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 th e 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 u sed to estimate the particle size, a substantial influence of the particle shape was found to be present for the coordination numbers of higher neighb oring shells. Consequently, a method using the coordination number of the f irst 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 pres ented.