Here, ϕ σ s 0 (r) is the electrostatic potential generated by the ground-state polarization charge, σ s 0 (r). As discussed in Refs. 16 and 21, the W 0,k(0) term has sometimes been omitted from nonequilibrium polarization treatments, but is necessary when the "Marcus partition" into fast and slow components is used, corresponding to Eq. (12).