Theoretical study for the HNSi–HSiN isomerization: ab initio and DFT calculations

Ab initio and density functional theory (DFT) calculations using the GAUSSIAN 94 program have been performed to investigate the molecular structures of HNSi and HSiN in the ground state as well as the transition state for the HNSi–HSiN isomerization reaction at the 6-311G(d,p), 6-311+G(2d,p) and 6-311+G(2df,p) basis sets. The results show that DFT calculations at higher levels of theory reproduce experimental vibrational frequencies of both HNSi and HSiN better than ab initio methods including electron correlation effects. Those calculated geometries are accurate enough to predict the rotational constant of HNSi. The barrier height for the isomerization reaction is found to be about 10 kcal/mol.