Investigating the photolysis of NO2 and influencing factors by using a DFT/TD-DFT method
2020
Wang, Xiaoxiang | Zhou, Lei | Liu, Yifan | Zhang, Kun | Xiu, Guangli
Photo-dissociation of NO₂ plays a very important role in atmospheric chemistry, e.g., it affects the O₃ level. In the present work, density-functional theory (DFT) and time-dependent density-functional theory (TD-DFT) were applied to investigate the detailed dissociation process of NO₂. Initially, ultraviolet–visible spectra were predicted by using TD-DFT at the 6-311G (d,p) level with different exchange correlation functionals. Among the functionals studied, CAM-B3LYP was found to show the best agreement with the experimental data. Exogenous energy is required for the initial step of NO₂ photo-dissociation, at which point a NO₂ molecule is excited to the excited state. Then, a N⋯O bond-breaking process occurs spontaneously. In addition, the potential impact of atmospheric constituents including water and a solid carbonaceous surface on such reaction were further evaluated. The presence of water molecules can increase the activation energy, resulting in a lower photolysis frequency, while a carbonaceous surface may exhibit nearly no effect on NO₂ photo-dissociation. The present study provides a novel strategy for furthering our understanding of the photochemical behavior of NO₂.
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