Impact of vacancy-type defects on thermal conductivity of β-SiC: Molecular dynamics versus an analytical approach

A molecular dynamics technique has been used to study the impact of single vacancies and small vacancy clusters/microvoids on thermal conductivity of β-SiC. It is found that single vacancies reduce thermal conductivity more significantly than do microvoids with the same total number of vacancies in the crystal. According to molecular dynamic result, the relative change of thermal resistivity linearly increases with vacancy concentration. This result is in contradiction with commonly used analytical approach prediction, where the dependence changes from linear at low concentrations to square root at higher values. The dependence on the volume fraction of microvoids switches from square root at small swelling values to nearly linear dependence at higher swelling. In the case of SiC, the molecular dynamic results obtained for vacancies and microvoids agree reasonably well with experimental values. The computational results are compared with the commonly used Debye-Callaway model. A possible way to modify the Debye-Callaway model is discussed.