Chemical Bond and Intermolecular Interactions

Abstract

In this review article, we analyze and compare chemical bonds and intermolecular interactions in several areas of their operation. In interactions of biologically important molecules we stress the importance of Coupled Cluster CCSD(T) benchmark data relevant to proper selection of DFT functionals for interactions in H-bonded and weakly bound systems with a balanced accuracy employing the benzene and uracil dimers as model systems. It is shown that in tetramers of cytosine and guanine the pair interactions greatly dominate over many-particle interactions which do not play any important role. We also describe interactions of coinage metals and gold nanoclusters with lone-pair ligands stressing the importance of relativistic effects leading eventually to a "relativistic bond". An efficient crosslinking of the polyethylene oligomers by gold atoms through C-Au-C bonds is suggested. We emphasize non-additivities in beryllium clusters: Pair interactions are of repulsive nature and many-particle interactions play the decisive role. CCSD(T) interaction energies in Be_n may serve as benchmarks for selecting proper DFT functionals.