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

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的过程，例如生长，远离稳定平衡状态的平衡，并将这些方法应用于现实的材料问题。非平衡材料工艺在各种技术上重要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、薄膜传感器和防辐射材料的生长。该奖项为各种方法的开发提供支持，以延长时间和长度尺度，在此过程中，材料生长和缺陷形成可以在计算机上模拟，以及提高这种非平衡过程模拟的准确性。 PI将使用这些增强的方法来研究技术相关的过程，包括太阳能电池中使用的半导体薄膜的生长，金属多晶薄膜的生长，金属半导体生长中材料岛的成核，以及暴露于电子辐射引起的氮化硼纳米结构中缺陷的形成和损伤的修复。 在计算机上模拟非平衡过程的改进方法的发展，在扩展的长度和时间尺度上，可能会对各种材料相关过程的现实模拟产生重大影响。该项目有助于开发从原子到获得具有所需特性的材料的材料设计能力，并为材料基因组计划的成功做出贡献。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做出贡献。 该项目为具有广泛的国家、国际和社会影响的教育和外联活动提供了机会。 除了参与该项目的博士后研究助理和研究生外，还有几名本科生将通过物理和天文学系的本科生研究经验计划参与。 本科生也将在学年期间参加。 该奖项支持计算和理论研究，以开发方法来扩展温度加速动力学（TERMS）模拟的速度和准确性。 其中包括开发方法，以改善系统尺寸的温度加速动力学模拟的缩放，通过使用局部温度加速盆地搜索进行动态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的方法，以便使用大型数据库进行动态蒙特卡罗模拟，以及开发有效识别、表征和退出局部超级盆地的方法，以处理“小障碍”问题。这些方法将显着提高加速动力学模拟的速度和准确性，从而允许在扩展的时间和长度尺度上对复杂的有序和无序系统进行逼真的模拟。所开发的方法将用于研究与半导体技术和光电子学相关的各种不同的材料工艺。特别是，碲化镉薄膜生长的模拟将进行，以了解缺陷形成的动力学以及对生长条件的依赖。 为了研究多晶金属对半导体生长的早期阶段，还将模拟非晶硅上银中的岛形核和生长。 PI将使用模拟来研究掠射角沉积，目的是了解活化工艺对表面形态、晶粒尺寸、微观结构和缩放行为的影响（作为温度的函数）。 最后，为了探索氮化硼纳米结构材料在高温和危险环境中用作保护屏障的潜力，还将进行氮化硼纳米结构对电子辐照的响应的模拟。 这些模拟的结果将被用来理解缺陷的形成和演变的机制，以及解释一些明显的能量计算和实验之间的差异。 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做出贡献。 该项目为具有广泛的国家、国际和社会影响的教育和外联活动提供了机会。 除了参与该项目的博士后研究助理和研究生外，还有几名本科生将通过物理和天文学系的本科生研究经验计划参与。 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.