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Theoretical investigation of the cyclic GaO 2 and GaS 2 molecules at DFT and correlated wave function levels
Author(s) -
Bu Yuxiang,
Chan Dezhan,
Song Xinyu
Publication year - 2000
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/1097-461x(2001)81:3<222::aid-qua5>3.0.co;2-h
Subject(s) - chemistry , bond dissociation energy , excited state , ground state , dissociation (chemistry) , coupled cluster , electronic correlation , density functional theory , computational chemistry , ionic bonding , basis set , molecule , atomic physics , ion , organic chemistry , physics
The geometries and the bonding properties have been predicted for cyclic GaO 2 and GaS 2 species at density functional theory (DFT), MP n ( n =2,3,4 with different substitutions), QCISD(T), and CCSD(T) all‐electron correlation levels with 6‐311+G* basis set. The geometrical optimizations and the harmonic vibrational frequency analysis are performed using DFT and second‐order Møller–Plesset (MP2) methods. The relevant energy quantities are also calibrated at the high‐order electron correlation levels [MP3, MP4, quadratic configuration interaction (QCI), and coupled cluster (CC)]. Each species possesses a 2 A 2 ground state with a higher energy level 2 A 1 state. The corresponding state–state separations are about 32 kcal/mol for GaO 2 species and about 20 kcal/mol for GaS 2 species at the QCISD(T)/6‐311+G* level. The QCISD(T) and CCSD(T) calculations yield dissociation energies of 42.0 and 59.0 kcal/mol for two species, respectively, and other methods yield dissociation energies within ∼5 kcal/mol. Result analysis has indicated that the cyclic GaO 2 should be classified as superoxide and the GaS 2 species should be classified as supersulfide in their ground state, and those in the excited state ( 2 A 1 ) should not be. However, the cyclic GaS 2 ( 2 A 2 ) is less ionic than the GaO 2 ( 2 A 2 ) and they are far less ionic than NaO 2 . © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 222–231, 2001