The calculated κ latt are compared to the κ/τ CRTA and τ CRTA in Figs 5(b) and 5(c), respectively, and values at 800 K are included in Table . The κ/τ CRTA saturate at higher temperatures where the C λ reach the Dulong-Petit limit, and differences in the harmonic function at higher T therefore reflect differences in the phonon group velocities. On the other hand, the τ CRTA decrease with temperature, as the increased thermal population of modes at higher T leads to stronger phonon scattering.