strength increases. For pPF(2880,10)/cc-pVQZ, we see microHartree error with the largest coupling strength (λ z = 0.1), and we see ∼100 microHartree error for pPF(60,10)/cc-pVDZ at this coupling strength. Because the dipole self-energy is quadratic in the coupling strength, we expect to see that the disparity between pQED and scQED will become more dramatic as the coupling strength increases. The progression shown in Figure shows that differences between the exact and projected dipole self-energy operators have not been fully resolved even when using a cc-pVQZ orbital basis and 2880 many-electron states.