Effects of surface disorder on EXAFS modeling of metallic clusters

Small (1-5 nm) metal clusters may undergo significant surface relaxation under the influence of ligands, adsorbates, and substrate-induced stress. As a result, the nearest-neighbor distance between surface atoms can be reduced by up to 10% relative to those in the cluster core, enhancing the disorder in the interatomic distances. Accordingly, the pair distribution function extracted from EXAFS data under the standard assumption that the distribution function of nearest-neighbor bonds is quasi-Gaussian yields systematic errors. Here we analyze the surface disorder effects with emphasis on their impact on the accuracy of the size and shape determination of nanocatalysts.