Assignment of vibrational states within configuration interaction calculations

Mathea, Tina; Rauhut, Guntram

doi:10.1063/5.0009732

Cited by 17 publications

(32 citation statements)

References 43 publications

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“…For example, the CH‐stretchings of fluoroethane show strong resonance/multi‐mode character which, inter alia, lead to large configuration spaces. This selection also takes different point groups into account, that is, Abelian versus non‐Abelian point groups are considered, which behave differently with respect to the handling of a real‐based configuration space (see Reference [26]). This, in addition, allows to consider different situations regarding the exploitation of symmetry properties.…”

Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

“…For the subsequent VCI calculations, an iterative procedure has been used (Note: For additional and detailed information concerning our VCI algorithm, we refer to References [2,25,26]. ).…”

Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

“…Within this configuration selection process, the correlation space is iteratively increased by employing Equation () until convergence of the state energy is reached. Using the algorithm described in Reference [26], the eigenstate having the largest overlap integral with the multi‐dimensional harmonic wavefunction is chosen to be the reference state in Equation (). In order to determine the intermediate VCI wavefunctions within these iterations, we use an iterative eigenvalue solver based on the RACE‐algorithm, 14 which has been shown to outperform the commonly used Jacobi–Davidson algorithm.…”

Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

“…In order to determine the intermediate VCI wavefunctions within these iterations, we use an iterative eigenvalue solver based on the RACE‐algorithm, 14 which has been shown to outperform the commonly used Jacobi–Davidson algorithm. In order to guarantee that the state of interest is tracked properly during the iterations of configuration selection, physically meaningful startvectors are needed 26 …”

Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

“…For Abelian systems and rectilinear normal coordinates, a single Hartree product is used, otherwise meaningful linear combinations representing all physically relevant information are employed, that is,

∣ Ψ_{A}^{(1)} true〉 goodbreak= ({, \begin{array}{c} left & ∣ Φ_{0} true〉 for Abelian systems \\ \sum_{n} c_{n} ∣ Φ_{n} true〉 else, normale . normalg ., non ‐ Abelian systems and / or localized normal coordinates \end{array})

with the coefficients

c_{n}

describing meaningful linear combinations of real‐valued configurations covering additional quantum numbers as, for example, the l ‐quantum number. For further details, we refer to Reference [26]. Subsequently, Equation () is utilized for the configuration selection process.…”

Section: Prediagonalization Of Subspacesmentioning

confidence: 99%

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Advances in vibrational configuration interaction theory ‐ part 1: Efficient calculation of vibrational angular momentum terms

Mathea

Rauhut

2021

J Comput Chem

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Finite basis vibrational configuration interaction theory (VCI) is a highly accurate method for the variational calculation of state energies and related properties, but suffers from fast growing computational costs in dependence of the size of the correlation space. In this series of papers, concepts and techniques will be presented, which diminish the computational demands and thus broaden the applicability of this method to larger molecules or more complex situations. This first part focuses on a highly efficient implementation of the vibrational angular momentum (VAM) terms as occurring in the Watson Hamiltonian and the prediagonalization of initial subspaces within an iterative configuration selective VCI implementation. Working equations and benchmark calculations are provided, the latter demonstrating the increased performance of the new algorithm.

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Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

“…For the subsequent VCI calculations, an iterative procedure has been used (Note: For additional and detailed information concerning our VCI algorithm, we refer to References [2,25,26]. ).…”

Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

Section: Computational Details and Benchmark Systemsmentioning

confidence: 99%

∣ Ψ_{A}^{(1)} true〉 goodbreak= ({, \begin{array}{c} left & ∣ Φ_{0} true〉 for Abelian systems \\ \sum_{n} c_{n} ∣ Φ_{n} true〉 else, normale . normalg ., non ‐ Abelian systems and / or localized normal coordinates \end{array})

with the coefficients

c_{n}

Section: Prediagonalization Of Subspacesmentioning

confidence: 99%

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Advances in vibrational configuration interaction theory ‐ part 1: Efficient calculation of vibrational angular momentum terms

Mathea

Rauhut

2021

J Comput Chem

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Solving the Puzzle of the Carbonic Acid Vibrational Spectrum – an Anharmonic Story

Schlagin,

Dinu,

Bernard

et al. 2024

ChemPhysChem

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Against the general belief that carbonic acid is too unstable for synthesis, it was possible to synthesize the solid as well as gas‐phase carbonic acid. It was suggested that solid carbonic acid might exist in Earth’s upper troposphere and in the harsh environments of other solar bodies, where it undergoes a cycle of synthesis, decomposition, and dimerization. To provide spectroscopic data for probing the existence of extraterrestrial carbonic acid, matrix‐isolation infrared (MI‐IR) spectroscopy has shown to be essential. However, early assignments within the harmonic approximation using scaling factors impeded a full interpretation of the rather complex MI‐IR spectrum of H2CO3. Recently, carbonic acid was detected in the Galactic center molecular cloud and triggered new interest in the anharmonic spectrum. In this regard, we substantially reassign our Argon MI‐IR spectra relying on accurate anharmonic calculations. We calculate a four‐mode potential energy surface (PES) at the explicitly correlated coupled‐cluster theory using up to triple‐zeta basis sets, i.e., CCSD(T)‐F12/cc‐pVTZ‐F12. On this PES, we perform vibrational self‐consistent field and configuration interaction (VSCF/VCI) calculations to obtain accurate vibrational transition frequencies and resonance analysis of the fundamentals, first overtones, and combination bands.

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Advances in vibrational configuration interaction theory ‐ part 2: Fast screening of the correlation space

2021

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For larger molecules, the computational demands of configuration selective vibrational configuration interaction theory (cs-VCI) are usually dominated by the configuration selection process, which commonly is based on second order vibrational Møller-Plesset perturbation (VMP2) theory. Here we present two techniques, which lead to substantial accelerations of such calculations while retaining the desired high accuracy of the final results. The first one introduces the concept of configuration classes, which allows for a highly efficient exploitation of the analogs of the Slater-Condon rules in vibrational structure calculations with large correlation spaces. The second approach uses a VMP2 like vector for augmenting the targeted vibrational wavefunction within the selection of configurations and thus avoids any intermediate diagonalization steps. The underlying theory is outlined and benchmark calculations are provided for highly correlated vibrational states of several molecules.

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Assignment of vibrational states within configuration interaction calculations

Cited by 17 publications

References 43 publications

Advances in vibrational configuration interaction theory ‐ part 1: Efficient calculation of vibrational angular momentum terms

Advances in vibrational configuration interaction theory ‐ part 1: Efficient calculation of vibrational angular momentum terms

Solving the Puzzle of the Carbonic Acid Vibrational Spectrum – an Anharmonic Story

Advances in vibrational configuration interaction theory ‐ part 2: Fast screening of the correlation space

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