Here, 𝐸 u XYL is the gas-phase energy functional, 𝑛 XYL is the electron density from a converged gasphase SCF, and 𝑛 &%' is the electron density from a converged CPCM SCF. For the four zwitterions, Δ𝐸 Z &%' value increases with ε and takes a significant magnitude of about 0.2 eV even at a low ε=2.0 (Figure ). It is also worth noting that Δ𝐸 Z &%' seems insensitive to the XC functional, as the Δ𝐸 Z &%' values calculated with BLYP and B3LYP are almost identical for the same molecule (Figure ). These observations indicate that the PCM field polarizes the electron density and causes non-trivial changes, even when a very low ε is applied to improve convergence.