CDS&E: Molecular Dynamics Studies of the Structure, Dynamics, and Formation of Stable Glasses

非技术总结该奖项支持计算和理论研究，以促进对玻璃和玻璃材料的性能如何取决于它们的制造方式的理解。无定形的玻璃状固体材料已经成为日常生活的一部分。它们被用作手机的保护层和药物配方过程中的保护层。通过一种称为气相沉积的过程，可以在适当准备的衬底上制造玻璃形成材料。与从液体中冷却制备的玻璃相比，这一过程是一种产生具有所需性能的玻璃的方法，例如增加密度、增加机械稳定性和更高的抗化学反应能力。实验表明，分子在表面上移动的能力增强，使它们能够为蒸气沉积的玻璃找到比普通玻璃更有利的位置，并且进入的分子有助于将表面分子捕获到这些有利位置。此外，通过气相沉积过程获得的结构表现出与通过其他方法产生的玻璃不同的振动特性。PI和他们的团队将使用分子动力学模拟的能力来跟踪单个原子的位置，以研究气相沉积过程，并检查导致气相沉积玻璃与以恒定速度冷却产生的玻璃相比具有不同振动特性的微观结构。在该项目完成后，预计从计算机模拟中获得的见解将有助于指导研究人员试图制造具有理想特性的气相沉积玻璃，并将阐明玻璃微观结构的哪些方面导致这些理想特性。技术总结该奖项支持计算和理论研究，以研究气相沉积玻璃的形成和性质。在玻璃转变温度的85%左右的温度下，将玻璃形成材料气相沉积在衬底上，可以产生密度更高、热容更低、动力学和机械稳定性更高的玻璃，而不是通过传统的液体冷却方法形成的玻璃。实验表明，表面分子流动性的增加使分子能够找到较低的能量构型，而进入的物质会将分子捕获到这些较低的能量构型中。PI和他们的团队将使用分子动力学模拟来研究气相沉积过程和通过气相沉积形成的玻璃的结构特性，并将以这种方式形成的玻璃与以恒定速度冷却形成的玻璃进行比较。由于分子动力学模拟能够跟踪单个原子，该小组将研究蒸气沉积玻璃的动力学对衬底温度以及离衬底和自由表面的距离的依赖关系。此外，这项研究还将考察不同沉积速率下的气相沉积和不同冷却速率下冷却所产生的具有不同动力学和机械稳定性的玻璃的微观结构和振动态密度的差异。这项研究将有助于研究人员了解影响玻璃动力学和机械稳定性的因素，并帮助研究人员制造具有所需特性的气相沉积玻璃。

NONTECHNICAL SUMMARYThis award supports computational and theoretical research to advance understanding of how the properties of glasses and glassy materials depend on how they are made. Amorphous, glassy solid materials have become a part of everyday life. They are used as protective coatings for cell phones and in the drug formulation process. Through a process known as vapor deposition, glass forming materials can be made onto a properly prepared substrate. This process emerged as a method to create glasses with desirable properties, such as increased density, increased mechanical stability, and higher resistance to chemical reactions, as compared to glasses that are prepared by cooling from a liquid. Experiments suggest that the increased ability of molecules to move around on the surface enables them to find more favorable positions for the vapor deposited glass than for ordinary glasses, and that incoming molecules help trap the surface molecules into these favorable positions. Furthermore, the structures obtained by the vapor deposition process exhibit different vibrational properties than the glasses created by other means. The PIs and their team will use the ability of molecular dynamics simulations to track the positions of individual atoms to study the vapor deposition process and to examine the microscopic structures that give rise to the different vibrational properties of the vapor deposited glasses compared to glasses created by cooling at a constant rate. At the completion of the project, it is expected that the insights obtained from the computer simulations will help guide researchers trying to make vapor deposited glasses with desirable characteristics and will elucidate what aspects of a glass's microscopic structure lead to these desirable characteristics.TECHNICAL SUMMARYThis award supports computational and theoretical research to study the formation and properties of vapor deposited glasses. Vapor deposition of glass forming materials onto a substrate held at a temperature of around 85 percent of the glass transition temperature produces glasses that have higher densities, lower heat capacities, and higher kinetic, and mechanical stability than glasses formed by the conventional method of cooling from a liquid. Experiments suggest that increased mobility of the molecules at the surface allows the molecules to find lower energy configurations, and that incoming material traps the molecules into these lower energy configurations. The PIs and their team will use molecular dynamics simulations to study the vapor deposition process and the structural properties of glasses formed through vapor deposition, and compare glasses formed this way to those formed by cooling at a constant rate. Since molecular dynamics simulation are able to track individual atoms, the group will examine the dependence of the dynamics of the vapor deposited glasses on the substrate temperature and on the distance from the substrate and the free surface. Furthermore, the research will examine differences in the microscopic structure and the vibrational density of states of glasses with different kinetic and mechanical stability that are created by vapor deposition at different deposition rates, and by cooling at different cooling rates. This study will help researchers understand what influences the kinetic and mechanical stability of glasses, and aid researchers in making vapor deposited glasses with desired characteristics.