title: Structural Evolution of Gold Clusters Aun-(n = 21-25) Revisited.
abstract: We performed a combined theoretical and experimental photoelectron spectroscopy study of the structural evolution of gold anion clusters Aun-in the size range n = 21-25, a special size range for gold anion clusters where extensive structural changes from the pyramidal structure at Au20-toward the core-shell structure at Au26-were expected to occur. Density functional theory calculations with inclusion of spin-orbit effects were employed to produce the simulated spectra for the selected low-energy isomers obtained from basin-hopping global minimum search. The comparison of these simulated spectra with reasonably well-resolved experimental photoelectron spectra resulted in the identification of the low-lying structures of the gold clusters. The fused-planar and hollow-tubular structures are found dominant in this special size range. The highly stable tetrahedral Au20unit (viewed as the fragment of face-centered cubic (FCC) bulk gold) was found intact only in the minor isomer at n = 21, whereas hollow-tubular structures were found prevalent in the n = 22-25 range. At n = 25, the dominant structure is a hollow-tubular one with two of gold pyramids fused together, but not a core-shell one as previously believed.
authors.affiliation: Department of Chemistry and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln , Lincoln, Nebraska 68588, United States.
authors.forename: Navneet Singh
authors.initials: NS
authors.lastname: Khetrapal
authors.affiliation: School of Basic Sciences, Discipline of Chemistry, Indian Institute of Technology Indore , Indore 452 017, Madhya Pradesh, India.
authors.forename: Satya S
authors.initials: SS
authors.lastname: Bulusu
authors.affiliation: Department of Chemistry and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln , Lincoln, Nebraska 68588, United States.
authors.forename: Xiao Cheng
authors.identifier: http://orcid.org/0000-0003-4672-8585
authors.initials: XC
authors.lastname: Zeng