Structural Sampling and Solvation Models for the Simulation of Electronic Spectra: Pyrazine as a Case Study
Shota Tsuru1, Bikramjit Sharma1, Dominik Marx1
1Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Journal of Chemical Theory and Computation
|March 27, 2023
Summary
Comparing sampling methods for pyrazine spectra, this study finds Wigner and Maxwell-Boltzmann samplings agree in the gas phase. For aqueous solutions, continuum solvation is crucial for accurate UV-vis absorption spectra convergence.
Area of Science:
- Computational Chemistry
- Spectroscopy
Background:
- Accurate spectral predictions require careful consideration of sampling methods and solvation models.
- Pyrazine serves as a model system for studying these effects in both gas and solution phases.
Purpose of the Study:
- To investigate the impact of sampling methods (Maxwell-Boltzmann vs. Wigner) on gas-phase spectra.
- To evaluate the convergence of UV-vis absorption spectra in aqueous solution using various solvation models (microsolvation, continuum, hybrid).
Main Methods:
- Calculation of static and time-resolved X-ray absorption spectra (XAS) and UV-vis absorption spectra for pyrazine.
- Comparison of Maxwell-Boltzmann and Wigner sampling techniques in the gas phase.
- Systematic investigation of spectral convergence with increasing explicit solvent shells in aqueous solution, with and without continuum solvation models.
Main Results:
- Gas-phase static and time-resolved XAS, along with UV-vis spectra, show good agreement between Wigner and Maxwell-Boltzmann sampling.
- In aqueous solution, UV-vis spectra converge rapidly for the lowest energy bands with explicit solvent shells.
- Higher-lying excitations in microsolvated clusters without continuum solvation exhibit unphysical charge-transfer excitations.
Conclusions:
- Wigner and Maxwell-Boltzmann sampling methods yield comparable results for pyrazine's gas-phase spectra.
- Accurate computation of higher-lying UV-vis absorption bands in aqueous solution necessitates the inclusion of continuum solvation models for microsolvated systems.
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