Theoretical study on the potential energy surface of SiC2O

The DFT/B3LYP/6-311G(d) and CCSD(T)/6-311G(2df) (single-point) methods have been used to investigate the potential energy surface of SiC₂O. A total of 11 isomers are located, which are connected by 13 interconversion transition states. The global minimum is the linear SiCCO with ¹Σ⁺ electronic state whose structure can be described as cumulenic double bonding form :SiCCÖ:. The isomer O-cSiCC possessing SiCC three-membered ring with an exocyclic OSi bond also shows considerable stability. Both SiCCO and O-cSiCC are kinetically stable towards isomerization and dissociation. Further calculations are performed at the CCSD(T)/6-311G(2df)//QCISD/6-311G(2d) level to obtain more reliable energies, geometrical parameters, harmonic vibrational frequencies and infrared intensities of the isomers. The energies and geometrical parameters are also calculated with the CASPT2//CASSCF methods.