Estimation of mean size and shape of small metal particles by EXAFS

The possibility to estimate the mean size and shape of metal particles from their average coordination number, which is typically obtained from EXAFS (extended X-ray absorption fine structure) analysis, is evaluated. While the number of neighbors in the first and second coordination shell were found to be not significantly dependent on the particle shape, and thus can be used to estimate the particle size, a substantial influence of the particle shape was found to be present for the coordination numbers of higher neighboring shells. Consequently, a method using the coordination number of the first or second shell (N-1 or N-2) to estimate the average particle size and that of a higher shell (N-3 or N-4) to estimate the particle shape is presented.