微电子机械系统的迅速发展对原子尺度下器件摩擦、润滑和磨损特性的研究提出了迫切要求，超滑机制的研究成为重要的科学问题。超滑是指摩擦系数小于0.001的润滑状态。原子尺度摩擦实验表明石墨具有超滑态。目前关于超滑发生机制研究的模型大都假设石墨无缺陷且是刚性的，如典型的Tomlinson模型。但石墨中的缺陷是必然存在的且运动可能具有局部性，实验观察到有刃型位错、晶界和位错网等。原子尺度摩擦是关于接触面的性质，因此位错等缺陷对晶体材料超滑态应该起着非常重要的作用。我们将基于晶体中的离散型广义Peierls-Nabarro模型建立石墨的离散模型，同时建立一个新的滑移模型，并结合string方法对具有缺陷的石墨滑动进行系统的数值模拟，给出这些缺陷在滑移过程中的运动规律，找出缺陷及其运动在滑动中的作用，对超滑机制的来源及规律进行有益的探索，为石墨超滑态在微电子机械系统中的应用提供理论指导。

With the rapid development of Micro-Electro-Mechanical-Systems (MEMS), understanding the atomic-scale friction, lubricity and wear is very important. Superlubricity becomes a basic scientific problem. Superlubricity is a phenomenon where the friction coefficient is less than 0.001. A lot of experiments give the evidence of superlubrecity in graphite. In the commonly used Tomlinson model for the superlubricity, the graphite is stiff and has no defect. In fact, there are defects in graphite and the sliding motion may have some local properties. In graphite, dislocation, grain boundary, and dislocation network have been found in many experiments. Atomic-scale friction is the properties of the contact interface. So we predict the defects should have great effect on the superlubricity. We will build a new discrete model for graphite based on the atomic generalized Peierls-Nabarro model. Based on the discrete model, we will build a new model for the sliding motion in graphite. We will treat some sliding modtion with high energy barrier as rare event and find the transition path, transition state, and energy barrier by string method. Base on the data gotten by our new models and methods, we would like to provide the details of the sliding motion in graphite with defects and their effects on the superlubricity mechanism, which will give theoretical basis for the application of graphite in MEMS.