Study on Dissociation Properties and Spectra of Halon 1301 in External Electric Field.

Halon-1301 (CF3Br) can make Br radicals with UV radiation, which poses a great threat to the ozone layer in the atmosphere. Necessary methods should be taken for the degradation of the exhausts of Halon-1301. In this paper, density functional (DFT) theory at B3LYP/6-311G++(d,p) level are employed for the study of dissociation properties and spectra of Halon-1301 in external electric field, including bond length, total energy, HOMO-LUMO energy gap, infrared spectra and dissociation potential energy surface (PES). The obtained results show that, with gradually increasing the external field from 0 to 0.03 a.u. along the molecular axis Z (C—Br bond direction), the total energy decreases, while the dipole moment decreases at the beginning and then increases. With the climbing of the field, HOMO-LUMO energy gap increases, and C—Br bond length increases while C—F bond length decreases. The variations of vibrational frequency and intensity of molecular IR spectra in external electric field are also investigated. Further studies show that with increasing the external electric field from 0 to 0.03 a.u., the dissociation PES along C—Br bond becomes unbound with disappearing of the barrier for the dissociation. The external electric field of 0.03 a.u. is sufficient to induce the degradation of CF3Br with C—Br bond breaking. Such results provide an important reference for the degradation of Halons via the external electric field.