Theoretical study on the [Si, C, N, O] potential energy surface

The structures, energetics, spectroscopies, and stabilities of the doublet Si, C, N, O] radical are explored at the density functional theory and ab initio levels. Sixteen isomers are located, connected by 29 interconversion transition states. At the CCSD(T)/6-311+G(2df)//QCISD/6-311G(d)+ZPVE level, the lowest lying isomer is a linear SiNCO 1 (0.0 kcal/mol) mainly featuring a cumulene | . Si = N = C = O. The second and third low-lying isomers are bent OSiCN 2 (8.8) and bent OSiNC 3 (11.1), respectively. All the three low-lying isomers 1, 2, 3, and another high-lying species 5 (75.4) with a linear SiCNO structure are shown to have considerable kinetic stability and may be experimentally observable. The predicted results of isomers 1 and 2 are consistent with the previous mass spectrometry experiments. Moreover, the fourth low-lying species SiOCN 4 (23.9) with bent structure is expected to be observable in low-temperature environments. The bonding nature of the five isomers 1, 2, 3, 4, and 5 is analyzed. The calculated results are compared with those of the analogous molecules C(2)NO and Si(2)NO. Implications in interstellar space and N,O-doped SiC vaporization processes are also discussed.