Extended Time Scale Simulation Studies of Nanoscale Friction

该奖项资助了应用原子尺度模拟来研究纳米尺度摩擦物理的新技术的发展。这些技术的目标是延长模拟的时间尺度，目前限制在不到一微秒。这使得目前的方法不适合模拟滑动速率远低于0.1 m/s的过程。为了比较，AFM实验和MEMs滑动在10-6 ？9米/秒。这些模拟方法也将扩展到固有非平衡模拟。预计这种长时间的非平衡模拟将有助于测试摩擦理论与模拟的单一粗糙接触的实际模拟。该项目的目标是扩大我们在纳米尺度上摩擦的基本物理和化学方面的知识。这些知识对于微型和纳米机电设备（MEMS/NEMS）的设计，解释原子力显微镜（AFM）表面表征的结果以及开发精密应用中有效的润滑方法至关重要。研究将能够分析摩擦响应在滑动速率和温度方面的转变。这些方法还将为研究吸附物（如碳氢化合物）的作用以及表面化学对摩擦和磨损的影响奠定基础，并有可能扩展到其他各种系统，包括断裂、疲劳、粘附和其他非平衡材料过程的研究。该项目将资助一名研究生和博士后研究员。研究员还将协调JHU MRSEC和PREM资助活动的外展活动，每年夏天将一名未被充分代表的少数民族学生带入实验室，以获得与PI和研究生密切合作的研究经验。

This award funds the development of new techniques for applying atomic scale simulation to study the physics of nanoscale friction. These techniques aim to extend the time scales accessible with simulation, which are currently limited to less than a microsecond. This renders current methods unsuitable for simulating processes that take place at sliding rates considerably slower than 0.1 m/s. For comparison, AFM experiments and MEMs sliding take place at sliding speeds of 10-6 ? 10-9 m/s. These simulation methods will also be extended to inherently non-equilibrium simulations. It is anticipated that such long-time non-equilibrium simulations will be useful for testing theories of friction against simulations in which a single-asperity contact is realistically modeled.The goal of this project is to expand our knowledge regarding the fundamental physics and chemistry of friction on the nanoscale. Such knowledge is critical for the design of micro- and nano- electromechanical devices (MEMS/NEMS), interpreting the results of atomic force microscopy (AFM) for surface characterization and developing effective methods for lubrication in precision applications. Investigations will enable the analysis of transitions in frictional response with respect to sliding rate and temperature. These methods will also lay the groundwork for investigations into the effect of adsorbates such as hydrocarbons and the influence of surface chemistry on friction and wear and have the potential to be extended to a variety of other systems including studies of fracture, fatigue, adhesion and other non-equilibrium materials processes. The project will support a graduate student and postdoctoral researcher. The investigator will also coordinate with the outreach activities the JHU MRSEC and PREM grant activities to bring an underrepresented minority student into the lab each summer to gain research experience working closely with the PI and graduate student.