The sign preference in sulfuric acid nucleation

The binding of sulfuric acid to a series of anions and cations of varying chemical complexity is studied using quantum chemical methods. Sulfuric acid is bound much more strongly to anions than cations, as expected from structural and general chemical considerations, and previous computational studies on charged sulfuric acid-water clusters. The results are likely to explain the sign effect observed in atmospheric nucleation phenomena, and indicate that the first steps of ion-induced nucleation are controlled by the specific chemical interactions between the core ion and the condensing molecules rather than by general physical (e.g. electrostatic) effects.