Finally, we consider incorporation of low-dielectric boundary conditions as a means to mitigate charge delocalization. In previous work, 105 we showed that a continuum solvation model with a dielectric constant = 4 eliminates oscillatory behavior in MBE(n) as applied to a large enzyme model with individual amino acids as fragments. The boundary conditions were implemented using a polarizable continuum model (PCM), 137 not as a representation of an aqueous environment but rather to reduce charge delocalization that can lead to a vanishing gap and concomitant convergence problems in large-molecule DFT calculations. These problems are sometimes ameliorated by electrostatic stabilization of the molecular surface. Notably, convergence is also improved using the BH&H-LYP functional rather than B3LYP or GGAs. MBE(n)-SCAN results with boundary conditions corresponding to = 4 are shown in Fig. but the PCM fails to mitigate the oscillations. As compared to our calculations on proteins, 105 the fragments used here are rather small and fit within the molecular surface used by the solvent model. In other words, intermolecular charge delocalization across hydrogen bonds remains possible, and divergent results for MBE(n) suggests that this behavior is not mitigated by the low-dielectric PCM.