Bonding and correlation analysis of various Si 2 CO isomers on the potential energy surface

At various levels of theory, singlet and triplet potential energy surfaces (PESs) of Si 2 CO, which has been studied using matrix isolation infrared spectroscopy, are investigated in detail. A total of 30 isomers and 38 interconversion transition states are obtained at the B3LYP/6‐311G(d) level. At the higher CCSD(T)/6‐311+G(2d)//QCISD/6‐311G(2d)+ZPVE level, the global minimum 1 1 (0.0 kcal/mol) corresponds to a three‐membered ring singlet O‐cCSiSi ( 1 A′). On the singlet PES, the species 1 2 (0.2 kcal/mol) is a bent SiCSiO structure with a 1 A′ electronic state, followed by a three‐membered ring isomer Si‐cCSiO ( 1 A′) 1 3 (23.1 kcal/mol) and a linear SiCOSi 1 4 ( 1 Σ + ) (38.6 kcal/mol). The isomers 1 1, 1 2, 1 3 , and 1 4 possess not only high thermodynamic stabilities, but also high kinetic stabilities. On the triplet PES, two isomers 3 1 ( 3 B 2 ) (18.8 kcal/mol) and 3 7 ( 3 A″) (23.3 kcal/mol) also have high thermodynamic and kinetic stabilities. The bonding natures of the relevant species are analyzed. The similarities and differences between C 3 O, C 3 S, SiC 2 O, and SiC 2 S are discussed. The present results are also expected to be useful for understanding the initial growing step of the CO‐doped Si vaporization processes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009