Based on this model, we predict that nanostructuring to dimensions smaller than 20 nm would decrease the inplane and out-of-plane lattice thermal conductivities, respectively, from 2.27 W m -1 K -1 and 0.76 W m -1 K -1 to 1.87 W m -1 K -1 and 0.66 W m -1 K -1 at 1000 K. Nanostructuring to 10 nm is predicted to have a larger effect, reducing the thermal conductivity along the two directions to 1.64 W m -1 K -1 and 0.53 W m -1 K -1 . A larger reduction is predicted at lower temperatures, particularly below 300 K, where nanostructuring decreases the thermal conductivity by over a third.