Using nested tensor train contracted basis functions with group theoretical techniques to compute (ro)-vibrational spectra of molecules with non-Abelian groups

In this paper, we use nested tensor-train contractions to compute vibrational and ro-vibrational energy levels of molecules with five and six atoms. At each step, we fully exploit symmetry by using symmetry adapted basis functions obtained from an irreducible tensor method. Contracted basis function...

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Bibliographic Details
Published in:The Journal of chemical physics 2024-07, Vol.161 (4)
Main Authors: Rey, Michaël, Carrington, Tucker
Format: Article
Language:English
Subjects:
Basis functions
Coupling (molecular)
Eigenvectors
Energy levels
Group theory
Hamiltonian functions
Matrices (mathematics)
Symmetry
Tensors
Vibrational spectra
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Summary:In this paper, we use nested tensor-train contractions to compute vibrational and ro-vibrational energy levels of molecules with five and six atoms. At each step, we fully exploit symmetry by using symmetry adapted basis functions obtained from an irreducible tensor method. Contracted basis functions are determined by diagonalizing reduced dimensional Hamiltonian matrices. The size of matrices of eigenvectors, used to account for coupling between groups of coordinates, is reduced by discarding rows and columns. The size of the matrices that must be diagonalized is thus substantially reduced, making it possible to use direct eigensolvers, even for molecules with five and six atoms. The symmetry-adapted contracted vibrational basis functions have been used to compute J = 0 energy levels of the CH3CN (C3v) and J > 0 levels of CH4.
ISSN:0021-9606
1089-7690
1089-7690
DOI:10.1063/5.0219434