Beyond Kohn-Sham Approximation: Hybrid Multistate Wave Function and Density Functional Theory.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Standard density functional theory (DFT) methods struggle with systems exhibiting strong electron correlation.
• Accurately describing conical intersections in photochemical processes remains a challenge for existing computational methods.
• Multiconfigurational approaches are computationally expensive for large systems.

Purpose of the Study:

• To present a novel Multistate Density Functional Theory (MSDFT) method.
• To enable the simultaneous treatment of ground and excited electronic states.
• To develop a robust method for systems with strong correlation and complex potential energy surfaces.

Main Methods:

• The MSDFT method combines multiconfigurational concepts with Kohn-Sham DFT (KSDFT).
• A dynamic-then-static framework is employed to incorporate both dynamic and static electron correlation.
• Block-localized KSDFT is used for dynamic correlation, followed by Hamiltonian diagonalization for static correlation.

Main Results:

• The developed MSDFT method successfully treats systems with strong electron correlation.
• It accurately describes the dimensionality of conical intersections between dissociative potential energy surfaces.
• The method demonstrates applicability to photochemical processes involving conical intersections.

Conclusions:

• MSDFT offers a hybrid approach, merging wave function theory and DFT.
• It provides a computationally efficient alternative for strongly correlated systems that are too large for accurate wave function methods.
• MSDFT is a promising tool for studying complex photochemical dynamics.