Solvation of hydrogen halides on the surface of ice

Abstract

Heterogeneous processes on the surface of ice crystals in polar stratospheric clouds are thought to play a crucial role in the catalysis of reactions such as HCl + ClONO₂. An important consideration is the mechanism of solvation of the HCl molecules on the ice surface. A molecular dynamics simulation of the solvation of HCl, HF and HBr by an ice surface at 190 K is reported. The model allows for the solvation of the hydrogen halide by water molecules on the ice surface to form solvated ions. The simulations suggest that the ionic solvation process is energetically feasible for HCl and HBr, but not for HF.