超临界水中碳酸钾成核机理的分子动力学模拟

Nucleation Mechanism of K_2CO_3 in Supercritical Water Using Molecular Dynamics Simulation

针对超临界水对催化剂成核过程的影响机制问题,采用分子动力学模拟方法系统研究K2,CO3在不同温度和密度的超临界水中的成核过程.通过对体系的相互作用能、径向分布函数、配位数及体系氢键网络结构变化的分析,揭示了在K2,CO3成核过程中K+、CO32-与水分子间的相互作用机理.结果表明:在超临界态下,随着温度的升高、密度的降低,水溶液体系氢键结构破坏,水分子与K+和CO32-的作用急剧降低,K+和CO32-在静电作用下可冲破水分子的静电屏蔽,从而碰撞聚合形成离子对,继而进一步团聚成核;体系温度越高、密度越小,K2,CO3越易形成小而分散的团簇.

To better understand the effect of supercritical water（SCW） on the nucleation mechanism of K2CO3 cluster, the nucleation process of K2 CO3 in supercritical water under different temperatures and densities was investigated using molecular dynamics simulation. The interaction mechanisms between K^＋, CO3^2- and water during the process were revealed by analyzing the interaction energy, radial distribution function, coordination number and hydrogen bonding structure of the system. Under the supercritical condition, the hydrogen bonding structure of aqueous system is destroyed with temperature increasing and density decreasing. Therefore, the interaction of water with K^＋ and CO3^2- decreases rapidly. In this situation, K^＋ and CO3^2- can easily escape from the electrostatic shielding of water to collide and form ions-pair with electrostatic interaction, and then agglomerate into nuclei. The higher temperature and smaller density of the system will be more likely to lead to small and dispersive K2 CO3 clusters.