Anomalous Water\nPenetration in Al<sup>3+</sup> Dissolution

The physicochemical characterization of trivalent ions\nis limited\ndue to a lack of accurate force fields. By leveraging the latest machine\nlearning force field to model aqueous AlCl<sub>3</sub>, we discover\nthat upon dissolution of Al<sup>3+</sup>, water molecules beyond the\nsecond hydration shell are involved in the hydration process. A combination\nof scissoring of coordinating water is followed by synchronized secondary\nmotion of water in the second solvation shell due to hydrogen bonding.\nConsequently, the water beyond the second solvation penetrates through\nthe second solvation shell and coordinates to the Al<sup>3+</sup>.\nOur study reveals a novel microscopic understanding of solvation dynamics\nfor the trivalent ion.