Abstract:

This article offers an overview of the recent progress in theoretical modelling of molecular reactions of atmospheric interest. The review covers processes in isolated molecules, e. g. vibrational overtone-induced processes in HNO(3) and H(2)SO(4). Another focal topic is thermally, as well as overtone-induced processes of NO(x), HNO(x) and other atmospherically relevant species in water clusters, the latter serving as models for water surfaces, aerosols and other water environments. Among the processes examined in water clusters are separations of NO(x) and HNO(x) into ion pairs in contact with water, and the reverse processes of anion/cation recombination to form neutral molecules. Physical insights into the mechanisms and properties of the processes, as extracted from theoretical simulations, are analysed. The methodology discussed in the review is mostly classical molecular dynamics simulations, using potentials directly from electronic structure methods. The merits and limitations of different electronic structure methods for the systems of interest are discussed. Limitations and open problems with regard to the classical dynamics approximation are also briefly examined. Concluding remarks are presented on the usefulness of classical dynamics with ab initio potentials for reactions of atmospheric chemistry. Possible directions for future progress are suggested.