Quasi-chemical study of Be${}^{2+}$(aq) speciation

Abstract

Be${}^{2+}$(aq) hydrolysis can to lead to the formation of multi-beryllium clusters, but the thermodynamics of this process has not been resolved theoretically. We study the hydration state of an isolated Be${}^{2+}$ ion using both the quasi-chemical theory of solutions and ab initio molecular dynamics. These studies confirm that Be${}^{2+}$(aq) is tetra-hydrated. The quasi-chemical approach is then applied to then the deprotonation of $Be(H_2O)_4^{2+}}$ to give $BeOH(H_2O)_3{}^{+}}$. The calculated pK${}_a$ of 3.8 is in good agreement with the experimentally suggested value around 3.5. The calculated energetics for the formation of BeOHBe${}^{3+}$ are then obtained in fair agreement with experiments.

11 pages, 3 figures