Published Research - Department of Chemistry


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Published in J. Chem. Phys. 132, 114306 (2010). Copyright © 2010 American Institute of Physics. Used by permission.


The effects of isoelectronic substitution on the electronic and structural properties of gold clusters are investigated in the critical size range of the two-dimensional (2D)-three-dimensional (3D) structural transition (MAun, n=8–11; M=Ag,Cu) using photoelectron spectroscopy and density functional calculations. Photoelectron spectra of MAun are found to be similar to those of the bare gold clusters Aun+1 , indicating that substitution of a Au atom by a Ag or Cu atom does not significantly alter the geometric and electronic structures of the clusters. The only exception occurs at n=10, where very different spectra are observed for MAu10 from Au11, suggesting a major structural change in the doped clusters. Our calculations confirm that MAu8 − possesses the same structure as Au9 with Ag or Cu simply replacing one Au atom in its C2v planar global minimum structure. Two close-lying substitution isomers are observed, one involves the replacement of a center Au atom and another one involves an edge site. For Au10 we identify three coexisting low-lying planar isomers along with the D3h global minimum. The coexistence of so many low-lying isomers for the small-sized gold cluster Au10 is quite unprecedented. Similar planar structures and isomeric forms are observed for the doped MAu9 clusters. Although the global minimum of Au11 is planar, our calculations suggest that only simulated spectra of 3D structures agree with the observed spectra for MAu10. For MAu11, only a 3D isomer is observed, in contrast to Au12 which is the critical size for the 2D-3D structural transition with both the 2D and 3D isomers coexisting. The current work shows that structural perturbations due to even isoelectronic substitution of a single Au atom shift the 2D to 3D structural transition of gold clusters to a smaller size.

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