Illuminating surface atoms in nanoclusters by differential X-ray absorption spectroscopy

Charles S. Spanjers, Thomas P. Senftle, Adri C.T. van Duin, Michael J. Janik, Anatoly I. Frenkel, Robert M. Rioux

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


We use differential extended X-ray absorption fine structure (Δ-EXAFS) to monitor the Ar-induced surface restructuring of silica-supported Pd nanoclusters (1 nm diameter) at 77 K. Δ-EXAFS analysis shows 9 ± 2 nearest-neighbor Pd-Pd bonds expand by 0.104 ± 0.005 Å as a result of Ar adsorption. Atomistic molecular dynamics simulations provide evidence for a model in which Ar drives restructuring of under-coordinated Pd atoms, leading to an increased Pd-Pd bond length of surface Pd atoms with no change in overall nearest-neighbor Pd-Pd coordination number. Based on observations from the atomistic simulations, it is likely that under-coordinated atoms are trapped in metastable states at 77 K and Ar provides the kinetic energy needed to overcome the barrier for surface restructuring. Together, experiment and theory highlight the ability of Δ-EXAFS to probe surface atoms of Pd nanoclusters.

Original languageEnglish (US)
Pages (from-to)26528-26538
Number of pages11
JournalPhysical Chemistry Chemical Physics
Issue number48
StatePublished - Nov 19 2014
Externally publishedYes


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