The phonon band-centre for a given solid electrolyte is defined as the "centre-of-mass" when integrating over the full vibrational density-of-states (DOS), and can be computed for the full set of phonon modes, or for a subset using the atom-projected phonon DOS . While this descriptor is much cheaper to compute than directly calculating ionic conductivities; for example, from molecular dynamics simulations; it neglects the effect of temper-ature on ion dynamics because the phonon DOS is computed within the harmonic approximation at 0 K . The conventional phonon band-centre therefore not expected to be able to fully describe a superionic transition-in particular for a type-II transition where the host-framework structure does not change. At non-zero temperatures phonon modes are not equally populated, but instead are populated according to Bose-Einstein statistics. A Bose-Einstein-weighted phonon band-centre, for example, therefore might better describe the effects of changing temperature on ionic conductivity than a conventional unweighted phonon band-centre, and may therefore be able to describe the changes in ionic conductivity that occur across a superionic transition.