Effect of an Electric Field on the Structure and Stability of Atmospheric Clusters

We study the influence of an applied electric field on the structure and stability of some common bimolecular clusters that are found in the atmosphere. These clusters play an important role in new particle formation (NPF). For low values of the electric field (i.e., |E| ≤ 0.01 V Å^-1), we demonstrate that the field response of the clusters can be predicted from simply calculating the dipole moment of the cluster and the dipole moments of the constituent molecules and that the influence on the association energy of the cluster is minimal (i.e., <0.5 kcal mol^-1). For higher field strengths |E| > 0.2 V Å^-1, there can be more dramatic effects on both structure and energetics, as the induced dipole, charge transfer, and geometric distortion play a larger role. Although such large fields are not very relevant in the atmosphere, they do exist in some situations of experimental interest, such as near interfaces and in intense laser fields.