Optimally Tuned Multiconfigurational Short-Range DFT for Linear Response Properties.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Multiconfigurational short-range density functional theory (MC-srDFT) integrates wave function theory and DFT.
• MC-srDFT lacks established methods for selecting its range-separation parameter.
• Existing methods often use a universal parameter, limiting accuracy.

Purpose of the Study:

• Develop a theoretically grounded protocol for determining the system-specific range-separation parameter in MC-srDFT.
• Improve the accuracy of static and dynamic dipole polarizability calculations.
• Provide a more rigorous approach compared to using universal parameters.

Main Methods:

• Introduced an optimal-tuning scheme based on enforcing correct electron density decay.
• Determined the range-separation parameter using the Extended Koopmans' Theorem (EKT) and ionization potential.
• Applied MC-srDFT with full linear response and its extended random phase approximation (ERPA) variant.

Main Results:

• The optimal-tuning scheme successfully determined system-specific range-separation parameters.
• Calculated static and dynamic dipole polarizabilities for molecular systems.
• Demonstrated substantial improvement in polarizability accuracy compared to a universal parameter (μ = 0.4 bohr⁻¹).

Conclusions:

• The proposed optimal-tuning scheme provides a theoretically sound method for MC-srDFT parameter selection.
• This approach significantly enhances the accuracy of polarizability predictions.
• The method offers a more reliable alternative to universal parameters in MC-srDFT calculations.