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Updated: Jul 5, 2026

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Towards fast computations of correlated vibrational wave functions: vibrational coupled cluster response excitation
Peter Seidler1, Mikkel Bo Hansen, Ove Christiansen
1The Lundbeck Foundation Center for Theoretical Chemistry and Center for Oxygen Microscopy and Imaging, Department of Chemistry, University of Aarhus, Aarhus C, Denmark. seidler@chem.au.dk
Abstract:
An efficient implementation of vibrational coupled cluster theory with two-mode excitations and a two-mode Hamiltonian is described. The algorithm is shown to scale cubically with respect to the number of modes which is identical to the scaling of the corresponding vibrational configuration interaction algorithm. This is achieved through the use of special intermediates. The same algorithm can also be used in vibrational Møller-Plesset calculations. To improve performance, screening techniques have been implemented as well. Test calculations on polyaromatic hydrocarbons with up to 264 coupled modes and model systems with up to 1140 modes are used to illustrate the various features of the algorithm.
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