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Updated: Nov 30, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
On-the-fly ab initio semiclassical evaluation of third-order response functions for two-dimensional electronic
Tomislav Begušić1, Jiří Vaníček1
1Laboratory of Theoretical Physical Chemistry, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
We developed a new computational method for accurate two-dimensional electronic spectra, accounting for molecular vibrations and Duschinsky effects. This approach improves upon simpler models for understanding complex molecular dynamics.
Area of Science:
- Computational Chemistry
- Quantum Dynamics
- Spectroscopy
Background:
- Accurate simulation of two-dimensional electronic spectra (2DES) is crucial for understanding molecular dynamics.
- Current methods often rely on simplified models that may not capture essential vibrational effects.
Purpose of the Study:
- To develop an accurate and computationally efficient method for calculating 2DES.
- To investigate the influence of anharmonicity and the Duschinsky effect on 2DES.
Main Methods:
- Employed the single-trajectory semiclassical thawed Gaussian approximation (ST-sTGA).
- The method is exact for harmonic potentials with mode displacement, frequency changes, and Duschinsky effects.
- Partially accounts for potential energy surface anharmonicity.
Main Results:
- Tested on model Morse potentials and applied to phenol.
- Anharmonicity effects in phenol were found to be weak.
- Duschinsky rotation and mode frequency changes are critical for accurate phenol 2DES simulations.
Conclusions:
- The ST-sTGA offers an accurate and affordable approach to 2DES computation.
- Simple displaced harmonic oscillator models are insufficient for reproducing vibronic lineshapes.
- Accurate 2DES simulations require inclusion of Duschinsky effects and mode frequency changes.
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