A theoretical study of SiCN and SiNC in the Π electronic state based on global potential energy surfaces

Global potential energy surfaces (PESs) of SiCN/SiNC in the X ˜ 2 Π (A′ and A″) electronic state have been determined from MRCISD/aug-cc-pVTZ computations. Although spin–orbit coupling with lower-lying quartet states has a maximum of 3.4 cm−1 near linear SiCN, it is found to be negligible for bending form. Vibrational energies with J = 0 and 1 were computed up to 360 levels by quantum vibrational calculations using the three-dimensional PESs of the lowest 2A′ and 2A″ states. The Renner parameters for the linear SiCN and SiNC estimated from the lowest bending level are 0.300 and 0.283, respectively.