Ab initio lattice thermal conductivity of bulk and thin-film α-AI2O3

The thermal conductivities (κ) of bulk and thin-film α-AI 2 O 3 are calculated from first principles using both the local density approximation (LDA) and the generalized gradient approximation (GGA) to exchange and correlation. The room temperature single-crystal LDA value ~39 W/m K agrees well with the experimental values ~352–39 W/m K, whereas the GGA values are much smaller ~26 W/m K. Throughout the temperature range, LDA is found to slightly overestimate ϰ, whereas GGA strongly underestimates it. We calculate the κ of crystalline α-AI 2 O 3 thin films and observe a maximum of 79% reduction for 10 nm thickness.