Density Functional Model for Nondynamic and Strong Correlation.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Materials Science

Background:

• Accurately describing electron correlation is crucial for computational chemistry.
• Left-right nondynamic/strong correlation presents a significant challenge for standard density functional theory (DFT) methods.
• Existing DFT models often struggle with bond dissociation and related phenomena.

Purpose of the Study:

• To develop a single-term density functional model for left-right nondynamic/strong electron correlation.
• To improve the accuracy of Kohn-Sham density functional theory (KS-DFT) for challenging electronic correlation effects.
• To create a computationally efficient model with minimal empirical parameters.

Main Methods:

• Derivation of a new correlation functional based on adiabatic connection modeling and physical arguments.
• Incorporation of the Becke'13 model for correlation potential energy.
• Development of a density-functional correction to reduce fractional spin error.
• Self-consistent-field (SCF) implementation and testing.

Main Results:

• The new functional satisfies known scaling relationships for correlation.
• Substantial reduction in fractional spin error achieved.
• Model recovers significant left-right nondynamic/strong correlation during bond dissociation.
• Reasonable performance for atomization energies and singlet-triplet energy splittings.

Conclusions:

• The developed single-term density functional model effectively addresses left-right nondynamic/strong electron correlation.
• The model demonstrates feasibility within the single-determinant KS scheme.
• This approach offers a promising avenue for improving DFT accuracy in computational chemistry.