Many-Body Expanded Full Configuration Interaction. I. Weakly Correlated Regime

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical chemistry

Background:

• Computational chemistry has become essential alongside traditional experimental chemistry.
• Full configuration interaction (FCI) methods are regaining prominence but require robust and versatile implementations.
• The many-body expanded FCI (MBE-FCI) formalism offers a path to FCI-level accuracy for larger systems.

Purpose of the Study:

• To present performance and feature enhancements of the MBE-FCI method.
• To demonstrate the capabilities of MBE-FCI for medium to large one-electron basis sets.
• To showcase MBE-FCI's ability to compute near-exact ground state energies for weakly correlated molecules.

Main Methods:

• Implementation of the many-body expanded full configuration interaction (MBE-FCI) formalism.
• Application to medium to large one-electron basis sets.
• Calculation of ground state energies for weakly correlated molecules across various spin multiplicities.

Main Results:

• Demonstration of the MBE-FCI method's effectiveness.
• Successful computation of near-exact ground state energies.
• Validation of the approach for molecules with varying spin multiplicities.

Conclusions:

• The MBE-FCI method is a promising avenue for achieving FCI-level accuracy in computational chemistry.
• The enhancements presented make MBE-FCI more robust and versatile for practical applications.
• This work establishes MBE-FCI as a viable tool for studying weakly correlated molecular systems.