Although there have been many advances in the development of quantum chemical methods and efficient algorithms, obtaining high-accuracy results on even small silver clusters continues to be a major challenge. Silver is, of course, not unique in this regard since the same can probably be said of clusters of all d-block elements. In addition, it is not uncommon for there to be a lack of consensus among experimental results or a lack of experimental data. Accordingly, predictive-quality theoretical data can play a crucial complementary role.  In this presentation, we report on our recent research on silver clusters. Our strategy is to use the coupled-cluster singles-and-doubles method combined with non-iterative triple excitations (i.e. CCSD(T)) with correlation-consistent basis sets and an effective core potential for the n = 1-3 shells. 4d and 5s electrons are correlated in all calculations. Effects of 4s and 4p correlation are also assessed. The success of our methodology was demonstrated through calculations on atomic and diatomic silver systems, for which well-established experimental data are available. These results suggest that our methodology can achieve predictive-quality data on larger systems. Properties of the larger systems obtained include structures and energies of ground and excited states, atomization energies, ionization energies, and electron detachment energies. For example, our study of Ag3 provided: (1) clear support for one of two reported ionization energies; and (2) an atomization energy that is near the middle of the experimental range. Overall the higher levels of theory used in the present research achieve consistent accuracy for a range of properties. Another benefit is that our results can provide useful reference points to assess results from density-functional theory (DFT) studies. We have observed that some prior DFT studies achieve adequate accuracy for some properties, but lack accuracy for others.

Systematic coupled-cluster calculations on silver clusters: Avoiding empirical corrections

248th National Meeting (2014)

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