Functional-Based Description of Electronic Dynamic and Strong Correlation: Old Issues and New Insights

Area of Science:

• Quantum Chemistry
• Computational Materials Science

Background:

• Kohn-Sham density functional theory (KS-DFT) excels at dynamic correlation, while reduced density matrix functional theory (RDMFT) handles strong correlation.
• Combining KS-DFT and RDMFT offers complementary benefits but faces challenges with correlation double-counting.

Purpose of the Study:

• Develop a novel short-range corrected 1-RDM functional (ωP22) integrating KS-DFT and RDMFT advantages.
• Address the issue of correlation double-counting in combined theoretical frameworks.
• Enhance the accuracy of electronic structure calculations for diverse chemical systems.

Main Methods:

• Development of a short-range corrected 1-RDM functional, denoted ωP22.
• Systematic testing of ωP22 against established benchmarks for thermochemistry, nonbonded interactions, and bond dissociation energies.
• Evaluation of ωP22 performance on systems with fractional spins and varying bond types (single, multiple, equilibrium, dissociation).

Main Results:

• The ωP22 functional demonstrates superior performance compared to existing 1-RDM functionals across tested properties.
• ωP22 significantly reduces systematic errors in calculations involving fractional spins.
• Accurate prediction of energies at both equilibrium and dissociated bond distances for various bond types.

Conclusions:

• ωP22 effectively balances the treatment of dynamic and strong electron correlation.
• The developed functional overcomes limitations of conventional KS-DFT and RDMFT methods.
• This work paves the way for new approximate functionals and advanced computational chemistry applications.