Accurate extrapolation of MP2 correlation energies for small correlation-consistent core-valence basis sets

Abstract: The Atom-Calibrated Basis-set Extrapolation (ACBE) method is introduced as a robust approach for extrapolating MP2 correlation energies from small basis sets. Unlike conventional extrapolation techniques, ACBE incorporates system- and environment-specific parameters to enhance predictive accuracy, effectively mitigating errors associated with finite basis sets. Evaluated using the aug-cc-pwCV$n$Z basis set family across a diverse set of molecular systems, including first- and second-row species, ACBE consistently delivers reliable energy estimates, even when double- and triple-zeta basis sets are employed. These results highlight the computational efficiency of the method, making it a promising option for large MP2 studies.