Synchrotron x-ray scattering studies of earth materials

During the past decade, the increased availability of synchrotron x-ray sources combined with new analysis techniques have revolutionized x-ray scattering methods. These methods provide the primary means for structural characterization of materials of all types. For example, powder diffraction techniques are no longer restricted to phase identification and unit cell definition, but now can be used to refine the crystal structure of a powdered phase using the full pattern-fitting method devised by Rietveld. In addition, intensity information obtained from powder diffraction experiments can be used to solve crystal structures with Patterson techniques or direct methods of structure solution. The use of synchrotron radiation in powder diffraction experiments had led to dramatic improvements in resolution, peak shapes, and time required for data collection, making such structure solution work on powder samples feasible. An example of the improved resolution possible with synchrotron-based diffraction on a powdered mixture of the minerals quartz (SiO2), orthoclase (KAlSi3O8), and albite (NaAlSi3O8) is reviewed. Although it is possible to identify phases in the laboratory-derived pattern, it is not possible to extract separate peak integrated intensities for Rietveld analysis. The synchrotron-derived pattern overcomes this difficulty