For a more quantitative analysis, we replace the |Φ -λ λ ′ λ ′′ | 2 in Eq. 10 with a constant value P representing a weighted average of the P λ defined in Eq. 12. With this substitution, the κ κ κ is inversely proportional to P and a suitable value to reproduce the κ κ κ at a given temperature can be determined from a linear fit. In the same way as the τ CRTA are a weighted-average lifetime, the P are a weighted average of the Φ λ ,λ ′ ,λ ′′ /P λ . We note that, like the N 2 , the P scale with the size of the primitive cell and need to be multiplied by (3n a ) 2 to compare between systems. The values of P computed at T = 300 K are presented alongside the κ κ κ in Table . We also show the linear fits performed to determine these parameters, together with a comparison of the P to the frequency spectra of the P λ , in the ESI. † Finally, we can combine the averaged lifetimes τ CRTA with the P using Eq. 11 to determine a weighted average number of scattering pathways Ñ2 as: