Simulating Non-equilibrium Processes over Extended Time- and Length-Scales using Parallel Accelerated Dynamics

非技术总结该奖项支持计算和理论研究和教育，旨在开发新的方法，使用计算机来模拟材料中远离稳定平衡状态的过程，如生长，并将这些方法应用于现实材料问题。非平衡材料工艺在各种具有重要技术意义的材料和器件的生产中发挥着重要作用，包括半导体薄膜、太阳能电池、薄膜传感器和辐射防护材料的生长。该奖项为各种方法的开发提供支持，以延长在计算机上模拟材料生长和缺陷形成等过程的时间和长度尺度，并提高对此类非平衡过程模拟的准确性。该研究所将使用这些改进的方法来研究相关的技术过程，包括用于太阳能电池的半导体薄膜的生长、金属多晶薄膜的生长、金属中材料岛在半导体生长中的成核，以及由于暴露在电子辐射下的氮化硼纳米结构中缺陷的形成和修复。在扩展的长度和时间尺度上在计算机上模拟非平衡过程的改进方法的发展可能会对各种与材料相关的过程的现实模拟产生重大影响。该项目有助于发展从原子到获得所需性能的材料的设计能力，并有助于材料基因组计划的成功。在该项目过程中开发的软件将提供给更广泛的社区，为材料模拟社区的软件网络基础设施作出贡献。该项目为教育和外展活动提供了机会，具有广泛的国家、国际和社会影响。除了参与该项目的博士后研究助理和研究生外，还将有几名本科生通过物理和天文学系的本科生研究体验计划参与。本科生也将在学年期间参加。技术总结该奖项支持计算和理论研究，以开发扩展温度加速动力学(TAD)模拟的速度和精度的方法。其中包括：改进温度加速动力学模拟与系统规模的比例的方法的发展；通过使用局部温度加速盆地搜索进行动态动力学蒙特卡罗模拟的方法；在加速动力学模拟期间自动存储局部配置和过程以便利用大型数据库进行动力学蒙特卡罗模拟的方法；以及为了处理“小障碍”问题而有效识别、表征和退出局部超级盆地的方法的发展。这些方法将显着提高加速动力学模拟的速度和精度，从而允许在更长的时间和长度尺度上对复杂的有序和无序系统进行真实的模拟。开发的方法将用于研究与半导体技术和光伏相关的各种不同的材料工艺。特别是，为了了解缺陷形成的动力学以及对生长条件的依赖，将对碲化镉薄膜的生长进行模拟。为了研究多晶金属对半导体生长的早期阶段，还将对非晶硅上的银岛形核和生长进行模拟。PI将使用模拟来研究掠角沉积，目的是了解激活过程对表面形貌、晶粒度、微观结构和随温度变化的结垢行为的影响。最后，为了探索氮化硼纳米结构材料在高温和危险环境中作为防护屏障的潜力，还将对氮化硼纳米结构对电子辐照的响应进行模拟。这些模拟的结果将被用来理解缺陷形成和演化的机制，以及解释能量学计算和实验之间的一些明显差异。在该项目过程中开发的软件将提供给更广泛的社区，为材料模拟社区的软件网络基础设施作出贡献。该项目为教育和外展活动提供了机会，具有广泛的国家、国际和社会影响。除了参与该项目的博士后研究助理和研究生外，还将有几名本科生通过物理和天文学系的本科生研究体验计划参与。本科生也将在学年期间参加。

NONTECHNICAL SUMMARYThis award supports computational and theoretical research and education that is aimed to develop new ways to use computers to model processes in materials, such as growth, that operate far from the steady balanced state of equilibrium, and to apply these methods to realistic materials problems. Non-equilibrium materials processes play an important role in the production of a variety of technologically important materials and devices, including the growth of semiconductor thin films, solar cells, thin-film based sensors, and materials for protection from radiation. This award provides support for the development of various methods to extend the time- and length-scales over which process like materials growth and defect formation can be simulated on computers, as well as to increase the accuracy of simulations of such non-equilibrium processes. The PI will use these enhanced methods to study technologically relevant processes including the growth of semiconductor thin-films used in solar cells, metal polycrystalline thin-film growth, the nucleation of islands of materials in metal on semiconductor growth, and defect formation and healing of damage in boron nitride nanostructures arising from exposure to electron radiation. The development of improved methods for simulating non-equilibrium processes on computers over extended length- and time-scales is likely to have a significant impact on the realistic simulations of a broad variety of materials-related processes. This project contributes to developing a capability in the quest to design materials from the atoms up to obtain materials with desired properties, and contributes toward the success of the Materials Genome Initiative. Software developed in the course of this project will be made available to the broader community, contributing to the software cyberinfrastructure for the materials simulation community. This project provides opportunities for educational and outreach activities with broad national, international, and societal impact. In addition to the postdoctoral research associate and graduate students involved in this project, several undergraduates will participate through the Department of Physics and Astronomy's Research Experience for Undergraduates program. Undergraduate students will also participate during the academic year. TECHNICAL SUMMARYThis award supports computational and theoretical research to develop methods to extend the speed and accuracy of temperature-accelerated dynamics (TAD) simulations. These include the development of methods to improve the scaling of temperature-accelerated dynamics simulations with system size, a method to carry out on-the-fly kinetic Monte Carlo simulations by the use of local temperature-accelerated basin searches, a method to automatically store local configurations and processes during accelerated dynamics simulations in order to carry out kinetic Monte Carlo simulations with a large database, and the development of methods to efficiently identify, characterize, and exit local superbasins in order to deal with the 'small-barrier' problem. These methods will significantly enhance the speed and accuracy of accelerated dynamics simulations thus allowing realistic simulations of complex ordered and disordered systems over extended time- and length-scales. The developed methods will be used to study a variety of different materials processes which are relevant to semiconductor technology and photovoltaics. In particular, simulations of cadmium telluride thin-film growth will be carried out in order to understand the kinetics of defect formation as well as the dependence on growth conditions. In order to study the early stages of polycrystalline metal on semiconductor growth, simulations of island nucleation and growth in silver on amorphous silicon will also be carried out. The PI will use simulations to investigate glancing angle deposition with an aim to understand the effects of activated processes on surface morphology, grain size, microstructure and scaling behavior as a function of temperature. Finally, in order to explore the potential for boron nitride nanostructured materials to serve as protective shields at high temperatures and in hazardous environments, simulations of the response of boron nitride nanostructures to electron irradiation will also be carried out. The results of these simulations will be used to understand the mechanisms of defect formation and evolution as well as to explain a number of apparent discrepancies between energetics calculations and experiments. Software developed in the course of this project will be made available to the broader community, contributing to the software cyberinfrastructure for the materials simulation community. This project provides opportunities for educational and outreach activities with broad national, international, and societal impact. In addition to the postdoctoral research associate and graduate students involved in this project, several undergraduates will participate through the Department of Physics and Astronomy's Research Experience for Undergraduates program. Undergraduate students will also participate during the academic year.