Photoelectron Spectroscopy and Theoretical Study of Cr <sub/><i>n</i> </sub> Si <sub/> 15– <i>n</i> </sub>^– ( <i>n</i> = 1–3): Effects of Doping Cr Atoms on the Structural and Magnetic Properties

摘要： CrnSi15?n? (n = 1?3) clusters were investigated by using size-selected anion photoelectron spectroscopy combined with density functional theory calculations. The results show that the most stable structure of CrSi14? is of C2v symmetry with the Cr atom encapsulated in a Si14 cage which can be viewed as a boat-shaped Si10 unit capped by four additional silicon atoms. A large HOMO?LUMO gap of neutral CrSi14 is confirmed based on the photoelectron spectrum of CrSi14?. Cr2Si13? has two isomers nearly degenerate in energy: one can be characterized as one Si atom interacting with a Cr2Si12 hexagonal prism while the other can be viewed as one Si atom capping a distorted Cr2Si12 hexagonal antiprism. Cr3Si12? has a D6d symmetric wheel structure in which three Cr atoms form an axle surrounded by 12 Si atoms. The magnetic moments of CrSi14?, Cr2Si13?, and Cr3Si12? increase from 1 to 3 μB and then to 7 μB with the increasing number of Cr atoms in the clusters. The magnetic moments of Cr2Si13? and Cr3Si12? are mainly contributed by the surface Cr atoms.