Photoelectron spectroscopy and density functional calculations of CuSin- (n=4-18) clusters

We conducted a combined anion photoelectron spectroscopy and density functional theory study on the structural evolution of copper-doped silicon clusters, CuSin- (n = 4-18). Based on the comparison between the experiments and theoretical calculations, CuSi12- is suggested to be the smallest fully endohedral cluster. The low-lying isomers of CuSin- with n >= 12 are dominated by endohedral structures, those of CuSin- with n < 12 are dominated by exohedral structures. The most stable structure of CuSi12- is a double-chair endohedral structure with the copper atom sandwiched between two chair-style Si-6 rings or, in another word, encapsulated in a distorted Si-12 hexagonal prism cage. CuSi14- has an interesting C-3h symmetry structure, in which the Si-14 cage is composed by three four-membered rings and six five-membered rings. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3692685]