Fig.1. The decomposition process of CF3I.

3.2. Thermal decomposition mechanism of CF3I

The computational results of geometric optimization, frequency and energy analysis of the CF3I molecule as shown inFig.2. which suggest that the sum of electron and thermodynamic energy of the molecule corrected by ZPE is −347.737 Hartree, and there is no imaginary frequency in the molecule, indicating the reliability and stability of the investigated CF3I molecule. Besides, the bond angles of 2F─1C─5I and 4F─1C─5I in molecule have different bond lengths, suggesting the asymmetric structure of the molecule. And as listed in Table.1. The dissociation energy of 1C─5I (42.581 kcal·mol−1) bond is far lower than those of other chemical bonds in CF3I molecule, indicating that this chemical bond is relatively weak and easy to break, leading to the formation of CF3· radicals, which can interrupt the chain reaction of combustion and to achieve the purpose of fire-suppression. Furthermore, a comparison of the calculated bond energy of CF3I with that reported in the reference17 is presented in Table.S1 , implying the reliability of DFT computations in this work.