Theory and Simulation of Liquids, Solutions, and Nucleation Processes

熔体或溶液中的晶体成核是一个重要的过程，几乎在我们周围的环境中无处不在。冰晶在液态水中的成核，以及常见的盐如NaCl（岩盐）从溶液中的成核，都是这个提议中考虑的重要例子。水的正常凝固点是0 ℃，但纯水在凝固前可以过冷到接近-35 ℃。这意味着基本上所有地球上或大气中的冰成核都是通过与异物接触而促进的。这个过程被称为异质成核，异物被称为冰核。非均匀冰成核是大气中的一个重要过程，大气气溶胶的冰成核作用形成冰云，进而影响全球气候。虽然非均质冰核长期以来一直是一个研究课题，很少有人知道一个好的冰核的微观性质。这种知识的缺乏主要是因为与成核相关的小尺寸和快速时间不容易通过当前的实验获得。拟议中的研究将采用计算机模拟来研究这些问题。计算机模拟可以被看作是对真实的系统的代表性模型的“实验”，它使我们能够在分子水平上跟踪物理过程。这是一个非常强大的方法，它产生了对物理现象的微观理解，这是不可能的。我们将使用分子动力学模拟来研究特别重要的大气气溶胶，如粘土和其他矿物颗粒，以及获得更深入的了解影响非均质冰成核的一般因素。我们也将使用分子模拟来研究盐和其他分子固体从溶液中的结晶。其目的是再次探讨晶体诞生的基本机制，并确定晶体和溶液的性质，增强或抑制晶体成核和生长。** 许多物理和生物系统的状态和功能取决于与水（亲水性）和不与水（疏水性）有利相互作用的部分之间的平衡。同时具有亲水和疏水部分的分子称为两亲分子。我们将探讨如何竞争的亲水性和疏水性相互作用影响的纳米级结构的几个模型解决方案包含两亲性溶质。这项工作有望为为什么一些小分子作为蛋白质变性剂比其他小分子更有效地发挥作用提供新的见解。变性剂是使蛋白质在水溶液中将其结构改变为较不紧密（未折叠）状态的分子。**

Crystal nucleation from melts or solution is an important process that occurs practically everywhere in our surrounding environment. The nucleation of ice crystals in liquid water, and of common salts such as NaCl (rock salt) from solution are important examples considered in this proposal. The normal freezing point of water is 0 oC, but pure water can be supercooled to near -35 oC before freezing occurs. This means that essentially all ice nucleation on earth or in the atmosphere is facilitated by contact with a foreign body. This process is called heterogeneous nucleation, and the foreign body is termed an ice nucleus. Heterogeneous ice nucleation is an important process in the atmosphere because ice nucleation by atmospheric aerosols results in ice clouds, which in turn influence the global climate. Although heterogeneous ice nucleation has long been a subject of investigation, little is known about the microscopic nature of a good ice nucleus. This absence of knowledge is mainly because the small sizes and fast times relevant to nucleation are not easily accessible by current experiments. The proposed research will employ computer simulations to examine these questions. Computer simulations can be viewed as "experiments'' on representative models of real systems, which allow us to follow physical processes at the molecular level. This is a very powerful approach which yields a microscopic understanding of physical phenomena that is not otherwise available. We will use molecular dynamics simulations to examine particularly important atmospheric aerosols, such clays and other mineral particles, as well as to obtain a deeper understanding of the general factors that influence heterogeneous ice nucleation. We will also employ molecular simulation to investigate the crystallization of salts and other molecular solids from solution. The purpose is again to probe the underlying mechanisms of crystal birth, and identify the crystal and solution properties which enhance or inhibit crystal nucleation and growth. ******The state and function of many physical and biological systems depends on a balance between moieties that interact favourably with water (hydrophilic) and those that do not (hydrophobic). Molecules that have both hydrophilic and hydrophobic parts are called amphiphilic. We will explore how competing hydrophilic and hydrophobic interactions influences the nanoscale structure of several model solutions containing amphiphilic solutes. This work promises new insight into why some small molecules function more effectively than others as protein denaturants. Denaturants are molecules that cause proteins to change their structure to a less compact (unfolded) state in aqueous solution. **