All three compounds show sub-picosecond averaged lifetimes τ CRTA . The τ CRTA vary by ∼ 2.6× and show the opposite trend to the harmonic terms, i.e. are shortest for STO and longest for BTO. The combination of the 2.7× larger κ/τ CRTA and shorter averaged lifetimes of STO compared to BTO result in the two systems having similar κ ave , while the low group velocities and intermediate τ CRTA of CTO lead to the lowest lattice thermal conductivity of the three systems. The long τ CRTA of BTO are perhaps also unexpected given the localised A-site feature in the phonon DoS (c.f. Fig. ). However, following a similar thought process to the analysis of the κ/τ CRTA , the larger radius r A of the Ba cation (c.f. Table ) may limit its ability to rattle and limit the expected phonon scattering.