| Popis: |
In this thesis we conduct a thorough study of the forces that act on ions when they are near air-water interfaces. These forces are important because they produce behavior which is very ion specific. That is, certain ions have a strong propensity for air-water interfaces and other ions avoid them completely. We will see that the dominant forces that allow ion adsorption to surfaces are fairly general and exist in a very broad class of liquids, so that even ions in a very simple model of a polar fluid exhibit a preference for the surface. In models of water, however, there are also forces which are very ion specific. In particular, the degree to which an ion is surface enhanced or surface repelled is very dependent on the sign of the charge. We will conduct a thorough study of this charge asymmetry in a simulated model of water and find that it is sensitive to various model details like ion size, the magnitude of the charge and polarizability. We will also study the way that solvent polarizability renormalizes the interactions between a pair of ions in solution, and a pair of ions at the interface and we will find that a simple effective model is fairly good at capturing the effects of polarizability. Finally, we will discuss attempts to improve dielectric continuum theory so that it is more useful for studying problems that involve solutes at interfaces. |
