The hydration rate, microstructure, mechanical properties and durability of Magnesium phosphate cement (MPC) prepared by different kinds of phosphates are quite different. These differences in macroscopic properties are essentially determined by microscopic chemical reactions. Therefore, in this paper, the adsorption mechanism of MgO interface to water and ions in the initial hydration process of MPC and the hydration structure of different ions were discussed at the molecular level. Herein, the structure and dynamics properties of water, NH₄⁺, Na⁺, K⁺ and Cl⁻ ions at MgO interface were analyzed by molecular dynamics method. The results show that the water molecules near the MgO interface can be connected to the matrix oxygen through hydrogen bonding and have a Coulomb interaction with the Mg on the interface. Therefore, the water molecules accumulate and stratify at the interface and the density distribution curve of water molecules forms a peak near the interface. This explains the stage of MgO adsorption of water molecules during the initial hydration of MPC. Besides, a large amount of ammonium ion, sodium ion and potassium ion are adsorbed on the MgO surface, and the cation density distribution curve also forms a peak near the interface. In addition, the radius of sodium ion is smaller and the Na-Os bond is stronger than that of NH4⁺ and K⁺ (Os represents the oxygen atom in MgO). Hence, the number of sodium ions adsorbed to the interface is the largest, the radial distribution function (RDF) of Na-Os forms a high-strength and sharp peak, The Os coordination number of Na⁺ is more than that of NH₄⁺ and K⁺. This also explains the experimental phenomenon that sodium magnesium phosphate cement has a faster hydration rate and shorter setting time than ammonium magnesium phosphate cement and potassium magnesium phosphate cement. Due to the adsorption of the interface, the mean square displacement of cations has decreased to some extent compared with that in the corresponding pure solution models. This study provides a basic understanding of the initial hydration mechanism of MPC at the molecular level.

不同种类的磷酸盐制备的磷酸镁水泥（MPC）的水合速率，微观结构，力学性能和耐久性差异很大。宏观性质上的这些差异基本上由微观化学反应确定。因此，本文从分子水平探讨了MPC初始水合过程中MgO界面对水和离子的吸附机理以及不同离子的水合结构。在此，水的结构和动力学性质，NH ₄ ⁺，钠⁺，K ⁺和Cl ^-用分子动力学方法分析了MgO界面的离子。结果表明，MgO界面附近的水分子可以通过氢键与基质氧相连，并且与界面上的Mg具有库仑相互作用。因此，水分子在界面处积聚和分层，并且水分子的密度分布曲线在界面附近形成峰。这解释了MPC初始水合过程中水分子的MgO吸附阶段。另外，大量的铵离子，钠离子和钾离子被吸附在MgO表面，并且阳离子密度分布曲线也在界面附近形成一个峰。此外，钠离子的半径较小，Na-Os键比NH4 ⁺和K ⁺的半径强（Os代表MgO中的氧原子）。因此，吸附在界面上的钠离子数量最多，Na-Os的径向分布函数（RDF）形成一个高强度且尖锐的峰，Na ⁺的Os配位数大于NH ₄ ^+的配位数。和K ⁺。这也解释了实验现象，即磷酸钠镁水泥的水化速率快，凝固时间短于磷酸铵镁水泥和磷酸钾镁水泥。由于界面的吸附，与相应的纯溶液模型相比，阳离子的均方位移有所降低。这项研究提供了分子水平上MPC初始水合机理的基本理解。