Anion photoelectron spectroscopy and density functional theory study of TM2Sin- (TM = V, Cr; n=14-20) clusters

We investigated the structural evolution and electronic properties of medium-sized silicon cluster anions doped with two transition metal atoms, TM2Sin- (TM = V, Cr; n = 14-20), by using mass-selective anion photoelectron spectroscopy combined with density functional theory (DFT) calculations. Putative ground state structures of these clusters were obtained by using a genetic algorithm coupled with the DFT calculations. It was found that the two TM atoms tend to form a TM-TM bond, which - except for V2Si19- - is shorter than the nearest neighbour distance in the crystalline state of the respective metals. The V2Sin- clusters with n = 14 to 17 exhibit structures based on a silicon hexagonal antiprism, while the larger ones exhibit more fullerene-like cage structures. Cr2Sin- clusters follow the same trend, although with a silicon hexagonal prism structure for n = 14 and 15, and the transition to fullerene-like structures occurring at n = 17. Among these clusters, TM2Si18- have the largest average binding energy and second order differences in energy, therefore the highest relative stability. All of the clusters possess total magnetic moment of 1 mu B, but with very different contributions from the doped TM atoms. Especially in the Cr doped clusters there is a tendency towards an anitiferromagnetic arrangement of the magnetic moments of the two Cr atoms.

Automated summary

We investigated the structural evolution and electronic properties of medium-sized silicon cluster anions doped with two transition metal atoms using mass-selective anion photoelectron spectroscopy combined with density functional theory calculations. The clusters exhibit different structures and magnetic properties, with the tendency of transition metal atoms to form bonds and contribute to the stability and magnetism of the clusters.