Communication: Quasi-robust local density fitting.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Electronic Structure Theory

Background:

• Standard density fitting methods can introduce unphysical long-range contributions.
• Incomplete auxiliary basis sets are a primary cause of these errors.
• Accurate electronic structure calculations require robust density fitting approaches.

Purpose of the Study:

• To develop a quasi-robust density fitting formulation that recovers spatial locality.
• To mitigate unphysical long-range errors in approximate charge densities.
• To provide a stable and accurate alternative to standard density fitting.

Main Methods:

• A quasi-robust density fitting formulation is introduced.
• Spatial locality is recovered by permitting a small linear error.
• The fitting procedure optimizes the Coulomb potential of the approximate charge density.

Main Results:

• The proposed method recovers spatial locality, unlike standard approaches.
• The linear error is minimized through Coulomb potential optimization.
• The method demonstrates stability and near-standard accuracy in practical calculations.

Conclusions:

• The quasi-robust density fitting method effectively reduces unphysical long-range errors.
• It offers a practical balance between accuracy and computational efficiency.
• This formulation is suitable for use with standard density fitting basis sets.