Speciation in Aqueous Zinc Chloride. An ab Initio Hybrid Microsolvation/Continuum Approach

The structure and energetics of zinc chlorides (ZnCl n 2- n, n = 0−4) in aqueous solution are studied by ab initio molecular orbital methods. The first solvation shell is included explicitly, the remainder of the solvent being modeled by the polarizable continuum method. The species Zn(H 2 O) 6 2+, ZnCl 2 (H 2 O) 2, ZnCl 3 (H 2 O) -, and ZnCl 4 2- are predicted to occur in an aqueous environment. The predictions are consistent with the limited structural and energetic data available. A comparison with the predictions of the continuum model alone shows the necessity of including the first solvation shell explicitly to model solvation energies, although the continuum model is successful in predicting structural changes of ZnCl + and ZnCl 2 upon hydration.