Density Functional Extension to Excited-State Mean-Field Theory.

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• Excited-state mean-field theory (ESMFT) is a computational method for studying electronic excited states.
• Accurately describing electron correlations, especially weak ones, remains a challenge in electronic structure calculations.
• Existing methods may struggle with specific aspects of excited states, such as charge transfer phenomena.

Purpose of the Study:

• To develop an extension of excited-state mean-field theory.
• To incorporate density functional components to account for weak electron correlations.
• To improve the description of excited electronic states, particularly charge transfer states.

Main Methods:

• Augmenting the energy expression of excited-state mean-field theory with density functional components.
• Maintaining a variational and time-independent approach.
• Allowing for state-specific relaxation of all electron orbitals.

Main Results:

• The extended method demonstrates clear advantages for single-component charge transfer states.
• The approach avoids reliance on Kohn-Sham orbital energy differences, crucial for charge transfer.
• The method's reliability is currently limited for states with significant multiple particle-hole transitions.

Conclusions:

• The developed method offers a promising, variational approach for excited-state calculations.
• It shows particular utility in modeling charge transfer excitations.
• Further refinements are needed to enhance its accuracy for more complex excited states.