Effect of grain boundary angle on the thermal conductivity of nanostructured bicrystal ZnO based on the molecular dynamics simulation method

Abstract

ZnO is a widely used semiconductor material due to its excellent physical and mechanical properties. The thermal transport behavior across a single grain boundary (GB) of bicrystal ZnO with varying tilt angles from 5.45° to 67.38° was investigated using a nonequilibrium molecular dynamics simulation. The GB energy and Kapitza resistance as a function of tilt angle were determined and parameters of the extended Read-Shockley model were calculated. The Kapitza resistance varied monotonically with a GB angle <36° and was nearly constant when the angle was >36°. Furthermore, effective thermal conductivity and Kapitza resistance were found to depend strongly on the sample length and temperature. Finally, we compared the phonon density of states of the two types of GBs and found a mismatch in the low frequency that might explain the effect of the GBs structures on heat conduction.