Short-range DFT energy correction to multiconfigurational wave functions for open-shell systems

Area of Science:

• Computational chemistry
• Quantum chemistry
• Electronic structure theory

Background:

• Combining multiconfigurational wave functions and density functional theory (DFT) aims to leverage the strengths of both approaches.
• Wave Function Theory (WFT) combined with DFT (WFT-srDFT) often uses range separation, with DFT handling short-range interactions and WFT handling long-range ones.

Purpose of the Study:

• To uncover the limitations of WFT-srDFT in characterizing open-shell systems.
• To introduce and test strategies for accounting for spin polarization in WFT-srDFT.

Main Methods:

• Investigated the impact of spin polarization on short-range DFT exchange energy.
• Developed methods using spin-polarized electron density and short-range exact exchange.
• Tested approaches on H2 dissociation, triplet atom/diradical energy gaps, and Ga2 low-lying states.

Main Results:

• Spin polarization significantly affects short-range DFT exchange energy, crucial for open-shell systems.
• The proposed spin-polarized WFT-srDFT methods improve the description of open-shell systems.
• Combining short-range DFT correlation with full-range WFT shows promise for open-shell molecules.

Conclusions:

• WFT-srDFT methods require explicit treatment of spin polarization for accurate open-shell system characterization.
• The developed spin-polarized approaches enhance the performance of WFT and WFT-srDFT.
• Short-range DFT correlation with full-range WFT offers a promising avenue for studying open-shell molecules.