晶格失配对超晶格法向导热系数影响的分子动力学模拟

Molecular dynamics simulation of the influence of lattice mismatch on cross-plane superlattice thermal conductivity

采用非平衡态分子动力学方法模拟了超晶格的法向导热系数随周期长度的变化关系.模拟结果表明,在晶格匹配的超晶格中,当周期长度同声子平均自由程相当时,超晶格导热系数将出现最小值.而对于具有4%晶格失配的超晶格模拟结果却表明,超晶格导热系数随周期长度的增大而单调上升.这一研究结果表明,材料的晶格失配是大多数实验研究中没有发现超晶格最小导热系数的主要原因.

The dependence of superlattice thermal conductivity on period length is investigated by nonequilibrium molecular dynamics simulation. For perfectly lattice-matched superlattices, a minimum thermal conductivity is observed when the period length is of the order of the effective phonon mean free path. However, the simulation results of the superlattice with 4% lattice mismatch show that the thermal conductivity increases monotonically with the period length. These results indicate that lattice mismatch is the main reason why minimum thermal conductivity has not been observed in a large number of experimental studies.