Quantitative Understanding of Atomic Wear Using Accelerated Molecular Simulation

这项研究的目标是发展一个分子水平的理解和原子磨损的定量描述在单粗糙滑动。接触的移动表面会产生磨损，缩短设备寿命并降低能效。分子水平的模拟将被用来了解无定形二氧化硅尖端如何在低负载下在移动的相对表面上变钝。这种模拟设置类似于高密度热机械数据存储的聚合物表面上的硅尖端的扫描，在此期间，硅尖端的原生氧化层磨损。一种新的加速分子动力学算法将被用来加速滑动过程中罕见的碎片生成事件，从而接近实验的时间尺度。通过模拟不同速度、载荷、接触面积和温度下的尖端滑动，得到磨损率与载荷条件之间的定量关系。本研究将对Archard线性磨损定律和非线性键断裂模型在原子磨损机制中的适用性进行严格评估，这将丰富纳米尺度下磨损的基础知识，这对于设计具有移动接触的纳米器件（例如基于扫描探针的存储器存储、纳米光刻以及纳米机电系统）的操作条件指南和估计部件寿命至关重要。该计算平台也可用于研究未来的多微凸体磨损和摩擦化学效应。教育部分包括通过新视野：数学，工程，技术科学（METS）计划为对科学和工程感兴趣的高中生开展的推广活动; RPI材料建模课程的课程开发;为科学界不断努力改进开源可视化软件SimRePlay（www.simreplay.org）。

The goal of this proposed research is to develop a molecular-level understanding and a quantitative description of atomic wear during single-asperity sliding. Moving surfaces in contact can produce wear that shortens device lifetime and lowers energy efficiency. Molecular level simulations will be employed to understand how an amorphous silica tip blunts on a moving counter-surface under low loads. This simulation setup resembles the scanning of a silicon tip on polymer surfaces for high-density thermo-mechanical data storage, during which the native oxide layer of the silicon tip wears off. A novel accelerated molecular dynamics algorithm will be utilized to accelerate rare debris-generating events during sliding thus approach the experimental time scales. By simulating tip-sliding at various speeds, loads, contact areas and temperatures, the quantitative relation between the wear rate and loading conditions will be obtained. The applicability of the Archard's linear wear law and the nonlinear bond rupture model in the atomic wear regime will be critically evaluated.This research will enrich the fundamental knowledge on wear at the nanoscale, which is crucial for devising guidelines of operation conditions and estimating components lifetime for nanodevices with moving contacts, such as scanning probe-based memory storage, nanolithography as well as nano electromechanical systems. The computational platform developed here can also be used to investigate multi-asperity wear and tribochemical effects in the future. The educational components include outreach activities for high school students interested in science and engineering through the New Visions: Math, Engineering, Technology & Science (METS) program; curriculum development of a Modeling of Materials course at RPI; a continual effort on improving an open-source visualization software SimRePlay (www.simreplay.org) for the scientific community.