Electronic and Geometric Structural Properties of the Bare Ag₃ Cluster and Ions

The electronic and geometric structural properties of Ag₃, Ag₃^-, and Ag₃⁺ have been investigated by using an ab initio relativistic effective core potential within the framework of the self-consistent field and configuration interaction methods. For comparison purposes, parallel calculations were also carried out on the silver atom and diatom. Ag₃^- is found to be substantially bound (relative to Ag₃⁺ an electron) and linear in geometry. On the other hand, Ag₃⁺ is calculated to have an equilateral triangular geometry, and a significantly lower ionization potential is predicted for Ag₃ than for Ag2. The mirror-image, saw-tooth behavior of the electron affinities and ionization potentials of larger silver atom clusters with size, noted in the semiempirical molecular orbital calculations of Baetzold [J. Chem. Phys., 68, 555 (1978)], is also found here. The ground electronic state of Ag₃ (²B₁) is predicted to be slightly bent with a very shallow bending mode potential surface. At large bend angles (near equilateral triangle geometry), an ²A₁ state becomes the ground state, 0.14 eV above the ²B₁ state. The ²A₁ and ²B₁, states are two branches of a Jahn-Teller split degenerate ²E’ state at D2h symmetry. The energy proximity of these two states could lead to the geometrical isomerization effects proposed by Ozin et al [Inorg. Chem., 18, 2932 (1979)] on the basis of low-temperature, rare-gas matrix isolation spectra of Ag₃. The general topological features of the ground-state potential surfaces of Ag₃ and Na3 [R. L. Martin and E. R. Davidson, Mol. Phys., 35, 1713 (1978)] are very similar.