~9 and ~2 for solid-state calculations with 2×2×2 and 5×5×5 grids, respectively. We next calculated the two-phonon Raman rates with fixed linewidths, which are again in excellent agreement with the experimental rates (Figure ). We note that the choice of linewidth has a larger effect in this region than in the single-phonon Orbach region, and that, counterintuitively, the two-phonon Raman rates have a negative correlation with linewidth, i.e. the rates become slower with larger linewidths, which is the opposite behaviour of the singlephonon rates. This can be explained by the fact that for the Raman mechanism only the difference in the phonon energy ℏ𝜔 -ℏ𝜔′ must match the difference in electronic energy 𝐸 M -𝐸 N , which allows many pairs of phonons to cause a transition between ground doublet states. When the linewidths are larger, the phonons' lineshapes extend to higher energies, resulting in smaller Bose-Einstein occupation factors and hence a reduction in the magnitude of these contributions.