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Molecular Spectroscopy: Absorption and Emission

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Vibrational absorption spectra from vibrational coupled cluster damped linear response functions calculated using an

Bo Thomsen¹, Mikkel Bo Hansen, Peter Seidler

¹The Lundbeck Foundation Center for Theoretical Chemistry, Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark. bothomsen@chem.au.dk

The Journal of Chemical Physics

|April 3, 2012

Summary

We introduce a new method using vibrational coupled cluster (VCC) damped response functions to calculate molecular absorption spectra. This approach offers a more efficient way to determine vibrational spectra for various molecules.

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Area of Science:

Quantum chemistry
Spectroscopy
Computational physics

Background:

Vibrational coupled cluster (VCC) theory is a powerful tool for describing molecular vibrations.
Calculating molecular absorption spectra is crucial for understanding molecular properties and interactions.
Existing methods for calculating spectra can be computationally intensive.

Purpose of the Study:

To develop and implement a novel theory for vibrational coupled cluster (VCC) damped response functions.
To establish a computationally efficient method for calculating molecular absorption spectra.
To demonstrate the utility of the new method for predicting IR spectra of small organic molecules.

Main Methods:

The study employs the imaginary part of the VCC damped response function to obtain absorption spectra.
Complex VCC response equations are solved using an asymmetric matrix version of the Lanczos method.
A tridiagonal representation of the VCC response Jacobian is generated within the Lanczos space.

Main Results:

The developed method provides a direct route to calculating VCC damped response functions and absorption spectra.
Theoretical analysis and numerical tests explore the algorithm's convergence behavior.
The method is validated by comparing results with previous vibrational configuration interaction calculations.

Conclusions:

The new VCC-based damped response function method offers an efficient approach for computing molecular absorption spectra.
Calculations for oxazole, cyclopropene, and uracil demonstrate the practical applicability of the method.
This work advances computational spectroscopy by providing a robust VCC-based tool.