Structural evolution and electronic properties of neutral and anionic TiASil (A = Sc, Ti; l ≤ 12): relatively stable TiASi4 as a structural unit

Simulated photoelectron spectroscopy was conducted to investigate the structural evolution and electronic properties of TiASil (A = Sc, Ti; l ≤ 12) clusters and their anions via the Perdew–Burke–Enzerhof scheme and extensive cluster search using the ABCluster software. The results revealed that the ground-state structures of the TiASil (A = Sc, Ti) clusters generally exhibited similar configurations except for the Ti2Si3, ScTiSi3, and TiScSi10 clusters. Furthermore, the TiASil clusters exhibited an adsorptive evolution pattern, and the TiASi4 unit was considered the basic constituent framework of the structure, excluding several distortions and minor changes. With the increase in the cluster size, the lowest-energy structures varied from the exohedral to the cage structures of the single-metal atom at the center. Regarding the second energy difference data, the neutral TiASi4 clusters exhibited better stability among the neutral and anionic TiASil (A = Sc, Ti; l ≤ 12) clusters. Furthermore, the chemical bonding in the TiASi4 clusters was analyzed by molecular orbitals (MOs), highest occupied MO–lowest unoccupied MO gaps, and adaptive natural density partitioning analyses for the best Ti2Si4 cluster especially, and the results were combined with the natural population analysis data. The hybridization of the spd orbital of the metal atoms, eight localized bonds, and four delocalized bonds may primarily account for the relative stabilities of the neutral, square bipyramidal structure of Ti2Si4. Thus, the TiASi4 clusters may be assembled as the basic units of silicon-based semiconductor clusters of large-size neutral and anionic TiASil.