Basis Set Extrapolations for Density Functional Theory

Basis set extrapolation is a common technique in wavefunction theory used to squeeze better performance out of the highest affordable level of theory by combining it with lower quality calculations. In this work, I present analogous techniques for basis set extrapolation in density functional theory, focusing on [2,3]-ζ calculations and including double hybrid and dispersion-corrected functionals. My recommendations are based on basis set limit data from finite element calculations and estimates of basis set limits for double hybrid corrections, and they are validated using the GMTKN55 and NCDT datasets. A short review of extrapolation methods for Hartree-Fock calculations based on modern finite element data is carried out to inform this work. Extrapolation of [2,3]-ζ calculations in def2-Xzvpd and cc-pvXz-pp basis sets with the proposed recipes routinely matches and sometimes outperforms 4-ζ calculations at a fraction of the cost. The methods are implemented in Psi4, allowing for an automated and intuitive application.