Theoretical study on structures and stability of SiCP2 isomers

The structures, energetics, spectral parameters and stability of the singlet SiCP2 isomers are explored at the density functional theory and ab initio levels. Eight isomers connected by ten interconversion transition states are located at the CCSD(T)/6-311G(2d)//B3LYP/6-311G(d)level. The kinetically stable isomers and their relevant interconversion transition states are further refined at CCSD(T)/6-311+G(2df)//QCISD/6-311G(d) level. At QCISD/6-311G(d) level, one four-membered ring isomer cSiPCP and two linear structures PSiCP, SiCPP possess considerable kinetic stability (more than 15 kcal/mol). The valence bond structures of three kinetically stable SiCP2 isomers are analyzed. The similarities and discrepancies in structure, energy and stability between SiCP2 and its analogous C2P2, Si2P2, SiCN2 and CSiNP molecules are also discussed. The predicted structures and spectroscopic properties are expected to be informative for the identification of the SiCP2 in the laboratory and space.