Electronic states of the copper, silver, and gold silicides and their ions

The results of theoretical calculations for the ground state and low-lying excited states of SiCu, SiAg, and SiAu, and their ions SiCu+, SiAg+, SiAuand SiCu-, SiAg-, SiAu- are presented. Calculations were carried out with h igh-level correlated methods including relativistic corrections at the leve l of the Douglas-Kroll approximation. The ground state data are compared wi th the recent experimental findings and they differ in the assignment of th e ground-state symmetry. All neutral silicides are predicted to have the el ectronic ground state of (2)Pi symmetry, in agreement with earlier theoreti cal data. The neutral species and both negative and positive ions of silici des are found to be quite stable in the ground electronic state and in seve ral low-lying excited states. The relativistic effects bring significant co ntribution to the stabilization of the gold silicide and its ions in all el ectronic states investigated in this paper. (C) 2000 American Institute of Physics. [S0021-9606(00)30835-2].