A Valence-Bond-Based Multiconfigurational Density Functional Theory: The λ-DFVB Method Revisited.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• The λ-DFVB method addresses electron correlation errors in multireference calculations.
• Previous schemes, like λ-DFVB(K), required significant computational resources.

Purpose of the Study:

• To introduce a simplified and computationally efficient variant of the λ-DFVB method.
• To develop a new scheme, λ-DFVB(IS), using natural orbital occupation numbers (NOONs) for the parameter λ.

Main Methods:

• The study revisits the valence-bond-based multireference density functional theory (λ-DFVB).
• A novel parameterization, λ-DFVB(IS), is proposed, defining λ based on NOONs.
• The method avoids additional self-consistent field calculations post-VBSCF, reducing computational cost.

Main Results:

• λ-DFVB(IS) demonstrates simplified calculations compared to λ-DFVB(K).
• The method shows robust performance across various molecular properties, including bond lengths, energies, and reaction barriers.
• Accuracy is comparable to high-level methods like CASPT2.

Conclusions:

• λ-DFVB(IS) offers a computationally efficient and accurate approach for multireference calculations.
• The method provides a practical alternative for studying complex molecular systems.
• This advancement enhances the applicability of valence-bond-based DFT methods.