Given that the electronic structure and atomic coordination environments remain constant, there is no indication that the saddle point energy should change appreciably during isotopic substitution. Although changes in the zero-point energy have been used as an explanation for the magnitude of Δ𝐸 A going from H + to D + in some materials, changes in the zero-point energy do not accurately capture the magnitude of Δ𝐸 A or the trend with increasing 𝐸 A in these Li + conductors.