measuring temperature-dependent diffusion coefficients (or ionic conductivity) allows for the activation barrier 𝐸 𝐴 to be defined as a macroscopic thermodynamic quantity, a quantity that reflects (in some average way) the underlying instantaneous energy landscape that is encountered by the ions at the microscopic level. Although it is well-known that thermal energy is ultimately responsible for ion transport, it is not typical to consider this energy from a phonon perspective, where thermal energy is quantized by the number of phonons. In the phonon perspective, the frequency of the phonon mode and the phonon occupation number (# phonons) ultimately define the thermal energy contained by the ion.