where κ κ κ λ are the microscopic contributions to the κ κ κ latt from individual phonon modes λ with heat capacities C λ , group velocities ν ν ν λ and lifetimes τ λ , and the sum is normalised by the cell volume V and the number of phonon wavevectors q q q, N, included in the summation. (The analysis was applied to the scalar κ latt by taking the scalar average of κ κ κ/τ CRTA and choosing the τ CRTA to be consistent with the κ latt .)