Knowledge Bank

In order to aid the interpretation of experimental data obtained on small metal clusters, we have carried out calculations to determine the structure and vibrational frequencies which characterize the Group IB clusters $Cu3$, $Ag3$, and $Au3$. These calculations center on the application of the Diatomics in Molecules Approach to the description of clusters containing atoms with one unpaired valence electron in an s orbital. The group IB trimers are all found to have $C2v$ geometries ($\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}B2$ ground states) with bond angles ranging from 65 to $80\circ$. They should therefore have three Raman active vibrations. The vibrational potentials are found to be very anharmonic and $Ag3$ is characterized by two very low frequency modes $(\omega 3\sim 65$ $cm-1$, $\omega 2\sim 36$ $cm-1$). In addition the molecules also appear to be fluxional. The results obtained in this study are compared with recent matrix $Raman1$ and visible $excitation2$ profiles and a reinterpretations of the matrix Raman data is given.