How ions affect the structure of water
How ions affect the structure of water
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DOI：
10.1021/ja026014h
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发表时间：
2002-10-16
影响因子：
15
通讯作者：
Dill, KA
中科院分区：
文献类型：
--
作者：
Hribar, B;Southall, NT;Dill, KA
我们在水中模拟离子溶剂化。我们使用水的MB模型，一个简单的二维统计力学模型，其中沃茨被表示为具有高斯氢键臂的Lennard-Jones盘。我们在MB沃茨中引入一个电荷偶极子。我们进行（NPT）蒙特卡罗模拟，探讨水分子如何组织周围的离子和周围的非极性溶质在盐溶液。该模型给出了很好的定性协议与实验，包括Jones-Dole粘度B系数，Samoilov和Hirata离子水合活化能，离子溶剂化热力学，和Setschenow系数Hofmeister系列离子，描述盐浓度依赖性的疏水溶质的溶解度。这里有两个主要观点：（1）电荷密度决定了离子与水的相互作用，（2）力的平衡决定了水的结构：静电（水的偶极子与离子相互作用）和氢键（水与邻近的沃茨相互作用）。小离子（kosmotropes）具有高电荷密度，因此它们导致附近沃茨的强静电有序化，破坏氢键。相比之下，大离子（离液剂）具有低电荷密度，并且周围的水分子主要是氢键。
We model ion solvation in water. We use the MB model of water, a simple two-dimensional statistical mechanical model in which waters are represented as Lennard-Jones disks having Gaussian hydrogen-bonding arms. We introduce a charge dipole into MB waters. We perform (NPT) Monte Carlo simulations to explore how water molecules are organized around ions and around nonpolar solutes in salt solutions. The model gives good qualitative agreement with experiments, including Jones-Dole viscosity B coefficients, Samoilov and Hirata ion hydration activation energies, ion solvation thermodynamics, and Setschenow coefficients for Hofmeister series ions, which describe the salt concentration dependence of the solubilities of hydrophobic solutes. The two main ideas captured here are (1) that charge densities govern the interactions of ions with water, and (2) that a balance of forces determines water structure: electrostatics (water's dipole interacting with ions) and hydrogen bonding (water interacting with neighboring waters). Small ions (kosmotropes) have high charge densities so they cause strong electrostatic ordering of nearby waters, breaking hydrogen bonds. In contrast, large ions (chaotropes) have low charge densities, and surrounding water molecules are largely hydrogen bonded.