Absolutely Localized Projection-Based Embedding for Excited States.

Area of Science:

• Quantum chemistry
• Computational physics
• Theoretical chemistry

Background:

• Quantum embedding methods enable accurate calculations of complex systems by combining different theoretical approaches.
• Traditional methods face computational limitations for large systems, especially for excited states.

Purpose of the Study:

• To extend absolutely localized projection-based quantum embedding for studying local excited states.
• To improve computational efficiency and accuracy in wave function in density functional theory (WF-in-DFT) calculations.
• To investigate the treatment of environment response and charge-transfer states.

Main Methods:

• Utilized absolutely localized projection-based quantum embedding.
• Applied equation-of-motion coupled-cluster singles and doubles in DFT (EOM-CCSD-in-DFT) and time-dependent DFT in DFT (TDDFT-in-DFT).
• Calculated excited-state energy of green fluorescent protein.

Main Results:

• Achieved highly accurate excited-state energies compared to canonical methods.
• TDDFT-in-DFT often outperformed canonical TDDFT.
• Demonstrated elimination of spurious low-lying excitation energies and prevention of overdelocalization.
• Showed systematic convergence to full system results for green fluorescent protein.

Conclusions:

• Absolutely localized projection-based quantum embedding accurately treats local electronic excitations.
• This method makes computationally expensive wave function methods applicable to larger systems.
• Provides insights into chemical moieties polarizing during excitation.