Computer simulations of phase equilibria, dynamics, and solvation in ionic and polar fluids

流体是自然界中最常见的功能材料之一，是生物化学、化学工程、化学合成、软凝聚态物理和材料科学等许多学科的核心。流体中组成粒子之间的相互作用决定了它的热力学性质（如沸点）、动力学特性（如粘度、对交变电场的响应）以及它对其他粒子的溶剂化能力。在这项研究中，计算机模拟将用于探索分子和物质之间的密切联系。该项目将首先调查粒子之间的静电相互作用在决定物质是否具有沸点方面的作用，描绘气体和液体之间的边界。众所周知，带电粒子之间的库仑定律相互作用可以帮助物质形成不同的气体和液体状态，但尚不清楚电偶极子-偶极子相互作用是否也可以。将选择一种可以在离子和偶极极性之间变化的分子模型，并在计算机上模拟其凝聚能力，作为其离子性和偶极性的函数。这将使我们能够在离子流体或极性流体的微观特性与其总体行为之间建立详细的联系。该项目的下一阶段将关注离子在液体中的运动方式，以及由此产生的整体动力学特性，如粘度和扩散。离子的动力学性质决定了液体对交变电场的反应，这种反应有许多可能的应用，如微波加热和微波化学。我们的计算实验将对带电分子的平移和旋转方式产生独特的见解，从而影响电荷在液体中的传输。最后，离子流体和极性流体溶解其他较大颗粒的能力将被检验。这在大多数新化合物都是在溶液中合成的化学和蛋白质可能折叠以尽量减少与周围水接触的生物学中至关重要。这项研究的结果将推进我们对流体的基本认识，并可能在物理和生物科学的各个领域找到应用。

Fluids are amongst the most common and functional materials encountered in Nature, and are central to a large number of different disciplines including biochemistry, chemical engineering, chemical synthesis, soft condensed-matter physics, and materials science. The interactions between the constituent particles in a fluid dictate its thermodynamic properties (e.g. boiling point), its dynamical characteristics (e.g., viscosity, response to alternating electric fields), and its ability to solvate other particles. In this research, computer simulations will used to explore the intimate links between molecules and matter .The project will begin with an investigation of the roles of electrostatic interactions between particles in dictating whether a substance possesses a boiling point, delineating the boundary between gas and liquid. It is known that Coulomb's law interactions between charged particles can help a substance form distinct gas and liquid states, but it is not yet known whether electric dipole-dipole interactions can as well. A molecular model will be chosen that can be varied between the ionic and dipolar extremes, and its ability to condense will be simulated on a computer as a function of its ionicity and dipolarity . This will enable us to make a detailed link between the microscopic characteristics of an ionic or polar fluid, and its bulk behaviour.The next phase of the project will be concerned with the way ions move in a liquid, and the resulting bulk dynamical properties such as viscosity and diffusion. The dynamical properties of ions dictate how the liquid will respond to an alternating electric field, and this response has many possible applications, such as in microwave heating, and in microwave chemistry. Our computational experiments will yield a unique insight on the way charged molecules translate and rotate, and hence effect charge transport through the liquid.Finally, the abilities of ionic and polar fluids to dissolve other, larger particles will be examined. This is of utmost importance in chemistry where the majority of new compounds are synthesised in solution, and in biology where proteins may fold up to minimise their contact with surrounding water.The results of this research will advance our fundamental understanding of fluids, and may find application in diverse areas of physical and biological science.