Hyper-Raman Spectra in Solution Based on the Reference Interaction Site Model Self-Consistent Field Method Coupled...

Area of Science:

• Computational Chemistry
• Spectroscopy
• Physical Chemistry

Background:

• Hyper-Raman (HR) spectroscopy provides valuable molecular information but calculating spectra in solution is challenging.
• Accurate theoretical models are needed to understand solvation effects on molecular vibrations and spectra.

Purpose of the Study:

• To develop and validate a novel computational approach for calculating hyper-Raman (HR) spectra of molecules in solution.
• To enable efficient and accurate prediction of HR spectral properties, including peak positions, shifts, and depolarization ratios.
• To provide a theoretical framework for studying solvation effects on molecular structures and spectra in condensed phases.

Main Methods:

• Combining the reference interaction site model self-consistent field method with constrained spatial electron density distribution (RISM-SCF-cSED).
• Incorporating second-order vibrational quasi-degenerate perturbation theory (VQDPT2) to model anharmonic vibrations.
• Utilizing integral equation theory to describe solvent effects.

Main Results:

• The proposed method efficiently computes HR spectra in solution with low computational cost.
• Accurate predictions of peak positions and shifts were achieved for N-methylacetamide (NMA) in various solutions.
• Calculated depolarization ratios showed strong agreement with experimental data for different vibronic modes.

Conclusions:

• The developed RISM-SCF-cSED/VQDPT2 method is a powerful tool for theoretical calculations of HR spectra in solution.
• This approach accurately captures molecular structures and solvation effects, applicable to biomolecules and peptide bonds.
• The study demonstrates the utility of the method for understanding complex molecular systems in condensed phases.