Heterogeneous catalysts are extremely important to the chemical industry. The goal of much current research is to develop predictive models for real world catalysts in order to optimize and exploit new processes. The first step in any predictive modeling is to understand the systems that are currently in use. A key question regarding these materials is the distribution of atoms within the catalyst particle, i.e., are the materials equally distributed within the particle or is there clustering or shelling of the constituents. This is a more general question than just catalytic systems and has applicability to many small cluster problems where normally immiscible systems can be forced to mix or order when confined to small volumes.

EXAFS analysis has provided useful information for these systems; due to the small scattering cross-section and large beam sizes of x-rays, the systems have only been studied as ensemble averages.