温度梯度下石墨烯薄片定向运动的分子动力学模拟

Directed Motion of a Graphene Flake under Temperature Gradient:A Molecular Dynamics Study

固体在具有温度梯度的表面会从高温区向低温区定向迁移。为解明这种热驱运动的机理及影响因素,采用分子动力学模拟方法研究不同温度梯度下石墨烯薄片在单层石墨烯表面上的定向运动,分析石墨烯薄片在运动过程中的速度、能量变化。研究观察到,在不同温度梯度下石墨烯薄片的定向运动,即从石墨烯表面的热端运动到冷端,温度梯度越高,石墨烯薄片的运动距离越远,运动速度越快,且石墨烯薄片的运动速度与当前接触表面的温度相关。最后,从功和自由能的角度对这种热驱运动的机理进行分析。研究发现,系统对石墨烯薄片做正功,并且随着温度梯度的增大,石墨烯薄片所受力做的功越大;石墨烯薄片在运动过程中自由能不断减小,且向着系统能量低的方向运动。

The solid will migrate directionally from the high temperature area to the low temperature area on the surface with temperature gradient.In order to understand the mechanisms and influencing factors of this thermal driving movement,the movement of graphene flake on the surface of single-layer graphene under different temperature gradients is studied by molecular dynamics simulation,and the velocity and energy of graphene flake are analyzed.It is observed that the directional movement of graphene flake under different temperature gradients is from the hot end to the cold end of the graphene surface.The higher the temperature gradient is,the farther and faster the graphene flake moves,and the velocity of graphene flake is related to the temperature of the current contact surface.Finally,the mechanism of thermal driving is analyzed from the view point of work and free energy.It is found that the system does positive work on graphene flake,and as the temperature gradient increases,the work on graphene flake increases.The graphene flake moves towards the direction of low system energy and its free energy decreases continuously during the moving period.