Structures and electronic properties of VSin- (n=14-20) clusters: a combined experimental and density functional theory study

We present a systematic study of the structures and electronic properties of vanadium-doped silicon cluster anions, VSin- (n = 14-20), by combining photoelectron spectroscopy (PES) measurements and density functional theory (DFT) based theoretical calculations. High resolution PES of low temperature (10 K) clusters are acquired at a photon wavelength of 248 nm. Low-lying structures of VSi14-20- are obtained by a genetic algorithm based global minimum search code combined with DFT calculations. Excellent agreement is found between the measured PES and the simulated electron density of states of the putative ground-state structures. We conclude that clusters with sizes n = 14 and n = 15 prefer cage-like structures, with the encapsulated vanadium atom bonding with all silicon atoms, while a fullerene-like motif is more favorable for n >= 16. For the sizes n = 16 to 19, the structures consist of a V@Si-14 with two, three, four, and five Si atoms on the surface of the cage. For n = 20 the structure consists of a V@Si-15 with five Si atoms on the surface of the cage. VSi14- has the highest stability and stands out as a simultaneous closing of electronic and geometrical shells.