气体的输运性质与分子间的碰撞过程有密切的关联，特别是碰撞截面对气体的自扩散、黏度和热导率有着重要的影响. 本文采用分子动力学模拟方法系统研究了常压下单原子气体He、Ar，双原子气体N2和多原子气体CH4的 自扩散系数及其温度依赖行为. 基于简单气体的经典散射模型并结合模拟结果探讨了气体分子自扩散碰撞截面与温度之间的关系. 本文结果对气体输运性质的教学与研究具有一定的指导意义.

The transport properties of gases are closely related to the collision process between molecules, and in particular, the cross sections significantly affect diffusion coefficient, viscosity and thermal conductivity. This work studies the diffusion coefficients of He, Ar, N2 and CH4 as well as their temperature dependence using molecular dynamics simulations. Based on the classical scattering model of simple gases combing with the simulation results, the temperature dependence of selfdiffusion cross section and its effect on diffusion coefficient are analyzed, which is helpful for the teaching and research of transport properties of gases in the course of college physics.