ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The geometries and the bonding properties have been predicted for cyclic AlO2 and AlS2 species in doublet and quartet states using density functional theory, the second, third, and fourth orders Moller–Plesset theory, quadric configuration interaction singles and doubles including a perturbational estimate of the triples and coupled cluster singles and doubles including a perturbational estimate of the triples all-electron correlation methods with 6-311+G* and aug-cc-pvtz basis sets. The geometrical optimizations and the harmonic vibrational frequency analysis are performed using density functional theory and coupled cluster singles and doubles methods. The relevant energy quantities are also determined using several high-order electron correlation methods (the second, third, and fourth orders Moller–Plesset theory, quadric configuration interaction, and coupled cluster theories) at both basis set levels (6-311+G* and aug-cc-pvtz). For the doublet state, each species possesses a 2A2 ground state with a higher energy level 2A1 state. The corresponding state–state separations are 11 kcal/mol for AlO2 species and 7.2 kcal/mol for AlS2 species at coupled cluster singles and doubles including a perturbational estimate of the triples and 6-311+G* level. The calculations using quadric configuration interaction and coupled cluster singles and doubles including a perturbational estimate of the triples yield dissociation energies in three dissociation mechanisms of ∼59, ∼190, and ∼294 kcal/mol for AlO2(2A2), and of ∼64, ∼167, and ∼272 kcal/mol for AlS2(2A2), respectively, and other methods [B3LYP, B3P86, B3PW91, Moller–Plesset (n=2,3,4), quadric configuration interaction and coupled cluster singles and doubles] yield dissociation energies within ∼4.5 kcal/mol. For the quartet states, the 4B1 state is more stable than the 4B2 state with energy separations of 43.5 kcal/mol for AlO2 and 29 kcal/mol for AlS2. The 4B1 and 4B2 states are significantly higher in energy than the ground states by 28.9 kcal/mol (4B1) and 57.9 kcal/mol (4B2) for AlS2, and 24.2 kcal/mol (4B1), and 67.8 kcal/mol (4B2) for AlO2. Result analysis has indicated that the cyclic AlO2 in the 2A2 and 4B2 states should be classified as superoxides, but they have different spin density distribution. However, AlO2 in the 2A1 state should not be, while AlO2 in the 4B1 state may be classified as the dioxide. The AlS2 species in the 2A2 state should be classified as a supersulfide. Although the 2A1 state has some supersulfide character, it should not be classified as such. The AlS2 in the 4B2 and 4B1 states should be classified as the weak interaction molecular complex and the disulfides, respectively. However, these superoxides and supersulfides are far less ionic than the corresponding alkali metal superoxides. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1288386
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