OH + HCl Reaction on the Surface of Ice: An Ab Initio Molecular Dynamics Study

Abstract

We have investigated the OH + HCl reaction on the surface of ice using Born−Oppenheimer molecular dynamics (BOMD) simulation. The present work revealed that the OH + HCl reaction becomes ∼1 order of magnitude faster on the ice surface compared to the bare reaction. The BOMD simulation also indicates that the Cl radical formed on the ice surface through the title reaction can form two hydrogen bonds at a time with the water molecules present on the ice surface; hence, the Cl radical cannot escape from the ice surface easily.

Can Ozone Dissociate at the Surface of Water (Water Droplet and Ice) without Light?

“…For the water droplet, we have run the simulation at 250 and 300 K, whereas, for the ice surface, simulation was run at 190 and 220 K. The simulation was performed using an integration step of 0.5 fs for a total time of 1 ps for the ice surface and 1.5 ps for water droplets. Further, we have used 191 water molecules to model the water droplet, and 270 water molecule to model the ice surface − (for detail of modeling the water droplet and ice surface, see section 1 of the Supporting Information).…”

Dissociation of H2O2 on water surfaces (ice and water droplets)

“…Interestingly, in a recent study, we have shown that OH radicals can also be formed from the thermal dissociation of ozone molecules on water surfaces. 21 In that study, we have shown that ozone can give an OH radical in two steps; first, the peroxy linkage (O-O bond) of the ozone molecule breaks on the water surface to form O 2 and an O atom, and in the second step, the O atom reacts with a surface water molecule to form an OH radical. Interestingly, H 2 O 2 also has a peroxy linkage, and hence, it is possible that, similar to ozone, it can also dissociate on the water surface to form OH radicals.…”

“…14,15 In addition, H 2 O 2 can also react with the halides present on the ice surface to form a gaseous halogen that can affect the ozone present in the atmosphere. 16,17 Although the chemistry of the OH radical is one of the most studied subjects, there are discrepancies between the predicted atmospheric models and the experimentally observed value of the concentration of OH radicals. [18][19][20] It suggests that some paths for the formation of OH radicals in the atmosphere are still missing.…”

Effect of (H2O)n (n = 1 and 2) on HOCl + Cl reaction

“…[13][14][15][16][17][18][19] There is vast literature available that suggests that water is an effective catalyst for HAT reactions. 6,[20][21][22][23][24][25][26][27][28][29][30][31] For example, it was found that the OH + HCl reaction becomes essentially a barrierless reaction in the presence of a water molecule. 24 In another example, it was found that the CH 3 O + O 2 reaction barrier reduces from 3.01 kcal mol À1 to À1.86 kcal mol À1 in the presence of a water molecule.…”