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

Titanium-doped silicon clusters anions, Ti(m)Sin-(m = 1-2,n = 14-20), have been investigated by photoelectron spectroscopy and density functional theory (DFT) calculations. Low-energy structures of Ti(m)Sin-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 sizem + n <= 17 prefer cage structures, while larger sized clusters evolve on a quasi-fullerene Ti@Si(14)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 Ti(1)Si(16)(-)and Ti2Si15-. One reason is that neutral Ti(2)Si(15)exhibits a closed-shell electronic structure as a superatom, like Ti1Si16.