Melanie Schnell, C. Herwig, J. A. Becker
September 25, 2009
Density functional calculations on the series of clusters Na M Se N predict different polyanionic selenium fragments depending on the relative amount of sodium. Calculations for Na 2 Se N clusters give e.g. horseshoe shaped polyanionic selenium chains that are accompanied by two Na atoms. The geometries obtained for Na M Se 6 clusters are changing from chains to Se 2 and Se 3 units highly dependent on the number of Na atoms. These clusters can be investigated experimentally by adding sodium atoms to selenium clusters in the reaction zone of a dual laser vaporization source and depositing them in a nitrogen matrix where they are investigated by Raman spectroscopy. An intense low frequency band between 165 and 225 cm −1 is observed that can be attributed by a simple model of dynamical charge to certain vibrational modes with considerable changes of Na–Se bond lengths. The model spectra allow a quite good description of the low frequency Raman band.