A minimal auxiliary basis fills in the Hartree–Fock CBS limit: one minimal-basis calculation plus kernel ridge regression cuts error to 7.03 mHa
Approaching the complete basis set (CBS) limit in quantum chemistry usually means several mid-quality calculations plus extrapolation. Here a single Hartree–Fock calculation in the minimal pcseg-0 basis is augmented with an optimized, minimal complementary auxiliary basis set (CABS) singles correction, and kernel ridge regression learns the residual. On GDB-BSIE, CABSmin/pcseg-0 with atomic detrending gives an RMSE of 7.03 mHa against RHF/cc-pV5Z, at about 16% of the cost of a cc-pVDZ single point.