Theoretical prediction of the structures and properties of cyclic AlS2 and GaS2 systems at density functional theory and all-electron correlation levels

摘要

The geometries and bonding properties have been predicted for cyclic AlS2 and GaS2 species at DFT, MPn (n = 2, 3, 4), QCISD(T) and CCSD(T) levels with the 6-311 + G (*) basis set. Harmonic vibrational frequencies were determined using DFT and MP? methods. The relevant energies were calibrated at high-order electron correlation levels. Each species possesses a (2)A(2) ground state with a higher-energy (2)A(1) state, lying 7.2 kcal/mol for AlS2 or 20.0 kcal/mol for GaS2 above at CCSD(T)/6-311 + G (*) level, and the corresponding CCSD(T) dissociation energies are 64.0 (AlS2: (2)A(2)) and 59.0 kcal/mol (GaS2: (2)A(2)), respectively. Analysis indicates that the cyclic AlS2 and GaS2 should be classified as supersulfide, but they are not as ionic as NaO2 and less ionic than AlO2. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 24]