Simulating X-ray Absorption Spectroscopy in Challenging Environments: Methodological Insights from Water-Solvated...

Area of Science:

• Computational Chemistry
• Spectroscopy
• Physical Chemistry

Background:

• X-ray absorption spectroscopy (XAS) is crucial for studying solvent-solute interactions.
• Calculating XAS spectra in solvated systems is computationally challenging due to correlation and solvation effects.

Purpose of the Study:

• To develop and validate a computational procedure for XAS modeling in solvated systems.
• To assess the performance of explicit embedding models for XAS calculations.
• To investigate water-solvated ammonia and ammonium systems.

Main Methods:

• Linear-response time-dependent density functional theory (LR-TDDFT) calculations.
• Investigation of polarizable embedding (PE) models, including polarizable density embedding (PDE) and extended polarizable density embedding (XPDE).
• Application to water-solvated ammonia and ammonium systems.

Main Results:

• Extended polarizable embedding (XPDE) offers a robust improvement over polarizable density embedding (PDE).
• The LR-TDDFT approach with XPDE accurately describes XAS spectra of solvated ammonia and ammonium.
• The study challenges the notion that LR-TDDFT is inadequate for such systems.

Conclusions:

• A reliable computational procedure for XAS modeling in solvated systems is established.
• XPDE is an effective method for capturing solvent-solute interactions in XAS.
• LR-TDDFT can accurately predict XAS spectra for solvated molecules like ammonia and ammonium.