Collaborative Research: Accelerated Large-Scale Simulation Study of Atomic-Scale Wear Using Hyper-Quasicontinum

这项合作奖支持原子尺度上磨损机制的研究。一种新的预测计算方法--超拟连续(Hyper-QC)方法将被采用和推进。这种方法将使在真实滑动速度下的摩擦和磨损的计算模拟成为可能，关键事件和空间域的原子分辨率。模拟结果有望为原子尺度磨损的基本原理带来新的见解。这些知识是在宏观长度尺度上预测磨损的先决条件。因此，研究结果将为改进结构和材料工程以减少磨损提供有价值的见解。保守估计，传统机械部件的磨损造成的损失相当于一个工业化国家国内生产总值的1.5%左右。对美国来说，这相当于2013年的2500亿美元左右。在新兴的纳米技术领域，磨损引起的问题更加关键。磨损严重阻碍了带有可移动部件的系统的采用。因此，结果将使纳米技术的进一步进步成为可能。作为该项目成果而建立的所有计算机代码将通过专门的门户网站(qcmethod.org和Openkim.org)免费提供给研究界。该合作项目将为研究生提供培训。将与辛辛那提当地的高中一起组织一项科学和工程教育的外联计划，这些学校的学生主要来自代表性不足的群体。该项目的最终目的是开发一种新的纳米尺度磨损预测模型，用于在宏观长度尺度上减少磨损。研究方法是基于超QC方法的使用。为了能够对磨损进行分析，有必要进行方法创新，以推进超质量控制方法。这些进展将使该方法能够处理多个时间尺度。此外，还将建立一种考虑换热的原子区和连续区耦合的新方法。超质量控制方法将使考虑原子尺度磨损的关键实验成为可能。模拟将捕捉到使用原子力显微镜设备进行的磨损实验的所有相关特征。因此，原子分辨率保持在接触区，并考虑了与实际实验相当的滑动速度。磨损模拟将考虑各种具有技术意义的工程材料，包括硅、硅氧化物和类钻石碳。通过超QC模拟，将有可能确定纳米级磨损的原子尺度机制，并研究它们对重要实验条件的依赖，如滑动速度和温度。模拟结果与实验数据和观测结果之间的冲突将被用来改进现有的纳米级磨损模型。

This collaborative award supports research on the mechanics of wear mechanisms occurring at the atomic scale. A novel predictive computational approach, the hyper-quasicontinuum (hyper-qc) method, will be employed and advanced. This approach will enable the computational simulation of friction and wear at realistic sliding speeds with atomic resolution of critical events and spatial domains. The simulation results are expected to lead to new insights into the fundamentals of atomic-scale wear. Such knowledge is a prerequisite for predicting wear at macroscopic length scales. Hence the outcomes will provide valuable insight into the improved engineering of structures and materials with the aim of wear reduction. Wear of conventional mechanical parts has been conservatively estimated to cause a loss equivalent to approximately 1.5 percent of an industrialized nation's Gross Domestic Product. For the United States, this corresponds to about 250 billion dollars in 2013. The problems arising from wear are even more critical in the newly emerging field of nanotechnology. Wear significantly hampers the adoption of systems with moving parts. Thus, the outcomes would enable further advances in nanotechnology. All computer codes established as an outcome of this project will be made freely available to the research community via dedicated web portals (qcmethod.org and openkim.org). The collaborative project will provide training for graduate students. An outreach program for science and engineering education will be organized with local high schools in Cincinnati whose student populations are predominantly from underrepresented groups. The ultimate aim of this project is to develop a novel predictive model for nano-scale wear, which can be used to reduce wear at macroscopic length scales. The research approach is based on the use of the hyper-qc method. To enable the analysis of wear, methodological innovations to advance the hyper-qc method are necessary. These advances would enable the method to deal with multiple time-scales. A novel approach for coupling of atomistic and continuum regions accounting for heat transfer will also be established. The hyper-qc method will make it possible to consider key experiments on atomic-scale wear. Simulating will capture all relevant features of wear experiments with an atomic force microscope apparatus. Thereby, atomic resolution is retained in the contact region and sliding speeds comparable to actual experiments are considered. Wear simulations will consider various engineering materials of technological interest including silicon, silicon-oxides, and diamond-like carbons. From the hyper-qc simulations it will be possible to identify the atomic-scale mechanisms responsible for wear at the nano-scale and to study their dependence on important experimental conditions such as sliding velocity and temperature. Conflicts between simulation results and experimental data and observations will be used to improve existing models for nano-scale wear.