Dear all,

 

I have some questions regarding crystallite size determination by EXAFS. I am investigating a system where there is a formation of metallic Cu in the system. I could see the presence of metallic Cu in the sample by XRD and EXAFS. However, high resolution TEM does not show any evidence of metallic Cu, perhaps the crystallite size is much smaller than the resolving power of the microscope and/or these crystallites are highly disordered.

 

Nevertheless, I thought of estimating the size of Cu crystallites by EXAFS. I know at least two approaches described by two prominent members of the mailing list, Scott Calvin and Anatoly Frenkel. The approach by Scott Calvin (http://link.aip.org/link/JAPIAU/v94/i1/p778/s1&Agg=doi) estimates crystallite size based on an assumption that they are spherical in shape. On the other hand, Anatoly Frenkel’s approach estimates both size and shape of crystallites based on the number of neighbors in each coordination shell obtained from EXAFS fit http://pubs.acs.org/doi/abs/10.1021/jp012769j

 

I have questions about the second approach. I would like to know how to calculate the number of neighbors in various coordination shells as a function of cluster size for different shapes ? Conversely, if one knows the number of neighbors in various shells from EXAFS fits, then how to correlate those numbers to clusters of different sizes and shapes as discussed by Anatoly Frenkel.

 

I know my questions are very specific, but I am sure many in the list would have already tried both these approaches and may provide some valuable insights.

 

Many thanks in advance !

 

With best regards,

Jatin