Structures, stabilities and electronic properties of TimSi−n (m = 1‒2, n = 14‒20) clusters: a combined ab initio and experimental study

Abstract

Titanium-doped silicon clusters anions, TimSi − (m = 1‒2, n = 14‒20), have been investigated by photoelectron spectroscopy and density functional theory (DFT) calculations. Low-energy structures of TimSi − clusters have been globally searched using a genetic algorithm combined with DFT calculations. The electronic density of states and vertical detachment energies have been computed at the HSE06/aug-cc-pVDZ level and compared to the experimental data. Excellent agreement is found between theory and experiment especially in case of the singly doped clusters. In general, clusters with size m + n ≤ 17 prefer cage structures, while larger sized clusters evolve on a quasi-fullerene Ti@Si14 structural motif. Natural population analysis reveals that the Ti atoms possess negative charges and thus act as electron acceptors. The calculated binding energies and HOMO–LUMO gaps show that the clusters with cage structures have significantly higher stability, particularly Ti1Si16− and Ti2Si15−. One reason is that neutral Ti2Si15 exhibits a closed-shell electronic structure as a superatom, like Ti1Si16.