Selected Aspects Concerning the Efficient Calculation of Vibrational Spectra beyond the Harmonic Approximation

Oschetzki, Dominik; Neff, Michael; Meier, Patrick; Pfeiffer, Florian; Rauhut, Guntram

doi:10.5562/cca2149

Cited by 35 publications

(38 citation statements)

References 59 publications

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“…A notably larger gain is found when moving to n = 3, where oc-VCC [3] gives an order of magnitude enhancement for all states except ν 1 with a significant reduction in MAD from 0.386 to 0.0712 cm −1 . oc-VCC[3pt4] achieves <0.1 cm −1 accuracy for all states and oc-VCC [4] further boosts the accuracy down to <0.01 cm −1 . Interestingly, the improvement of oc-VCC[n] over oc-VCI[n] is also significant after n = 3; the reduction in MAD, which is moderate for n = 2 (3.23 to 1.50 cm −1 ), is drastic for n = 3 (0.781-0.0712 cm −1 ).…”

Section: B Formaldehydementioning

confidence: 99%

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Optimized coordinates in vibrational coupled cluster calculations

Thomsen

Yagi

Christiansen

2014

The Journal of Chemical Physics

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Articles you may be interested inOrbitally invariant internally contracted multireference unitary coupled cluster theory and its perturbative approximation: Theory and test calculations of second order approximation J. Chem. Phys. 137, 014108 (2012); 10.1063/1.4731634 Accurate calculation of vibrational frequencies using explicitly correlated coupled-cluster theory Accurate calculation of anharmonic vibrational frequencies of medium sized molecules using local coupled cluster methods J. Chem. Phys. 126, 134108 (2007); 10.1063/1.2718951 MRCI calculations on the helium dimer employing an interaction optimized basis setThe use of variationally optimized coordinates, which minimize the vibrational self-consistent field (VSCF) ground state energy with respect to orthogonal transformations of the coordinates, has recently been shown to improve the convergence of vibrational configuration interaction (VCI) towards the exact full VCI [K. Yagi, M. Keçeli, and S. Hirata, J. Chem. Phys. 137, 204118 (2012)]. The present paper proposes an incorporation of optimized coordinates into the vibrational coupled cluster (VCC), which has in the past been shown to outperform VCI in approximate calculations where similar restricted state spaces are employed in VCI and VCC. An embarrassingly parallel algorithm for variational optimization of coordinates for VSCF is implemented and the resulting coordinates and potentials are introduced into a VCC program. The performance of VCC in optimized coordinates (denoted oc-VCC) is examined through pilot applications to water, formaldehyde, and a series of water clusters (dimer, trimer, and hexamer) by comparing the calculated vibrational energy levels with those of the conventional VCC in normal coordinates and VCI in optimized coordinates. For water clusters, in particular, oc-VCC is found to gain orders of magnitude improvement in the accuracy, exemplifying that the combination of optimized coordinates localized to each monomer with the size-extensive VCC wave function provides a supreme description of systems consisting of weakly interacting sub-systems.

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Section: B Formaldehydementioning

confidence: 99%

“…These results clearly demonstrate the advantage of using optimized coordinates for VCC. To better understand the nature of the enhanced accuracy beyond n = 3, the excitation level weights for VCI [4], VCC [4], oc-VCI [4], and VCC [4] are examined. (See Table SI in the supplementary material 52 for the whole data.)…”

Section: B Formaldehydementioning

confidence: 99%

Optimized coordinates in vibrational coupled cluster calculations

Thomsen

Yagi

Christiansen

2014

The Journal of Chemical Physics

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“…Dipole surfaces as needed for the evaluation of infrared intensities were truncated after the 2D terms and were determined at the density fitting Hartree-Fock level. We have shown quite recently that this rather crude approximation yields results, which are not only qualitatively correct, but which are in good agreement with accurate results [5]. In a subsequent step, the potential being represented by grid points was transformed to polynomials up to 8th order.…”

Section: Computational Details For the Lithium Fluoride Clustersmentioning

confidence: 65%

“…Details of this procedure are presented elsewhere. Benchmark calculations for small lithium fluoride clusters [5], i.e. Li 2 F 2 , showed that the combination of density fitting explicitly correlated local coupledcluster calculations for the 1D and 2D terms and the modeling scheme for the 3D terms results in deviations of about one wavenumber in comparison to conventional coupled-cluster calculations for the 1D, 2D and 3D terms and are thus negligible.…”

Section: Computational Details For the Lithium Fluoride Clustersmentioning

confidence: 99%

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Efficient Calculation of Multi-dimensional Potential Energy Surfaces of Molecules and Molecular Clusters

Neff

Oschetzki

Yudin

et al. 2013

High Performance Computing in Science and Engineering ‘13

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Highly accurate multi-dimensional potential energy surfaces have been computed in a fully automated fashion using newly implemented grid computing capabilities, which allow for the use of an unlimited number of cores. This new feature, which has been interfaced to our potential energy surface generator, allows for the accurate investigation of molecular systems, which are significantly larger than reported in the recent literature. Multi-dimensional potential energy surfaces at the coupled-cluster level were generated for systems of up to 16 atoms, which were used to compute accurate anharmonic vibrational spectra, which can directly be compared with experimental data.

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Vibrational Spectrum and Gas‐Phase Structure of Disulfur Dinitride (S₂N₂)

Perrin

Antognini

Zeng

et al. 2014

Chemistry A European J

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Gas-phase FTIR spectra of the ν6 (B-type) and the ν4 (C-type) fundamental bands of S2 N2 (D2h ) were recorded with a resolution of ≤0.004 cm(-1) and the vibrational spectrum of S2 N2 (D2h ) in solid Ar has been revisited. All IR-active fundamentals and four combination bands were assigned in excellent agreement with calculated values from anharmonic VPT2 and VCI theory based on (explicitly correlated) coupled-cluster surfaces. Accurate experimental vibrational ground- and excited-state rotational constants of (32) S2 (14) N2 are obtained from a rovibrational analysis of the ν6 and ν4 fundamental bands, and precise zero-point average rz (Rz (SN)=1.647694(95) Å, αz (NSN)=91.1125(33)°) and semi-experimental equilibrium structures (Re (SN)=1.64182(33) Å, αe (NSN)=91.0716(93)°) of S2 N2 have been established. These are compared to the solid-state structure of S2 N2 and structural properties of related sulfur nitrogen compounds and to results of ab initio structure calculations.

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Selected Aspects Concerning the Efficient Calculation of Vibrational Spectra beyond the Harmonic Approximation

Cited by 35 publications

References 59 publications

Optimized coordinates in vibrational coupled cluster calculations

Optimized coordinates in vibrational coupled cluster calculations

Efficient Calculation of Multi-dimensional Potential Energy Surfaces of Molecules and Molecular Clusters

Vibrational Spectrum and Gas‐Phase Structure of Disulfur Dinitride (S₂N₂)

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Selected Aspects Concerning the Efficient Calculation of Vibrational Spectra beyond the Harmonic Approximation

Cited by 35 publications

References 59 publications

Optimized coordinates in vibrational coupled cluster calculations

Optimized coordinates in vibrational coupled cluster calculations

Efficient Calculation of Multi-dimensional Potential Energy Surfaces of Molecules and Molecular Clusters

Vibrational Spectrum and Gas‐Phase Structure of Disulfur Dinitride (S2N2)

Contact Info

Product

Resources

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Vibrational Spectrum and Gas‐Phase Structure of Disulfur Dinitride (S₂N₂)