Automatically generated Coulomb fitting basis sets: design and accuracy for systems containing H to Kr

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Auxiliary basis sets (ABS) are crucial for accelerating quantum chemical calculations in intermediate-sized systems by fitting charge density.
• Existing ABS designs require significant effort and may not optimally adapt to specific orbital basis sets (OBS).
• The performance of quantum chemical methods is often limited by the choice of ABS and OBS.

Purpose of the Study:

• To develop and evaluate a fundamentally new, dynamically generated auxiliary basis set (auto-ABS).
• To assess the accuracy and performance of auto-ABS across various quantum chemical methods and systems.
• To compare the auto-ABS approach with existing fixed-size ABS and universal fitting sets.

Main Methods:

• A novel approach for creating an ABS dynamically based on the specific orbital basis set (OBS) used in calculations.
• Introduction of a parameter to control the coalescence of fitting functions and the number of functions in the auto-ABS.
• Systematic accuracy studies of the auto-ABS for small chemical systems (H-Kr) and comparison with universal fitting sets for 180 compounds.

Main Results:

• Errors in Coulomb energy computed using auto-ABS are small compared to Hartree-Fock energy errors from incomplete OBS.
• Auto-ABS demonstrates improved accuracy with increasing OBS size (quality), unlike fixed-size ABS.
• The performance of auto-ABS is comparable to or better than recently proposed universal fitting sets.

Conclusions:

• Dynamically generated auxiliary basis sets (auto-ABS) offer a promising avenue for enhancing computational efficiency and accuracy in quantum chemistry.
• The auto-ABS approach provides a flexible and adaptive alternative to traditional fixed-size auxiliary basis sets.
• This method shows significant potential for broader application in various quantum chemical calculations.