Optimal Small Basis Set and Geometric Counterpoise Correction for DFT Computations.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Density Functional Theory (DFT) calculations rely on basis sets and corrections like geometric counterpoise (gCP) for accuracy.
• Evaluating the performance of various basis sets and gCP schemes is crucial for reliable computational chemistry results.

Purpose of the Study:

• To assess the performance of small basis sets with geometric counterpoise (gCP) corrections in DFT.
• To introduce and validate a simplified gCP scheme termed unity-gCP.
• To identify optimal basis sets balancing accuracy and computational cost.

Main Methods:

• Systematic examination of small and medium-sized basis sets.
• Application and evaluation of the original gCP correction scheme and a simplified unity-gCP scheme.
• Development and testing of a modified basis set, vDZ+(2d), derived from vDZP.

Main Results:

• The 6-31+G(2d) basis set demonstrates an optimal balance between accuracy and computational efficiency.
• The unity-gCP scheme provides a reasonable correction for arbitrary basis sets.
• Less balanced basis sets, even larger ones, can lead to significant inaccuracies and overcorrections with gCP.
• The 6-31+G(2d) basis set shows small gCP magnitudes, yielding adequate results even without correction.
• The newly developed vDZ+(2d) basis set generally improves upon the vDZP basis set.

Conclusions:

• The 6-31+G(2d) basis set is recommended for DFT calculations requiring a balance of accuracy and efficiency.
• The unity-gCP scheme offers a practical approach for basis set correction.
• Careful validation of gCP is necessary for specific basis sets to avoid overcorrection.
• The vDZP and vDZ+(2d) basis sets provide efficient alternatives to larger basis sets for DFT.