Potential energy surface study of [H, Si, C, N] and its ions

We performed a detailed theoretical study on the neutral, cationic and anionic [H, Si, C, N] potential energy surfaces (PESs) at the Gaussian-3//B3LYP/6-31G(d) level. The former four low-lying isomers HSiCN ¹1 (0.0 kcal/mol), HSiNC ¹2 (2.4), cCHNSi ¹7 (4.6) and HCNSi ¹3 (28.7) each have considerable kinetic stability, which supports their experimental characterization. In addition, two singlet isomers HNCSi ¹5 (29.7) and cNHCSi ¹8 (33.7), and four triplet isomers HSiCN ³1 (26.5), HSiNC ³2 (35.8), HCNSi ³3 (29.1) and HNCSi ³5 (29.7) are found to have high kinetic stability. They are expected to be detectable under suitable conditions. On the doublet [H, Si, C, N]⁺ PES, the linear structure HCNSi^{+ 2}3⁺ (0.0 kcal/mol) and HNCSi^{+ 2}5⁺ (8.6) are considerably more stable than HSiCN^{+ 2}1⁺ (37.2) and HSiNC^{+ 2}2⁺ (34.3), in contrast to the neutral [H, Si, C, N] PES. However, on the doublet anionic [H, Si, C, N]^- PES, the isomers HSiCN^{- 2}1^- (0.0 kcal/mol) and HSiNC^{- 2}2^- (10.4) are still the lower-lying isomers, similar to the neutral PES. Based on the [H, Si, C, N]^0,± PESs, the electron ionization and capture stabilities of various [H, Si, C, N] species are discussed, which might give insight into their mass spectrometric characterization in future. Finally, the proton ionization values of the two known interstellar radicals SiCN and SiNC are found to be very high, showing the high possibility of the existence of the cationic [H, Si, C, N]⁺ species.