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

Abstract

Simulated photoelectron spectroscopy was conducted to investigate the structural evolution and electronic properties of TiASi_l (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 TiASi_l (A = Sc, Ti) clusters generally exhibited similar configurations except for the Ti₂Si₃, ScTiSi₃, and TiScSi₁₀ clusters. Furthermore, the TiASi_l 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 TiASi_l (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 TiASi_l.