Quantum Models of Ion Solvation Thermodynamics

辛辛那提大学的托马斯贝克得到了化学系化学理论、模型和计算方法项目的一个奖项的支持，以开发新的计算方法来研究液体中的离子。 离子是带电的原子或分子物质，可以溶解在水或有机液体等溶剂中。 离子在非常广泛的自然和技术系统中非常重要。 食盐是日常生活中最常见的例子，但许多种类的离子在电化学、胶体、表面化学、大气化学、肥皂和洗涤剂、生物膜离子通道、地质学和储能设备（电池和超级电容器）中占有重要地位。 并非所有的离子都是一样的;事实上，离子特性（通过其大小、形状和化学性质）可显著影响给定系统的性质。 该项目的重点是更深入地了解是什么原因导致离子物种之间如此大的差异。 这项研究有助于开发更准确的模型，以了解离子如何与水或有机液体（如碳酸乙烯酯，每种电子设备中使用的锂离子电池中的溶剂）等溶剂相互作用。 为了达到这个目的，贝克和他的同事们采用了来自自然基础理论量子力学的精确模型。 他们的目标是了解离子溶剂化的基本方面，然后产生可靠的模型，可以帮助理解大气化学和更持久电池的开发等问题。 该项目的教育部分集中于继续发展可持续能源课程。 贝克教授目前是俄亥俄州超级计算机中心的州用户组主席，拥有1000多名活跃的计算科学用户。 本计画探讨离子在水及有机溶剂中溶解的基本问题。 离子溶剂化在表面化学、大气化学、肥皂和洗涤剂、生物膜离子通道、地质学和能量存储设备（电池和超级电容器）中占有重要地位。 贝克和他的同事们的目标是建立一个基本的单离子溶剂化的能量标度。 这为研究特定离子效应提供了更坚实的基础。 这项研究还导致了更好的经典模型的发展，这些模型可以应用于更大的系统，如海盐气溶胶和改进的电池。 界面附近离子的行为是所有这些问题的一个基本方面。 该研究有四个目标：研究水，有机溶剂和生物通道中的离子，并进一步开发一种新的随机算法，用于并行计算机上的量子模拟。 对水中离子的研究导致了对水的有效表面电位的准确预测，这是凝聚相化学中长期寻求的量。 这项工作采用从头计算量子模拟和准化学理论，以获得定量估计的散装和真实的水合自由能。 对有机溶剂中离子的研究将同样的想法应用于碳酸亚乙酯中的离子，碳酸亚乙酯是锂离子电池的关键电解质。 这项研究改进了这些系统的现有模型。 生物通道中离子的研究检查了细菌CLC通道蛋白中质子和氯离子的相互作用。 随机算法的发展可能为大规模量子模拟带来新的前瞻性算法。该方法采用随机微分方程求解单粒子密度矩阵。 除了科学的影响，研究广泛影响教育，通过发展可持续能源和领导的国家用户组在俄亥俄州超级计算机中心的课程，有超过1000名活跃的计算科学用户。

Thomas Beck of the University of Cincinnati is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop new computational methods to study ions in liquids. Ions are charged atomic or molecular species that can dissolve in solvents like water or organic liquids. Ions are important in a very broad range of natural and technological systems. Table salt is the most common everyday example, but ions of many kinds figure prominently in electrochemistry, colloids, surface chemistry, atmospheric chemistry, soaps and detergents, biological membrane ion channels, geology, and energy storage devices (batteries and supercapacitors). Not all ions are the same; in fact, the ion identity (through its size, shape, and chemistry) can dramatically affect the properties of a given system. The focus of this project is to gain a deeper understanding of what causes such large differences between ionic species. This research aids in developing more accurate models for how the ions interact with solvents such as water or organic liquids (such as ethylene carbonate, the solvent in the lithium (Li)-ion batteries used in every electronic device). Towards this end, Beck and his coworkers employ accurate models that come from the fundamental theory of nature, quantum mechanics. Their goal is to learn about basic aspects of ion solvation and then produce reliable models that can help understand problems like atmospheric chemistry and the development of longer-lasting batteries. The educational component of this project centers on continued development of a course on sustainable energy. Professor Beck is currently the chair of the State Users Group at the Ohio Supercomputer Center, with over 1000 active computational science users. This project addresses fundamental aspects of ion solvation in water and organic solvents. Ion solvation figures prominently in surface chemistry, atmospheric chemistry, soaps and detergents, biological membrane ion channels, geology, and energy storage devices (batteries and supercapacitors). Beck and his coworkers aim to establish a fundamental energy scale for single-ion solvation. This allows for a firmer groundwork for studying specific ion effects. The research also leads to the development of better classical models that can be applied to much larger systems such as sea salt aerosols and improved batteries. The behavior of ions near interfaces is an essential aspect of all of these problems. The research has four objectives: to study ions in water, in organic solvents, and in biological channels, and to further develop a new stochastic algorithm for quantum simulations on parallel computers. The study of ions in water leads to the accurate prediction of the effective surface potential of water, a long sought quantity in condensed phase chemistry. This work employs ab initio quantum simulations and quasi-chemical theory to obtain quantitative estimates of the bulk and real hydration free energies. The study of ions in organic solvents applies the same ideas to ions in ethylene carbonate, a key electrolyte in Li-ion batteries. That research improves current models for these systems. The study of ions in biological channels examines the interaction of protons and chloride ions in the bacterial CLC channel protein. The development of stochastic algorithims may lead to a new forward-looking algorithm for large-scale quantum simulations. The method employs stochastic differential equations to solve for the one-particle density matrix. Besides the scientific impacts, the research broadly impacts education through development of a course on sustainable energy and leadership of the State Users Group at the Ohio Supercomputer Center, with over 1000 active computational science users.