Why study two-dimensional mixing?

Can you imagine not knowing what happens to the compounds in a mixture when that mixture is spilled on a table? Or what about contaminants are interacting at the surface of the ocean? It is well known that exciting chemical and physical properties emerge from the interactions between dissimilar components, and that It a mixture of compounds will alter the phase behavior of the participating components and result in new properties of the solution. However, chemical mixtures have generally been investigated in three-dimensions. While this is necessary to the understanding of our environment, it is not a complete picture because it ignores interfacial chemical processes. This incomplete picture presents a challenge for surface scientists: how do compounds mix on surfaces?, and can we predict the surface structure of a mixed adlayer? To answer these questions, it is vital to understand the mechanism behind two-dimensional mixing processes.