To evaluate the atom-projected phonon density of states (PDoS) curves, the phonon frequencies were interpolated onto uniform Γ-centered q q q-point meshes with 28 × 13 × 36, 28 × 28 × 28, and 40 × 40 × 40 subdivisions for the Pnma, R3m, and rocksalt phases, respectively. The phonon dispersion curves were evaluated by interpolating the frequencies onto strings of q q q-points passing through the high-symmetry points in the respective Brillouin zones. Non-analytical corrections at q q q → Γ were included to model the splitting between the longitudinal and transverse optic modes (i.e., LO/TO splitting) using the approach in Ref. . The required Born effective charges Z Z Z * and high-frequency dielectric constants ε ε ε ∞ were computed using PBEsol+D3 and density-functional perturbation theory (DFPT). The κ latt was calculated within the single-mode relaxation-time approximation (SM-RTA) based on modal properties calculated on Γ-centered q q qpoint meshes with 16 × 8 × 16 and 24 × 24 × 24 subdivisions for the Pnma and R3m phases, respectively. We found that LO/TO splitting has a negligible impact on the κ latt of the four systems (Fig. ).