Systematically convergent basis sets for explicitly correlated wavefunctions: The atoms H, He, B–Ne, and Al–Ar

TLDR

Correlation-consistent basis sets have been optimized for explicitly correlated F12 methods. The authors benchmarked the new basis sets on 15 chemical reactions to assess relative energetic accuracy. The cc‑pVnZ‑F12 sets recover nearly 99 % of MP2 valence correlation energy for first‑row atoms and 97–99 % for second‑row atoms, achieving markedly faster convergence to the complete basis set limit in MP2‑F12/3C calculations than standard aug‑cc‑pVnZ sets.

Abstract

Correlation consistent basis sets have been optimized for use with explicitly correlated F12 methods. The new sets, denoted cc-pVnZ-F12 (n=D,T,Q), are similar in size and construction to the standard aug-cc-pVnZ and aug-cc-pV(n+d)Z basis sets, but the new sets are shown in the present work to yield much improved convergence toward the complete basis set limit in MP2-F12/3C calculations on several small molecules involving elements of both the first and second row. For molecules containing only first row atoms, the smallest cc-pVDZ-F12 basis set consistently recovers nearly 99% of the MP2 valence correlation energy when combined with the MP2-F12/3C method. The convergence with basis set for molecules containing second row atoms is slower, but the new DZ basis set still recovers 97%–99% of the frozen core MP2 correlation energy. The accuracy of the new basis sets for relative energetics is demonstrated in benchmark calculations on a set of 15 chemical reactions.