A Peierls Perspective on Mechanisms of Atomic Friction

本研究的目的是发展一个Peierls的观点，从时空演化的界面缺陷结构的原子摩擦机制。尽管定量的实验能力，检查纳米尺度的摩擦行为，现有的建模工作，如汤姆林森型模型或分子模拟，仍然无法定量解释的晶格不稳定性，速率和温度依赖性等的影响。一个Peierls型框架将建立取代奇异缺陷模型的界面上的非均匀滑移场。实验观察，如结构润滑性，摩擦各向异性，和接触尺寸的依赖性，可以解释为界面位错的启动和增殖及其与预先存在的界面缺陷的相互作用的结果。从动力学的角度来看，所提出的工作将检查的空间不均匀性的性质的速率决定过程，准确地计算激活能相对于界面缺陷，从而解释热激活摩擦行为的独特性，所提出的工作，相比，在这个领域的大量文献，是能够定量预测的原子过程中，管理的时空演变的界面缺陷在摩擦。这种观点使定量的实验比较，并解决现有的建模工作的缺点和困难。它将为本科生和研究生打开一扇大门，让他们参与多学科的教育/研究环境，从而推进和加强PI的重点研究和教育活动。的研究所。PI将开发新的教学材料和实际操作的计算演示，以纳入各种推广和多样性计划，从而促进高中和大学生对科学和工程职业的兴趣，以及公众意识的参与。

The objective of this research is to develop a Peierls perspective on the atomic-friction mechanisms from the spatiotemporal evolution of interface defect structures. Despite a quantitative experimental capability of examining nanoscale frictional behavior, existing modeling efforts, such as Tomlinson-type models or molecular simulations, are still unable to quantitatively explain the effects of lattice incommensurability, rate- and temperature-dependence, etc. A Peierls-type framework will be established to replace singular defect model by the inhomogeneous slip field on the interface. Experimental observations, such as structural lubricity, frictional anisotropy, and contact size dependence, can be explained as a consequence of initiation and multiplication of interface dislocations and their interactions with pre-existing interface defects. From the kinetics standpoint, the proposed work will examine the spatially inhomogeneous nature of the rate-determining process, accurately calculate the activation energy with respect to the interface defects, and thus explain the thermally activated frictional behavior.The uniqueness of the proposed work, as compared to a vast literature in this field, is the ability to quantitatively predict the atomic processes that govern the spatiotemporal evolution of the interface defects during friction. This viewpoint enables quantitative experimental comparisons and resolves drawbacks and difficulties of existing modeling efforts. It will open a broad door for both undergraduate and graduate students to participate in a multi-disciplinary education/research environment, and thus advances and enhances focused research and education activities in the PI?s institute. The PI will develop new instructional materials and hands-on computational demonstrations for incorporation into a variety of outreach and diversity programs, and thus promote the interests of high school and college students in science and engineering careers, as well as the engagement of public awareness.