First-principles insights into the structure and interaction mechanisms of hydrated Mg2+ clusters

Aqueous batteries attract attention due to their cost-effectiveness, high safety, and environmental friendliness. In aqueous systems, multivalent cations show higher capacity and energy density than monovalent ones. To gain insight into the initial hydration of Mg²⁺, we investigated Mg²⁺(H₂O)_n (n = 1–10) clusters using a comprehensive genetic algorithm and density functional theory. The results show that the Mg²⁺–water distance increases with n, the coordination number stabilizes at six, and additional water molecules have minimal impact. Binding-energy and charge analyses reveal a transition from strong ion–water interactions to hydrogen-bond stabilization. This work clarifies the atomic-scale hydration mechanism of Mg²⁺.