Microscopic modeling of contact formation between confined surfaces in solution

Abstract: We derive a Kinetic Monte Carlo model for studying how contacts form between confined surfaces in an ideal solution. The model incorporates repulsive and attractive surface-surface forces between a periodic (2+1)-dimensional solid-on-solid (SOS) crystal surface and a confining flat surface. The repulsive interaction is derived from the theory of electric double-layers, and the attractive interactions are Van der Waals interactions between particles on the SOS surface and the confining surface. The confinement is induced by a constant external pressure normal to the surfaces which is in mechanical equilibrium with the surface-surface forces. The system is in thermal equilibrium, and particles can deposit to and dissolve from the SOS surface. The size of stable contacts formed between the surfaces in chemical equilibrium show a non-trivial dependency on the external pressure which is phenomenologically similar to the dependency of oscillatory hydration forces on the surface-surface separation. As contacts form we find classical phenomena such as Ostwald ripening, coalescence, and primary and secondary nucleation stages. We find contacts shaped as islands, bands or pits, depending solely on the contact size relative to the system size. We also find the model to behave well out of chemical equilibrium. The model is relevant for understanding processes where the force of crystallization and pressure solution are key mechanisms.