Li Weiyu, Sun Zhaoru
School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Road, Shanghai 201210, China.
J Phys Chem Lett. 2025 Jan 16;16(2):503-509. doi: 10.1021/acs.jpclett.4c02771. Epub 2024 Dec 17.
Hydration in Mg solutions is critical in the chemical and biological industries. Researchers have identified a rigid first hydration shell, but the effects of ion-water and hydrogen bonding (HB) interactions beyond the first shell of Mg, especially when ion pairs form at high concentrations, remain controversial. On the basis of density functional theory, machine learning molecular dynamics was performed to study the second shell of Mg in MgCl solutions at various concentrations. At low concentrations, while both SCAN and PBE+TS-vdW predict a rigid first shell, SCAN affords a more softened structure due to its weakened HB interaction. The weakened HB interaction reveals the retarding effect of Mg on the water reorientation of the second shell. With an increasing concentration, SCAN reproduces the decreasing trend of the hydration number, which originates from Cl entering the second shell of Mg. Our results highlight the importance of accurately described ion-water interaction and HB interaction in the intermediate range.
镁溶液中的水合作用在化学和生物工业中至关重要。研究人员已经确定了一个刚性的第一水合层，但镁的第一水合层之外的离子-水和氢键（HB）相互作用的影响，特别是在高浓度下形成离子对时，仍然存在争议。基于密度泛函理论，进行了机器学习分子动力学研究，以研究不同浓度的MgCl溶液中镁的第二水合层。在低浓度下，虽然SCAN和PBE+TS-vdW都预测第一水合层是刚性的，但由于其较弱的HB相互作用，SCAN给出了一个更柔软的结构。减弱的HB相互作用揭示了镁对第二水合层水重排的阻碍作用。随着浓度的增加，SCAN再现了水合数的下降趋势，这源于Cl进入镁的第二水合层。我们的结果强调了在中间范围内准确描述离子-水相互作用和HB相互作用的重要性。
