Investigation of OH radical in the water nanodroplet during vapor freezing process: An ab initio molecular dynamics study

چکیده مقاله

The hydroxyl radical (OH*) plays a crucial role in chemical processes of earth's atmosphere. Previous studies have focused on gas-phase OH* or OH* in aqueous solution. However, the vapor freezing process of water nanodroplet as a crucial part of cloud formation in the atmosphere is the subject of lively debate. The vapor freezing process was applied in this work in order to gain insight into the sustainability of the first solvation shell of OH* in water nanodroplet. In this study, we constructed three spherical systems consist of 191 H₂O molecules and one OH radical initially placed in different positions of the water nanodroplet. The vapor freezing of nanodroplet revealed the existence of hemibonded structure at low temperatures. Several hydrogen transfers occurred during increasing temperature. Moreover, the structural analysis indicated that in addition to hemibonded water molecule, the other two hydrogen-bonded water molecules located at the opposite sides of the hydroxyl oxygen have key roles in the stability of OH* during the freezing process. © 2021 Elsevier B.V.