An accurate relativistic effective core potential for excited states of Agatom: An application for studying the absorption spectra of Ag-n and Ag-n(+) clusters

A new 11-electron relativistic effective core potential (11e-RECP) for Ag a tom based on correlated level of theory and the associated atomic orbital ( AO) basis set have been derived which allows for an accurate determination of excited states. This has been verified by comparing the calculated excit ed states of the dimer with experimental data. Therefore, we applied the ne w 11e-RECP in the framework of the linear response equation-of-motion coupl ed-cluster (EOM-CC) method to determine absorption spectra of small Agn=2-4 and Ag-n=2-4(+) clusters. The correlation treatment of 11 electrons per at om and calculations of transition energies and oscillator strengths in a la rge energy interval allowed us to investigate the influence of d-electrons on the spectroscopic patterns. We have found that d-electrons play a crucia l role for accurate predictions of absorption spectra in spite of the fact that they are not always directly involved in the leading excitations contr ibuting to the intense transitions. The calculated spectroscopic patterns f or the stable structures are compared with available experimental data. (C) 1999 American Institute of Physics. [S0021-9606(99)30306-8].