Use of the Metals Data File (CRYSTMET) in XAFS analysis

Abstract

The X-ray absorption spectrometry (XAS) technique has been widely used to determine the local structure of materials that are poorly suited to study by ordinary diffraction methods, such as fine particles or amorphous matter. XAS is among the major applications at synchrotron radiation facilities and many existing beamlines perform the measurement of XAFS (X-ray absorption fine structure) spectra. XAFS spectra can also be measured with conventional X-ray sources. Measurement of XAFS spectra is relatively straightforward, but real difficulties arise in the analysis and interpretation of the data. Contrary to single-crystal diffraction techniques, the structure is not obtained directly from the measured XAFS data. Model structures must be assumed and the corresponding simulated XAFS spectra must be calculated, with determination of which models best fit the measured data. Model building is a most important part of XAFS analysis, but creation of three-dimensional structures from crystal-chemical considerations can be a very time-consuming task. Utilization of a database of crystal structures and of its built-in structure analysis and display tools can considerably reduce the time and effort required by this task. As XAS is often used to study metals, a database of alloys and intermetallic compounds, such as CRYSTMET, incorporating an array of powerful tools, is then very useful.