Theoretical study of small silicon clusters: Cyclic ground state structure of Si3

The ground state structure of Si3 is found to be cyclic (1A1, C2v symmetry) with an apex bond angle of ≂80°. The linear form, analogous to the known structure of C3, is found to be a saddle point which transforms without activation to the cyclic structure. There is a low-lying triplet state (3A′2, D3h symmetry) which lies only a few kcal/mol higher in energy. The nature of the bending potential surface of the ground state structure is also discussed.