A density-fitting implementation of the density-based basis-set correction method.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Basis set incompleteness is a major challenge in electronic structure calculations.
• Accelerating convergence to the complete-basis-set (CBS) limit is crucial for accurate predictions.
• Existing methods may be computationally expensive or lack efficiency.

Purpose of the Study:

• To implement and evaluate an efficient density-fitting version of the density-based basis-set correction (DBBSC) method.
• To assess the performance of DBBSC in accelerating basis set convergence for reaction energies.
• To compare DBBSC with the explicitly correlated MP2-F12 method.

Main Methods:

• Implementation of the density-based basis-set correction (DBBSC) method with density fitting in MOLPRO.
• Exploration of different basis-set correction density-functional approximations.
• Inclusion of complementary-auxiliary-basis-set single-excitation correction.
• Testing on a benchmark set of reaction energies at the second-order Møller-Plesset (MP2) level.

Main Results:

• The density-fitting DBBSC method significantly accelerates the basis set convergence of MP2 reaction energies.
• DBBSC provides a computationally less expensive approach compared to MP2-F12.
• The accuracy of DBBSC is found to be lower than that of the MP2-F12 method.

Conclusions:

• The density-fitting DBBSC method is an efficient tool for improving basis set convergence in quantum chemical calculations.
• DBBSC offers a practical balance between computational cost and accuracy for certain applications.
• Further exploration of DBBSC approximations may lead to enhanced accuracy.