The structural character of AlS2 species in quartet state: prediction at density functional theory and the correlated-wave function levels

The structural and the bonding properties have been predicted for AIS(2) sp ecies with C-2v symmetry in quartet state using density functional theory ( DFT), MPn (n = 2,3,4 with different substitutions) and CCSD(T) all-electron correlation methods with 6-311+G* basis set. The geometrical optimizations and the harmonic vibrational frequency analysis are performed using DFT an d CCSD methods. The relevant state-state energy separations and the dissoci ation energies are determined using several high-order electron correlation methods. Results indicates that for AIS(2) species in the quartet state, t here are a B-4(1) ground state and three higher-energy level low-lying exci ted states (two B-4(2) and one (4)A(1)). The cyclic AIS(2) in the B-4(2)(1) state should be classified as supersulfide, but with intermolecular weak-i nteraction or aluminide character, and is far less ionic than the correspon ding alkali metal superoxides and supersulfides. AIS(2) in the B-4(1) state should not be, while AIS, in the B-4(2)(2) state may be classified as the disulfide and that in (4)A(1) state should belong to aluminide. (C) 2001 El sevier Science B.V. All rights reserved.