Accuracy of Different Electronic Basis Set Families for Anharmonic Molecular Vibrations: A Comprehensive Benchmark...

Area of Science:

• Computational Chemistry
• Molecular Spectroscopy
• Quantum Chemistry

Background:

• Accurate prediction of molecular vibrational spectra is crucial for understanding chemical properties and reactions.
• Electronic basis sets significantly influence the accuracy of computational spectroscopy.
• Previous studies have focused on split-valence basis sets for fundamental vibrational calculations.

Purpose of the Study:

• To benchmark the accuracy and convergence of various electronic basis set families for anharmonic vibrational spectroscopic calculations.
• To compare different basis sets using vibrational self-consistent field (VSCF) and VSCF-perturbation theory (VSCF-PT2) methods.
• To provide guidance on selecting basis sets that balance accuracy and computational cost for diverse molecular systems.

Main Methods:

• Assessment of 39 basis sets from Jensen, Dunning, Calendar, Karlsruhe, and Sapporo families.
• Application of VSCF and VSCF-PT2 algorithms with MP2 and B3LYP-D potentials.
• Comparison of calculated fundamental transitions, excited states, and intensities with experimental data.
• Statistical error analysis for accuracy and precision evaluation.

Main Results:

• A considerable improvement in calculated harmonic and anharmonic values is observed from small to medium (triple-ξ) basis sets.
• Basis set convergence becomes slow beyond the triple-ξ level, yielding nearly converged values.
• Basis sets with and without diffuse functions exhibit distinct accuracy and convergence behaviors.
• Basis set performance varies across different basis set families and computational methods.

Conclusions:

• Medium-sized basis sets (triple-ξ) offer a good balance between accuracy and computational efficiency for anharmonic vibrational spectroscopy.
• Larger basis sets provide marginal improvements, suggesting diminishing returns.
• The choice of basis set, including the presence of diffuse functions, is critical for accurate spectroscopic predictions.
• Recommendations are provided for selecting cost-effective basis sets for large molecules, considering accuracy and computational time.