Many-Body Basis Set Amelioration Method for Incremental Full Configuration Interaction.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Electronic Structure Theory

Background:

• Full configuration interaction (FCI) provides exact solutions but is computationally intractable for most systems.
• Incremental full configuration interaction (iFCI) offers a polynomial-cost approach to systematically approach the FCI limit.
• Applying iFCI to larger atomic orbital basis sets remains computationally demanding.

Purpose of the Study:

• Introduce the many-body basis set amelioration (MBBSA) method.
• Enable iFCI to be applied to larger atomic orbital basis sets.
• Reduce the computational cost of high-accuracy electronic structure calculations.

Main Methods:

• The many-body basis set amelioration (MBBSA) method is presented.
• MBBSA utilizes a series of cost-effective iFCI calculations.
• It approximates the correlation energy obtained from expensive, high-accuracy iFCI computations.

Main Results:

• MBBSA achieves approximations to total and relative energies within chemical accuracy.
• Compared to standard iFCI, MBBSA reduces computational cost by 60–92%.
• Larger molecular systems benefit most significantly from the cost reduction.

Conclusions:

• MBBSA enhances the applicability of iFCI to larger basis sets.
• The method demonstrates practical utility for studying complex chemical reactions.
• MBBSA facilitates accurate electronic structure studies of highly correlated systems.