Probing the electronic structures and properties of neutral and anionic ScSi n (0,−1) (n = 1–6) clusters using ccCA-TM and G4 theory

Structural and Electronic Properties of LaSin-/0 (n = 2-6) Clusters: Anion Photoelectron Spectroscopy and Density Functional Calculations

The structures and electronic properties of LaSi_n^- (n = 2-6) anions and their neutral counterparts were investigated by anion photoelectron spectroscopy and theoretical calculations. The vertical detachment energies of the most stable structures of LaSi_n^- (n = 2-6) were measured to be 1.28, 1.58, 2.30, 2.05, and 2.91 eV, respectively. The lowest-energy isomer of LaSi₂^- is an isosceles triangle with a C_2v symmetry. For LaSi_3-6^- clusters, the most stable isomers are polyhedrons with La atom face-capping the Si_n frameworks. The lowest-energy structures of neutral LaSi_2,4,5 clusters are similar to their anionic counterparts. The most stable isomer of neutral LaSi₃ is a planar structure with C_2v symmetry, which is different from the triangular pyramid structure of LaSi₃^- anion. The lowest-energy isomer of LaSi₆^- is a C_5v symmetric pentagonal bipyramid structure, while for neutral LaSi₆ cluster, the C_5v structure is not the most stable one. The natural population analysis showed that there is electron transfer from La atoms to Si atoms in LaSi_n^-/0 (n = 2-6). The ZZ tensor component in isochemical shielding surfaces and the anisotropy of the induced current density analyses indicate that the most stable isomer of LaSi₆^- has aromaticity.

Quantum chemistry calculations of the growth patterns, simulated photoelectron spectra, and electronic properties of LaASil (A = Sc, Y, La; l ≤ 10) compounds and their anions

The growth patterns, simulated photoelectron spectra, and electronic properties of LaASi_l (A = Sc, Y, and La; l ≤ 10) compounds and their anions were studied via quantum chemistry calculations using the Perdew-Burke-Ernzerhof (PBE) method and unprejudiced structural searching software ABCluster. The results revealed that the growth patterns of the most stable structures of neutral and anionic LaASi_l showed an adsorptive mode. The lowest-energy structures (LESs) of the LaASi_l (l ≤ 7) clusters were similar, except for those of anionic LaYSi₄^- and LaYSi₅^- and neutral LaScSi₇. Additionally, we investigated and calculated the photoelectron spectra, vertical detachment energies, adiabatic electron affinities, relative stability, charge transfer, magnetic moment, and chemical bond analysis of the LaASi_l ground-state structures. The La₂Si_l clusters exhibited higher stability than the LaYSi_l and LaScSi_l systems owing to their higher dissociation energies (DEs). The DEs of the LESs in the LaASi₃ molecule are higher than those of other clusters. Thus, the LaASi₃ cluster shows potential as a building framework for Si-based cluster materials with good stability. The natural population analysis data and chemical bond analysis results showed that the spd hybridization of the orbitals of the metal atoms in the LaASi_l system occurred. Except for the LaScSi₉ and LaScSi₁₀ clusters, the neutral LaASi_l compounds transform into the corresponding anions when an extra electron is accepted by the Si clusters.

Bond dissociation energies of ScSi, YSi, LaSi, ScC, YC, LaC, CoC, and YCH

Predissociation thresholds of the ScSi, YSi, LaSi, ScC, YC, LaC, CoC, and YCH molecules have been measured using resonant two-photon ionization spectroscopy. It is argued that the dense manifold of electronic states present in these molecules causes prompt dissociation when the bond dissociation energy (BDE) is exceeded, allowing their respective predissociation thresholds to provide precise values of their bond energies. The BDEs were measured as 2.015(3) eV (ScSi), 2.450(2) eV (YSi), 2.891(5) eV (LaSi), 3.042(10) eV (ScC), 3.420(3) eV (YC), 4.718(4) eV (LaC), 3.899(13) eV (CoC), and 4.102(3) eV (Y-CH). Using thermochemical cycles, the enthalpies of formation, Δ_fH_0K°(g), were calculated as 627.4(9.0) kJ mol^-1 (ScSi), 633.1(9.0) kJ mol^-1 (YSi), 598.1(9.0) kJ mol^-1 (LaSi), 793.8(4.3) kJ mol^-1 (ScC), 805.0(4.2) kJ mol^-1 (YC), 687.3(4.2) kJ mol^-1 (LaC), 760.1(2.5) kJ mol^-1 (CoC), and 620.8(4.2) kJ mol^-1 (YCH). Using data for the BDEs of the corresponding cations allows ionization energies to be obtained through thermochemical cycles as 6.07(11) eV (ScSi), 6.15(13) eV (YSi), 5.60(10) eV (LaSi), 6.26(6) eV (ScC), 6.73(12) or 5.72(11) eV [YC, depending on the value of D₀(Y⁺-C) employed], and 5.88(35) eV (LaC). Additionally, a new value of D₀(Co⁺-C) = 4.045(13) eV was obtained based on the present work and the previously determined ionization energy of CoC. An ionization onset threshold allowed the measurement of the LaSi ionization energy as 5.607(10) eV, in excellent agreement with a prediction based on a thermochemical cycle. Chemical bonding trends are also discussed.