超薄氩膜热传导的分子动力学模拟

采用基于经典理论的平衡态分子动力学(EMD))方法，在无量子化修正的条件下，计算了固态氩(Ar)在低于其Debye温度(92K)下的导热系数．温度在20K以上时，模拟结果和实验值吻合较好，说明固态Ar的量子化效应对其热传导性能影响不大，温度低于20K时，由于模拟区域对长波声子的裁剪作用使得模拟结果比实验值低．在此基础上，使用经典分子动力学基于三向、两向周期性边界条件的各向异性非平衡态薄膜模型，模拟了超薄Ar膜在40K的导热系数，2种模型给出了具有相同变化趋势的薄膜热传导特性曲线，即：随着膜厚的增加，导热系数增大，且模拟结果同模拟区域横截面大小无关．在相同条件下，2种模型得到的氩膜导热系数相差10％左右．

Molecular dynamics simulation of thermal conductivity of argon thin film

Thermal conductivities of bulk argon below its Debye temperature are calculated by equilibrium molecular dynamics (EMD) simulation method without any correction for quantum effects. The classical molecular dynamics (MD) model gives a fair approximation of thermal conductivities to the experimental data above 20 K. This means that the quantum effects on thermal conductivity are relatively small. When the temperature is below 20 K, the MD results are lower than the experimental data due to the frequency cutoff of phonons spectra imposed by the simulation domain. Inhomogeneous non equilibrium molecular dynamics (NEMD) simulation models with three or two direction periodic condition are used to study the thermal conductivity of argon thin film. Simulation results of the two models give similar characteristic curves of the thin film thermal conductivities, that is, with the increase of thickness, the thermal conductivity of thin film increases, and the MD result is independent of the cross sectional area. The difference between the results produced by the two NEMD models under the same initial parameters is about 10 percent.