Coordinate Descent Full Configuration Interaction.

Area of Science:

• Quantum Chemistry
• Computational Physics

Background:

• Accurate electronic structure calculations are crucial for understanding molecular properties.
• Full Configuration Interaction (FCI) provides exact solutions but is computationally expensive.
• Developing efficient methods to approximate FCI is essential for practical applications.

Purpose of the Study:

• To introduce and validate a novel algorithm, coordinate descent FCI (CDFCI), for efficient electronic structure ground-state calculations.
• To demonstrate CDFCI's capability in handling both static and dynamic electron correlation.
• To achieve high accuracy in variational energy calculations for challenging molecular systems.

Main Methods:

• Reformulation of the FCI eigenvalue problem as an unconstrained nonconvex optimization problem.
• Application of an adaptive coordinate descent method with a deterministic compression strategy.
• Adaptive updating of determinants based on their importance for computational efficiency.

Main Results:

• CDFCI achieves high accuracy (10^-3 mHa) for the nitrogen dimer binding curve in the cc-pVDZ basis.
• The algorithm efficiently handles strongly correlated systems, as shown with the chromium dimer in the Ahlrichs VDZ basis.
• State-of-the-art variational energies were produced for the tested molecular systems.

Conclusions:

• CDFCI offers an efficient and accurate approach for electronic structure calculations within the FCI framework.
• The adaptive determinant updating strategy enhances computational performance.
• CDFCI shows significant promise for accurate quantum chemistry simulations of complex molecules.