基于密度泛函理论的第一性原理计算方法研究了纳米尺度下石墨烯层间摩擦现象，探讨了对称和非对称两种情况下双层石墨烯层间沿不同方向的摩擦性质．研究发现对于对称的双层石墨烯，层间摩擦沿不同方向同性；摩擦因数依赖于正压力，随正压力增大，摩擦因数的变化曲线分为三个阶段，在较小以及较大压力下，摩擦因数遵循Amonton法则不随压力变化而变化；而在中间3-6nN阶段，摩擦因数随压力增加线性增加．整个研究压力范围内摩擦因数在0．05-0．25之间．对于非对称性双层石墨烯层间摩擦，不同压力下摩擦因数在0．006上下波动，摩擦因数较两层对称性石墨烯大大降低．上述研究结果与实验一致．%Using the first-principles calculations within the density functional theory, we study the nanofriction between two graphene layers. The result shows that the friction of the graphene is isotropic, and the relationship between the load and the friction factor can be divided into three phases. For the smaller and larger loads, the friction factor does not increase as the load increases, which follows the Amonton＇s law; for the middle phase, with the increase of the load, the friction factor increases linearly. However, the nanofriction characteristics between the two incommensurate graphenes show that the incommensurate structure can reduce the friction factor between graphenes greatly, which is in agreement with experimental result. These studies provide a fundamental understanding about the nanofriction phenomenon between the graphene layers.
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