Comparison of Explicitly Correlated Methods for Computing High-Accuracy Benchmark Energies for Noncovalent...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Noncovalent interactions are crucial in chemistry and biology.
• Accurate calculation of interaction energies is essential for understanding molecular systems.
• Explicitly correlated methods offer a pathway to high accuracy.

Purpose of the Study:

• To evaluate the reliability of explicitly correlated methods for benchmark noncovalent interaction energies.
• To compare the performance of standard augmented correlation-consistent (aXZ) and specialized F12 basis sets.
• To assess convergence behavior and computational efficiency.

Main Methods:

• Computations using aug-cc-pVXZ (aXZ) and cc-pVXZ-F12 (XZ-F12) basis sets.
• Explicitly correlated coupled cluster singles and doubles [CCSD-F12n (n = a, b, c)] with perturbative triples [(T**)].
• Comparison against estimates of the complete basis set (CBS) limit.

Main Results:

• aXZ basis sets yielded smaller errors compared to the CBS limit than XZ-F12 basis sets.
• The F12b ansatz demonstrated the lowest average errors for triple-zeta (aTZ) and larger basis sets.
• CCSD(T**)-F12b/aXZ exhibited the fastest basis set convergence.

Conclusions:

• Explicitly correlated methods with standard aXZ basis sets provide reliable benchmark noncovalent interaction energies.
• CCSD(T**)-F12b/aTZ and focal point schemes offer comparable accuracy and efficiency.
• These methods are computationally more efficient than large-basis conventional CCSD(T).