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+, SiAu+ and SiCu-, SiAg-, SiAu- are presented. Calculations were carried out with high-level correlated methods including relativistic corrections at the level of the Douglas-Kroll approximation. The ground state data are compared with the recent experimental findings and they differ in the assignment of the ground-state symmetry. All neutral silicides are predicted to have the electronic ground state of (2)Pi symmetry, in agreement with earlier theoretical data. The neutral species and both negative and positive ions of silicides are found to be quite stable in the ground electronic state and in several low-lying excited states. The relativistic effects bring significant contribution to the stabilization of the gold silicide and its ions in all electronic states investigated in this paper. (C) 2000 American Institute of Physics. [S0021-9606(00)30835-2].