Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 49: Nanomaterials II
MM 49.2: Vortrag
Donnerstag, 29. März 2012, 12:00–12:15, H 1029
Strengthening of Au-Au bonds in small gold clusters by adsorbing noble gases — •Luca M. Ghiringhelli, Sergey Levchenko, and Matthias Scheffler — Fritz Haber Institute, D-14195, Berlin
In state-of-the-art experiments for the vibrational spectra of metal clusters in the gas phase, photodissociation spectroscopy is performed on clusters complexed with noble gas (RG) atoms, where a RG atom is usually expected to form a weak van der Waals bond. By employing DFT (PBE functional with selected comparisons to PBE0, and to MP2 and CCSD(T) calculations), we surprisingly find a partially covalent bond of neutral dimers with RG. For RG = Ar, Kr, Xe one or two RG atoms can bind in a linear molecule with Au2. While both Hirschfeld and Mulliken analyses show a small electron transfer from the RG to Au2, the Au-Au bond shortens and the Au-Au stretch frequency increases. This is inconsistent with the expected effect of electron transfer to the antibonding orbital of the dimer. Electron-density (n) differences between the bonded systems and the isolated fragments show an accumulation of n between RG and the neighboring Au atom, and between the gold atoms. The analysis of the projected density of states reveals that, although only non-bonding orbital interactions and no charge transfer occurs between RG and Au2, the d-electrons of Au2 are redistributed due to the interaction with RG in such a way that the Au-Au σs bond is strengthened.