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

The structural and the bonding properties have been predicted for AlS2 species with C2v 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 and CCSD methods. The relevant state–state energy separations and the dissociation energies are determined using several high-order electron correlation methods. Results indicates that for AlS2 species in the quartet state, there are a 4B1 ground state and three higher-energy level low-lying excited states (two 4B2 and one 4A1). The cyclic AlS2 in the 4B2(1) state should be classified as supersulfide, but with intermolecular weak-interaction or aluminide character, and is far less ionic than the corresponding alkali metal superoxides and supersulfides. AlS2 in the 4B1 state should not be, while AlS2 in the 4B2(2) state may be classified as the disulfide and that in 4A1 state should belong to aluminide.