The behavior of density functionals with respect to basis set. I. The correlation consistent basis sets.

Area of Science:

• Computational chemistry
• Quantum chemistry

Background:

• Density functional theory (DFT) is a widely used quantum mechanical modeling method.
• Accurate prediction of molecular geometries and atomization energies is crucial for chemical research.

Purpose of the Study:

• To assess the accuracy of six common DFT functionals for predicting molecular geometries and atomization energies.
• To evaluate the impact of basis set size on the accuracy and precision of these DFT calculations.
• To compare the performance of hybrid and nonlocal DFT functionals.

Main Methods:

• Calculated geometries and atomization energies for first-row closed-shell molecules using six DFT functionals (B3LYP, B3PW91, B3P86, BLYP, BPW91, BP86).
• Employed correlation-consistent basis sets (cc-pVxZ and aug-cc-pVxZ, x=2-5).
• Performed statistical error analysis to determine accuracy and precision.

Main Results:

• B3LYP and B3PW91 functionals demonstrated smooth convergence towards the Kohn-Sham limit as basis set size increased.
• Nonlocal functionals (BLYP, BPW91, BP86) showed relative insensitivity to the choice of basis set.
• Accuracy and precision varied among the tested functionals and basis sets.

Conclusions:

• Hybrid DFT functionals, particularly B3LYP and B3PW91, offer reliable and systematically improvable results with increasing basis set size.
• Basis set choice is less critical for nonlocal functionals, but their convergence behavior differs.
• The study provides insights into selecting appropriate DFT functionals and basis sets for molecular property predictions.