Static embedding with pair coupled cluster doubles based methods.

Area of Science:

• Quantum chemistry
• Computational chemistry
• Theoretical chemistry

Background:

• Quantum embedding methods are crucial for modeling large molecular systems.
• Pair-coupled cluster doubles (pCCD) excels at describing strongly correlated systems efficiently.
• Dynamic correlation effects require extensions beyond basic pCCD.

Purpose of the Study:

• To develop a novel wave function theory in density functional theory (WTF-in-DFT) embedding scheme.
• To incorporate linearized coupled-cluster corrections (LCCSD) for dynamic correlation.
• To apply the method to calculate vertical excitation energies of various molecular systems.

Main Methods:

• Development of a WTF-in-DFT embedding scheme using pCCD.
• Application of linearized coupled-cluster singles and doubles (LCCSD) for ground and excited states.
• Utilizing the equation of motion (EOM) formalism for excited-state calculations.
• Testing on water-ammonia complex, micro-solvated thymine, and uranyl tetrahalides.

Main Results:

• The EOM-pCCD-LCCSD-in-DFT method accurately calculates vertical excitation energies.
• The approach successfully models changes in excitation energies from fragments to supramolecular structures.
• Orbital entanglement and correlation analysis validated the embedding potential quality.

Conclusions:

• The proposed EOM-pCCD-LCCSD-in-DFT method is a promising computational tool for excited-state calculations in large molecules.
• This hybrid quantum embedding scheme effectively balances accuracy and computational cost.
• The method provides reliable insights into electronic excited states of complex chemical systems.