Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory: Multireference Advantages with the Practicality...

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Density Functional Theory (DFT) is crucial for routine computations but struggles with open-shell systems.
• Linear Response Time-Dependent DFT (LR-TDDFT) has limitations in modeling excited states and core excitations.

Purpose of the Study:

• To introduce Mixed-Reference Spin-Flip Time-Dependent DFT (MRSF-TDDFT) as a solution to existing DFT limitations.
• To highlight MRSF-TDDFT's capability in accurately describing challenging electronic systems.

Main Methods:

• Utilizing the mixed-reference (MR) and spin-flip (SF) formalisms within Time-Dependent DFT (TDDFT).
• Applying the practical linear response (LR) formalism to the MR-SF-TDDFT approach.

Main Results:

• MRSF-TDDFT effectively addresses the limitations of single-reference DFT for diradicals and bond-breaking.
• MRSF-TDDFT accurately models challenging excited states, including conical intersections and doubly excited states, and core-level excitations.

Conclusions:

• MRSF-TDDFT provides a robust and accurate alternative for computational problems where traditional methods fail.
• The practicality of the LR formalism suggests MRSF-TDDFT will become a widely adopted tool for routine computational chemistry.