Thermodynamics and Structure of Chemically Heterogeneous Solid-Liquid Interfaces

布莱恩B。莱尔德的堪萨斯大学是由化学部的化学理论，模型和计算方法程序的理论和计算研究固液界面奖的支持。 这种界面在自然界和技术中很常见，从通常观察到的冰和水之间的界面到溶液中纳米颗粒的表面。了解这种界面的结构和热力学在包括化学、材料科学、纳米工程、冶金学、胶体科学和生物物理学在内的广泛领域中是重要的。例如，形成特定固液界面的能量成本控制液体是否完全覆盖（或润湿）固体表面，或者相反，珠化成液滴，就像刚打蜡的汽车上的水一样。然而，固液界面的直接实验研究是困难的-特别是对于高温和光谱探针缺乏透明度的金属系统，严重限制了实验研究。因此，计算方法在开发界面区域的详细原子级图像方面至关重要。在这项工作中，分子模拟技术被用来检查，在原子水平上，所谓的化学异质固-液界面的属性;即，界面中的固相和液相的化学组成显着不同。本研究中使用的特定系统是专门选择来解决界面科学中的基本问题，同时与特定的技术应用相关，例如了解纳米颗粒在溶液中的稳定性，金属脆化机制和蓝宝石纳米线的生长。该项目还有助于培训学生和博士后的计算化学，液态物理和材料科学的技术，并为他们提供了先进的科学编程的相当多的经验。这些技能在化学，工程，材料科学，制药科学，生物学和物理学的广泛应用中有着广泛的用途，并使它们在计算科学和技术的任何方面都具有相当大的市场潜力。这项研究的总体目标是了解，在一个基本的分子水平上，化学异构固液界面的热力学和结构特性是如何形成的原子和分子的相互作用和界面几何形状。 这项工作需要（a）开发、评估和应用新的计算方法和力场来研究凝聚相之间的界面，以及（B）将现有方法扩展到超出开发方法的系统类别。在这个项目中，开发了一个方法开发，分子动力学模拟和应用统计力学的协调程序，以进行化学非均匀固液界面的热力学和结构的系统研究。（a）化学性质不均匀的金属/金属固液界面，特别是研究铝和液体镓之间的界面，这是研究液体金属脆化的一个模型系统。(b)金属/金属氧化物固-液界面使用氧化铝（s）/Al（l）界面作为试验台-该系统提供了一个难得的机会来直接比较原子水平上固-液界面的实验和模拟结果。(c)曲面上的流体。本文研究了流体在波纹表面、凸胶体颗粒和凸表面上的界面自由能与曲率的关系。结果进行检查，以评估形态热力学，最近发展起来的曲面热力学理论的有效性。

Brian B. Laird of the University of Kansas is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division for the theoretical and computational study of solid-liquid interface. Such interfaces are common in nature and technology, from the commonly observed interface between ice and water to the surfaces of nanoparticles in solution. Understanding the structure and thermodynamics of such interfaces is important in a broad array of fields including chemistry, materials science, nano-engineering, metallurgy, colloidal science and biophysics. For example, the energy cost in forming a particular solid-liquid interface control whether the liquid completely covers (or wets) the solid surface or instead, beads up into droplets, like water on a freshly waxed car. Direct experimental study of solid-liquid interfaces, however, is difficult - especially for metallic systems where high temperatures and lack of transparency to spectroscopic probes severely limit experimental study. As a result, computational methods have been crucial in developing a detailed atomic-level picture of the interfacial region. In this work, molecular simulation techniques are used to examine, at an atomic level, the properties of so-called chemically heterogeneous solid-liquid interfaces; namely, interfaces in which the solid and liquid phases are significantly different in chemical composition. The particular systems used in this study were chosen specifically to address fundamental questions in interface science, while at the same time be relevant to specific technological applications, such as understanding the stability of nanoparticles in solution, mechanisms for metal embrittlement and the growth of sapphire nanowires. The project also contributes to the training of students and postdocs in the techniques of computational chemistry, liquid-state physics and materials science and affords them a considerable experience in advanced scientific programming. These skills have wide use in a vast array of applications in chemistry, engineering, materials science, pharmaceutical science, biology and physics and gives them considerable marketability in any aspect of computational science and technology. The overall goal of this proposed research is to understand, on a fundamental molecular level, how the thermodynamic and structural properties of chemically heterogeneous solid-liquid interfaces are shaped by atomic and molecular interactions and interfacial geometry. This effort requires both (a) the development, evaluation and application of new computational methods and force fields to study the interfaces between condensed phases and (b) the extension of existing methods to classes of systems beyond those for which the methods were developed. In this project, a concerted program of method development, molecular-dynamics simulations and applied statistical mechanics is developed to perform a systematic study of the thermodynamics and structure of chemically heterogeneous solid-liquid interfaces. The project focuses specifically on three classes of systems: (a) Chemically heterogeneous metal/metal solid-liquid interfaces, in particular a study of the interface between aluminum and liquid gallium, which is of interest as a model system for the study of liquid-metal embrittlement. (b) Metal/metal-oxide solid-liquid interfaces using the alumina(s)/Al(l) interface as a test-bed - a system which provides a rare opportunity to directly compare experiment and simulation results for a solid-liquid interface at the atomic level. (c) Fluids at curved surfaces. The curvature dependence of the interfacial free energy for a number of systems is investigated including fluids at corrugated surfaces, convex colloidal particles and convex surfaces. Results are examined to assess the validity of Morphometric Thermodynamics, a recently developed theory of curved surface thermodynamics.