Similarly, In Figure , the curves represent the absolute energy error vs coupling strength of the pPF(N el ,10) ground-states in each basis set, where we have fixed N el at the value where we observed the energy converge in Figure . All methods show errors of less than a mi-croHartree for coupling strengths smaller than ∼0.01 atomic units but show increasing errors as the coupling FIG. . Absolute error of pPF(N,10) relative to PF-FCI-10 computed within the cc-pVDZ, cc-pVTZ, and cc-pVQZ basis sets, where we plot this error as a function of the percentage of the FCI electronic states used to parameterize the pPF(N,10) method. The photon frequency in each case is tuned to the S0 → S2 transition, and λz is fixed at 0.02 atomic units.