Structural Evolution and Bonding Properties of Cr 2 Si n - ( n = 1-12) Clusters: Mass-Selected Anion Photoelectron Spectroscopy and Theoretical Calculations.

We investigated the structural characteristics and bonding properties of Cr 2 Si n - ( n = 1-12) clusters by using anion photoelectron spectroscopy combined with density functional theory calculations. The experimental and theoretical results reveal that Cr atoms of the most stable structures of Cr 2 Si n - clusters with n < 8 are located at the surface, while the most stable structures of Cr 2 Si n - clusters with n ≥ 8 have one Cr encapsulated in the cage consisting of the other Cr atom and the Si atoms. The Cr-Cr interaction in the most stable structures of Cr 2 Si n - clusters is strong, except that the Cr-Cr interaction in the lowest lying isomer of the Cr 2 Si 5 - cluster is weak. The structure of Cr 2 Si 6 - can be viewed as the Cr 2 surrounded by a chair-shaped silicon six-membered ring with the C 2h symmetry. Cr 2 Si 12 - has a C 6v symmetric antihexagonal prism structure with two Cr atoms located at the center and the surface of the Si 12 cage, respectively. The magnetic moments of Cr 2 Si n - are 1 μB except that the magnetic moment of Cr 2 Si 5 - is 9 μB.