Resonant Inelastic X-ray Scattering: How Well Does LR-TDDFT Perform?

Area of Science:

• * Quantum chemistry and spectroscopy.
• * Computational materials science.

Background:

• * Resonant inelastic X-ray scattering (RIXS) is a powerful spectroscopic technique for probing excited states.
• * Interpreting RIXS signals requires accurate and efficient spectral calculations.
• * Existing wave function-based methods (e.g., ADC) are computationally intensive.

Purpose of the Study:

• * To evaluate the performance of linear-response time-dependent density functional theory (LR-TDDFT) for RIXS spectral calculations.
• * To compare different LR-TDDFT approaches and functionals against established methods.
• * To demonstrate the applicability of LR-TDDFT for complex systems like C₆₀.

Main Methods:

• * Investigated two LR-TDDFT approaches: restricted-subspace and two-shot.
• * Benchmarked global hybrid, range-separated, and tailored range-separated functionals.
• * Used algebraic diagrammatic construction (ADC) as the reference method for small molecules.

Main Results:

• * LR-TDDFT, particularly with range-separated hybrid and most global hybrid functionals, shows good agreement with ADC.
• * Both restricted-subspace and two-shot LR-TDDFT approaches are effective.
• * Successfully computed the RIXS spectrum of C₆₀ using LR-TDDFT.

Conclusions:

• * LR-TDDFT provides a computationally efficient and accurate method for RIXS spectral calculations.
• * The choice of functional significantly impacts the accuracy of LR-TDDFT for RIXS.
• * LR-TDDFT is a promising tool for advancing RIXS data interpretation.