Near Neighbor Peak Shape Considerations in EXAFS Analysis

Abstract

The extended X-ray absorption fine structure, or EXAFS, has become recognized as a reliable source of information about the atomic scale structure of complex molecules, liquids, and solids. Under the proper circumstances, one can determine not only the position but also the type and number of the nearest neighbors of the excited atom. Analysis of EXAFS data is complicated, however, by our inability to extract the low k components of the structural information. Determining the proper shape for the nearest neighbor peak in the pair correlation function becomes an essential, and frequently non-trivial, aspect of the analysis. Its neglect can lead to errors in determining the coordination number and, to a lesser extent, the mean nearest neighbor distance, as has been pointed out by Eisenberger and Brown.1 On the other hand, using data on a superionic conductor, we demonstrate that EXAFS data of sufficient range and quality will enable a determination of the proper peak shape and, therefore, of the desired structural information. The incorporation of peak shape considerations into EXAFS analysis is discussed in general terms.