Homolytic versus Heterolytic Dissociation of Alkalimetal Halides: The Effect of Microsolvation

Herein we report density functional calculations of homolytic and heterolytic dissociation energies of the diatomic alkalimetal halides MX (M = Li, Na, K, Rb, and Cs and X = F, Cl, Br, I, and At) and their corresponding microsolvated structures MX center dot(H2O)(n) (n = 1 to 4). Our results show that the homolytic dissociation energy of the MX center dot(H2O)(n) species increases with the number of water molecules involved in the microsolvated salts. On the other hand, the heterolytic dissociation energy follows exactly the opposite trend. As a result, while for the isolated diatomic alkalimetal halides, homolytic dissociation is always favored over heterolytic dissociation, the latter is preferred for CsF and CsCl already for n=2, and for n=4 it is the preferential mode of dissociation for more than half of the species studied.