on top of the surface as well as in the solvation shell of the AFM tip. For the Calcite (10-14) surface in water, we find good agreement between our simulations and recent 3D AFM data. We have also developed and tested a simple model to calculate AFM images only from differences in equilibrium local water density in hydration layers, reducing the computational cost by up to three orders of magnitude compared to free energy calculations including an explicit AFM tip. We have further studied the hydration layer structure and dissociation kinetics of the NaCl (100) surface in water from ab initio molecular dynamics, as well as the role of surface premelting of ice in the context of atomic scale friction at the ice-ice interface.