Exploration of the atmospheric reactivity of N2O5 and HCl in small water clusters using electronic structure methods

Abstract

High level electronic structure calculations have been used to study the gas phase reactivity of N₂O₅ and HCl in small neutral water clusters containing one and two water molecules. The free energy barrier decreases from 61 (uncatalysed) to 39 kJ mol⁻¹ when catalysed by two water molecules where the reaction products involve ClNO₂ and HONO₂. A new pathway for the hydrolysis of N₂O₅ by a single water is identified with a barrier comparable to that for the uncatalysed reaction of N₂O₅ with HCl. The calculations predict these reactions may be important in contributing to the ozone destruction cycle. However, the calculations also suggest that heterogeneous catalysis will be favoured over the homogeneous process.