Configuration interaction extension of AGP for incorporating inter-geminal correlations.

Area of Science:

• Quantum Chemistry
• Computational Physics
• Electronic Structure Theory

Background:

• The antisymmetrized geminal power (AGP) framework is a powerful tool for describing correlated electronic systems.
• Incorporating inter-geminal correlations is crucial for accurate electronic structure calculations, but often computationally challenging.

Purpose of the Study:

• To develop a computationally tractable class of antisymmetrized geminal power configuration interaction (AGP-CI) wave functions.
• To enhance the AGP framework by including inter-geminal correlations via a configuration interaction (CI) expansion.
• To improve the accuracy of electronic structure calculations, especially for strongly correlated systems.

Main Methods:

• Rewriting the AGP-CI ansatz as a linear combination of AGPs (LC-AGP) for computational tractability.
• Utilizing standard AGP machinery for computing overlaps and Hamiltonian matrix elements.
• Reorganizing the ansatz into a compact LC-AGP with a deformation parameter τ for controlled approximation.

Main Results:

• The proposed AGP-CI wave functions achieve consistently high accuracy across benchmark applications.
• The new AGP-CI method outperforms the standard LC-AGP approach.
• Improved performance is particularly notable for systems with more electrons and in strongly correlated regimes.

Conclusions:

• The developed AGP-CI wave functions provide a significant advancement in describing electron correlations.
• This method offers a computationally efficient and accurate approach for complex quantum systems.
• The findings pave the way for more precise electronic structure calculations in challenging chemical and physical problems.