Vibrational heat-bath configuration interaction
Jonathan H Fetherolf1, Timothy C Berkelbach1
1Department of Chemistry, Columbia University, New York, New York 10027, USA.
The Journal of Chemical Physics
|February 20, 2021
Summary
We developed vibrational heat-bath configuration interaction (VHCI), an accurate and efficient method for calculating vibrational energy levels in complex molecules. VHCI provides highly accurate vibrational spectra with low computational cost.
Area of Science:
- Quantum Chemistry
- Computational Spectroscopy
- Molecular Vibrations
Background:
- Calculating vibrational eigenstates of anharmonic systems is computationally demanding.
- Existing methods often struggle with accuracy or efficiency for large molecular systems.
Purpose of the Study:
- Introduce vibrational heat-bath configuration interaction (VHCI) as a novel method.
- Achieve accurate and efficient calculation of vibrational eigenstates for anharmonic systems.
Main Methods:
- VHCI is a selected configuration interaction (CI) approach.
- Utilizes anharmonic force constants for basis state selection.
- Incorporates screened second-order perturbation theory and extrapolation for energy estimates.
Main Results:
- VHCI was benchmarked on four molecules (12-48 degrees of freedom).
- Used anharmonic potential energy surfaces truncated at fourth and sixth orders.
- Achieved sub-wavenumber accuracy for tens to hundreds of vibrational states.
Conclusions:
- VHCI offers a significant improvement over existing methods.
- Provides accurate vibrational spectra at low computational cost.
- Enables efficient study of anharmonic molecular vibrations.
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