标题： 离子-水团簇、体相介质效应和离子水合 显示英文标题

标题： Ion-water clusters, bulk medium effects, and ion hydration

摘要： 气相离子-水团簇的热化学性质以及对团簇和水配体的水合自由能的估算用于计算离子的水合自由能。 通常，水合计算使用溶剂的连续体模型。 准化学理论的原始准化学近似提供了一个透明的框架来支撑这些努力。 在这里，我们评估原始准化学方法中的近似，并阐明介质的作用。 我们发现，介质可以稳定在气相中通常不观察到的团簇构型，同时降低离子的过量化学势。 这种效应在软离子中更为明显。 由于最小化离子过量化学势的配位数被确定为最优或最可能的配位数，对于这类软离子，如果不考虑介质对离子-水团聚反应的影响而得到的最优团簇尺寸和水合热力学性质可能与水溶液离子模拟中观察到的结果不同。 本文提出的思想预计将对将离子-水团簇的热化学转化为水合离子的热力学的实验研究具有相关性，并对结合高精度团簇计算与介质粗粒度模型的理论方法的发展具有意义。 显示英文摘要

摘要： Thermochemistry of gas-phase ion-water clusters together with estimates of the hydration free energy of the clusters and the water ligands are used to calculate the hydration free energy of the ion. Often the hydration calculations use a continuum model of the solvent. The primitive quasichemical approximation to the quasichemical theory provides a transparent framework to anchor such efforts. Here we evaluate the approximations inherent in the primitive quasichemical approach and elucidate the different roles of the bulk medium. We find that the bulk medium can stabilize configurations of the cluster that are usually not observed in the gas phase, while also simultaneously lowering the excess chemical potential of the ion. This effect is more pronounced for soft ions. Since the coordination number that minimizes the excess chemical potential of the ion is identified as the optimal or most probable coordination number, for such soft ions, the optimum cluster size and the hydration thermodynamics obtained without account of the bulk medium on the ion-water clustering reaction can be different from those observed in simulations of the aqueous ion. The ideas presented in this work are expected to be relevant to experimental studies that translate thermochemistry of ion-water clusters to the thermodynamics of the hydrated ion and to evolving theoretical approaches that combine high-level calculations on clusters with coarse-grained models of the medium.