A basis-set error correction based on density-functional theory for strongly correlated molecular systems.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Basis-set incompleteness is a significant challenge in electronic structure calculations, particularly for strongly correlated molecular systems.
• Existing methods struggle to accurately capture short-range correlation effects in finite basis sets.
• Range-separated density-functional theory (RSDFT) offers a promising avenue for addressing these limitations.

Purpose of the Study:

• To extend a recently developed basis-set incompleteness correction to strongly correlated molecular systems.
• To investigate the performance of RSDFT-type complementary density functionals for recovering missing correlation energies.
• To analyze the impact of on-top pair densities and spin polarization on the accuracy of the correction.

Main Methods:

• Extension of a density-functional theory (DFT)-based basis-set correction to strongly correlated molecular systems.
• Utilizing a mapping between wave-function calculations and RSDFT via an effective non-divergent interaction.
• Exploring various complementary functional approximations with spin-multiplet degeneracy and size consistency properties.

Main Results:

• The explicit dependence on the on-top pair density effectively removes spin polarization dependence without sacrificing accuracy.
• The basis-set correction achieves chemical accuracy for atomization energies with triple-ζ basis sets for most studied molecules (H10, N2, O2, F2).
• Smooth potential energy curves are obtained across the entire range of internuclear distances.

Conclusions:

• The proposed basis-set incompleteness correction is highly effective for strongly correlated molecular systems.
• The method provides accurate and reliable results, particularly for molecular dissociation processes.
• This approach offers a robust way to improve the accuracy of quantum chemical calculations in finite basis sets.