Raman band of matrix isolated NaMSeN clusters

Tungsten diselenide (WSe2) as a high capacity, low overpotential conversion electrode for sodium ion batteries

Tungsten diselenide (WSe₂) is demonstrated as an efficient electrode for sodium ion batteries for the first time.

Polyanionic Selenium Fragments and Vibrations in NaMSeNClusters

Density functional calculations on the series of clusters NaMSeNpredict different polyanionic selenium fragments depending on the relative amount of sodium. Calculations for Na2SeNclusters givee.g.horseshoe shaped polyanionic selenium chains that are accompanied by two Na atoms. The geometries obtained for NaMSe6clusters are changing from chains to Se2and Se3units 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−1is 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.