Probing the structural and electronic properties of aluminum-sulfur Al n S m (2 ≤ n + m ≤ 6) clusters and their oxides

Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, 610065, China.
Journal of Molecular Modeling (Impact Factor: 1.74). 08/2012; 19(1). DOI: 10.1007/s00894-012-1544-7
Source: PubMed


Using the first-principle density functional calculations, the equilibrium geometries and electronic properties of anionic and neutral aluminum-sulfur Al( n )S( m ) (2 ≤ n + m ≤ 6) clusters have been systematically investigated at B3PW91 level. The optimized results indicate that the lowest-energy structures of the anionic and neutral Al( n )S( m ) clusters prefer the low spin multiplicities (singlet or doublet) except the Al(2)‾, Al(2), S(2), Al(4) and Al(2)S(4) clusters. A significant odd-even oscillation of the highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps for the Al( n )S( m )‾ clusters is observed. Electron detachment energies (both vertical and adiabatic) are discussed and compared with the photoelectron spectra observations. Furthermore, a good agreement between experimental and theoretical results gives confidence in the most stable clusters considered in the present study and validates the chosen computational method. In addition, the variation trend of chemical hardness is in keeping with that of HOMO-LUMO energy gaps for the Al( n )S( m ) clusters. Upon the interaction of oxygen with the stable AlS( m )‾ clusters, the dissociative chemisorptions are favorable in energy. The binding energy and Gibbs free energy change show completely opposite oscillating behaviors as the cluster size increases.

6 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: The equilibrium geometries, growth patterns, stabilities, and electronic properties of bimetallic Be2Sin (n = 1–11) clusters are systematically investigated at the B3LYP/6-311G(d) level of theory. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. The optimized results suggest that the three-dimensional structures are observed for the most stable isomers of Be2Sin clusters when n > 2. The calculated vertical ionization potential for the lowest-energy isomers are comparable to the experimental values of Sin+2 . According to the averaged binding energy, fragmentation energy, second-order energy difference and HOMO-LUMO gaps calculations, we identify that the Be2Si2 and Be2Si5 clusters are more stable, and Be atoms doping enhance the chemical reactivity of the Sin host. The natural population and natural electron configuration analyses indicate that the Be atoms possess positive charge at n = 1–5 but negative charge at n = 6–11. The chemical hardness of Be2Sin clusters show three local maxima at n = 2, 5, and 9, whereas three local minima are found for the corresponding chemical potential, meaning these clusters are more stable than their neighboring cluster sizes. Figure Be2Sin clusters
    Journal of Molecular Modeling 05/2014; 20(5):2242. DOI:10.1007/s00894-014-2242-4 · 1.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The structural and electronic properties of the neutral gallium sulfide (GaS2, Ga2S2, GaS4, and Ga2S4) clusters along with their anionic counterparts have been investigated systematically using the density functional theory, the second-order Møller–Plesset perturbation theory (MP2), and coupled cluster singles and doubles, including noniterative triples [CCSD(T)] with the 6-311+G(2df) basis set. At the CCSDT(T)//MP2 level, the lowest-energy configurations of the gallium sulfides prefer to be cyclic (GaS2), linear (GaS2−), kite shape with a thiozonide unit (GaS4 and GaS4−), rhombic (Ga2S2 and Ga2S2−), and planar with two sulfur atoms in a terminal position (Ga2S4 and Ga2S4−) geometries. In the gallium–sulfur binary clusters considered in this study, the neutral and anionic ground-state geometries prefer the planar structures with alternation of gallium and sulfur atoms. All the neutral clusters, with the exception of Ga2S2, possess high electron affinities, which range from 3.51 to 3.64 eV at the CCSDT(T)//MP2 level. A sequential addition of a sulfur atom to the Ga2Sn (n = 1–3) system increases the charge transfer from gallium atoms to sulfur atoms, the adiabatic electron affinity, and the HOMO–LUMO gap. The sufficiently large HOMO–LUMO gaps ensure the stability of these gallium sulfide clusters. The Ga2S4 → Ga2S2 + S2 process is the most thermodynamically favored toward dissociation. Graphical Abstract
    Structural Chemistry 06/2014; 25(3). DOI:10.1007/s11224-013-0316-z · 1.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The equilibrium geometries, stabilities and electronic properties of small PdnAlm (n+m≤6) clusters have been systematically investigated by density functional approach. The optimized geometries exhibit that the lowest-energy structures of PdnAlm clusters prefer a three-dimensional configuration, except for Pd2Al2, which prefers a two-dimensional structure. The binding energy (Eb), HOMO-LUMO energy gaps (Eg), vertical ionization potential (VIP), and vertical electron affinity (VEA) were calculated and discussed. The obtained results show that the bimetallic clusters are more stable than the monometallic clusters, indicating that the doping of Al atoms enhances the stability of pure Pdn clusters. Further, a closer inspection of the results showed that the stability of these clusters is directly related to the number of Pd–Al bonds in the cluster. It increases with increasing of the number of Pd–Al bonds. The calculated HOMO-LUMO energy gaps of PdnAlm clusters are in the range of 1.55–2.94 eV, indicating that these clusters are of semiconducting feature. The VIP varies from 5.94 to 7.06 eV, and the VEA ranges from 0.84 to 1.98 eV. Thus, the values of VIP are much higher than the VEA values, implying that the bimetallic clusters easily accept electrons.
    Physica B Condensed Matter 12/2014; 454:217–223. DOI:10.1016/j.physb.2014.08.004 · 1.32 Impact Factor
Show more