The reaction mechanism of SiH₂ radical with HNCO has been investigated by a B3LYP method of density functional theory, while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311＋＋G** level. To obtain more precise energy result, stationary point energies were calculated at a QCISD (T)/6-311＋＋G**// B3LYP/6-311＋＋G** level. The intermediates and transition states were confirmed by the results of vibrational analysis and the Intrinsic Reaction Coordinates (IRC) calculation. The results indicate that the reaction of SiH₂ radical with HNCO has five channels, among which the reaction SiH₂＋HNCO→IM3→ TS4→IM5→TS5→IM6→SiH₂NH＋CO was the main pathway with the lowest activation energy.

Key words: silylene radical, isothiocyanic acid, reaction mechanism, activation energy, transition state