The Relationship Between Reactivity and Topography of Crystal Surfaces

Understanding weathering processes at solid interfaces requires a combination of both experimental and theoretical approaches. The impact of experimental results depends on our ability to vary observational scales at will. This approach allows us to understand the occurrence and importance of spatial anisotropy of alteration reactions. We apply super-resolution principles in concert with subpixel sample positioning to achieve an unprecedented enhancement in the spatial resolution of a vertical scanning interferometer.

In a preliminary application of this new approach, we resolve monolayer features of dissolving calcite surfaces and sub-micron etch pit formation in natural glass at macroscopic fields of view. We evaluate the evolution of surface roughness parameters and associated dissolution rates. In a complementary effort to achieve a fundamental understanding of the relationship between surface topography and reactivity, we extend these results to the molecular scale. We explore the evolution of surface reactivity through crystal-accurate Monte-Carlo simulations of dissolution reactions. These simulations allow observation of the evolution in kink site density, and are capable of resolving fundamental relationships in silicate mineral dissolution kinetics. As a first approximation, the results show that kink site density increases linearly with surface area. These results can then be interpreted in light of surface roughness parameters and their relationship to surface morphology and reactivity.