The Pronounced Effect of Microsolvation on Diatomic Alkali Halides: Ab Initio Modeling of MX(H2O)n (M = Li, Na; X = F, Cl; n = 1-3)

Abstract

Ab initio cluster calculations are reported in which the diatomic alkali halide (MX) species LiF, LiCl, NaF, and NaCl are microsolvated with up to three water molecules. Second-order Moller-Plesset perturbation theory (MP2) was used in conjuction with correlation consistent basis sets: cc-pVDZ (Li, Na) and aug-cc-pVDZ (F, Cl, O, H). Cyclic structures, with C[sub 1], C[sub 2], and C[sub 3] symmetries respectively, were found for the addition of one, two, and three water molecules. Harmonic frequencies were determined for the one and two water clusters in order to verify that these are true minima. For the one water cluster, a local minima of C[sub 2[nu]] symmetry was also characterized, as well as the transition state between the two equivalent cyclic structures. The incremental binding energies for the successive addition of water molecules tend to be comparable within each species and very similar between different species as well. The incremental binding energies (in kcal/mol) for each species were determined. 22 refs., 7 figs., 4 tabs.