Los Alamos

The functionality of many materials of both fundamental and technological interest is often critically dependent on the nature andextentof any disorder that may be present. In addition, it is often difficult to understand the nature of disorder in quite well ordered systems. There is therefore an urgent need to develop better tools, both experimental and computational, for the study of such quasi-ordered systems. To this end, we have used neutron diffraction studies in an attempt to locate small metal clusters or molecules randomly distributed inside microporous catalytic materials. Specifically, we have used pair distribution function (PDF) analysis, as well as inelastic neutron scattering (INS) spectroscopy, to study interactions between adsorbate molecules and a microporous matrix. We have interfaced these experimental studies with computations of PDF analysis as well as modeling of the dynamics of adsorbates. These techniques will be invaluable in elucidating the local structure and function of many of these classes of materials. Background and Research Objectives It is widely recognized that the presence of defects in crystals and other solid materials can have a profound effect upon their chemical and physical properties, and consequently that defects have a major impact on the practical utility of many technological materials. The reason is that the functionality of a material is often critically dependent on the nature and extent of any disorder that maybe present, and it is often difficult to understand the nature of disorder in quite well ordered systems. There is also a great deal of current interest in complex, partially-ordered materials, such as the surfactant-mediated mesoporous silicas, biominerals, and hybrid organic-inorganic composites. Research on such materials has presented challenges that cannot easily be addressed by characterization *Principal Investigator, e-mail: juergen @lanl.gov