The DFPT phonon dispersion of CuI is shown in Figure and shows good agreement with the experimental frequencies reported in the literature. The minor disparity, such as for the LO-TO splitting, may be attributed to the challenge of precisely capturing the dielectric constants in CuI, as discussed in the next section. This plot is accompanied by the corresponding spectral decomposition of the hole scattering rates at different T (Figure ), and shows that the high-frequency longitudinal optical mode T 2 (LO) is the main contributor to the e-ph scattering in CuI. Although the spectral decomposition encompasses both short-and long-range phonons, transport in CuI is mainly influenced by the latter ones (near Γ). This is due to the unique and curvy pocket present at the VBM of the electronic band structure of the material, allowing only transitions with small momentum transfer 𝐪. Figure represents the T 2 (LO) phonon mode of CuI at Γ (towards the X direction) with the Cu and I atoms moving in phase opposition with twice the displacement amplitude for Cu. The relative contribution to scattering increases with T due to the growing number of phonons that are thermally excited, as evidenced by the area under the curve of Figure expanding from 100 K to 400 K. This results in a decrease of the e-ph IBTE mobility with temperature, as shown in Figure . (b) Spectral decomposition of the hole scattering rates as a function of frequency at different temperatures. (c) Structure of CuI showing the atomic displacements corresponding to the longitudinal optical phonon mode at the Γ point (towards the X direction), viewed along the face diagonal, plotted using VESTA. Cu and I atoms in blue and green, respectively.