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: 1.98). 08/2012; DOI: 10.1007/s00894-012-1544-7
Source: PubMed

ABSTRACT 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.

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    ABSTRACT: The equilibrium geometries, growth patterns, stabilities, and electronic properties of bimetallic Be2Si n (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 Be2Si n clusters when n > 2. The calculated vertical ionization potential for the lowest-energy isomers are comparable to the experimental values of Si n+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 Si n 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 Be2Si n 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.
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