Theoretical study of<i>K</i>-shell excitations in formaldehyde

Trofimov, A. B.; Moskovskaya, T. É.; Gromov, Evgeniy V.; Köppel, Horst; Schirmer, J.

doi:10.1103/physreva.64.022504

Cited by 20 publications

(29 citation statements)

References 40 publications

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“…This is due to the larger displacement of the equilibrium distance of the CO bond predicted at the ADC(2) level of theory (1.280 Å in the C 1s → π * state). 60 On the other side, the displacement of the CH stretching is pretty similar: in the excited state, it is 1.02 Å according to our calculations and 1.03 Å in Trofimov's model. Our calculations accurately reproduce the spacings of the vibronic bands, thanks to the fact that the AH model explicitly accounts for the large frequency changes undergone by CO and CH stretching (see Table II) and for the Duschinsky mixings.…”

Section: Vibronic Structure Of the Bandssupporting

confidence: 58%

“…Accounting for the differences of the energy Hessians of the initial and final states of the transitions introduces frequency changes and Duschinsky mixings that remarkably improve the spacings of the main vibronic bands, although for the O 1s → 3s state they are still too large probably due to important anharmonic effects. Although we neglect interstate electronic couplings, which according to Trofimov et al 58,60,61 have some moderate effects on the spectral shapes, most of the inaccuracies of our computed spectra can be traced back to the underestimation of the elongation of the CO bond in the excited states. This indicates that for accurate vibronic line shapes of these core-excitations inclusion of the effect of triple excitations scheme may be necessary.…”

Section: Article Scitationorg/journal/jcpmentioning

confidence: 99%

“…This, however, goes beyond the present work that focuses on the assessment of the performance of the practical CCSD approach. Trofimov et al 60 explored the effect on the spectral shape of a coupling, promoted by the ν 4 out-of-plane bending motion, between C 1s → π * and C 1s → 3s states, lying ∼4.6 eV above the lower one. They adopted a linear vibronic coupling (LVC) model parameterized with ADC (2) and MRCI (multireference configuration interaction) data, while the interstate coupling was fitted to reproduce a double-well profile of C 1s → π * along ν 4 mode, predicted with ROHF calculations.…”

Section: Vibronic Structure Of the Bandsmentioning

confidence: 99%

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Coupled cluster study of the x-ray absorption spectra of formaldehyde derivatives at the oxygen, carbon, and fluorine K-edges

Frati

Groot

Cerezo

et al. 2019

The Journal of Chemical Physics

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Section: Vibronic Structure Of the Bandssupporting

confidence: 58%

Section: Article Scitationorg/journal/jcpmentioning

confidence: 99%

Section: Vibronic Structure Of the Bandsmentioning

confidence: 99%

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Coupled cluster study of the x-ray absorption spectra of formaldehyde derivatives at the oxygen, carbon, and fluorine K-edges

Frati

Groot

Cerezo

et al. 2019

The Journal of Chemical Physics

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“…As a large amount of energy is needed to promote an electron from the 1s core‐level to the lowest unoccupied molecular orbital (LUMO) region, the resulting core hole leads to a strong localized spatial contraction of the electronic wavefunction, which can be understood as orbital relaxation. Within the CVS‐ADC(2) method, these relaxation effects are included indirectly by means of double excitations, thus CVS‐ADC(2)‐x yields excellent results for core‐excited states, as has been demonstrated previously . Our new implementation of CVS‐ADC(2) in the adcman program features a fully parallelized code for the calculation of closed‐shell molecules using restricted Hartree–Fock (HF) molecular orbitals (MOs).…”

Section: Introductionmentioning

confidence: 86%

Calculating core‐level excitations and x‐ray absorption spectra of medium‐sized closed‐shell molecules with the algebraic‐diagrammatic construction scheme for the polarization propagator

2014

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Core-level excitations are generated by absorption of high-energy radiation such as X-rays. To describe these energetically high-lying excited states theoretically, we have implemented a variant of the algebraic-diagrammatic construction scheme of second-order ADC(2) by applying the core-valence separation (CVS) approximation to the ADC(2) working equations. Besides excitation energies, the CVS-ADC(2) method also provides access to properties of core-excited states, thereby allowing for the calculation of X-ray absorption spectra. To demonstrate the potential of our implementation of CVS-ADC(2), we have chosen medium-sized molecules as examples that have either biological importance or find application in organic electronics. The calculated results of CVS-ADC(2) are compared with standard TD-DFT/B3LYP values and experimental data. In particular, the extended variant, CVS-ADC(2)-x, provides the most accurate results, and the agreement between the calculated values and experiment is remarkable.

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“…7,42,43 Besides the inclusion of diffuse functions, the use of cartesian instead of pure basis functions might be a possibility to significantly improve the results. 48,49 Furthermore, the treatment of electron correlation within the ADC scheme as a post Hartree-Fock (HF) method can be systematically enhanced by going to higher order of perturbation theory. For valence-excited states, the standard ADC(3) approach 50 provides errors in excitation energies of 0.12 ± 0.28 eV, while the strict and extended ADC(2) variants exhibit an accuracy of 0.22 ± 0.38 eV and −0.70 ± 0.37 eV, respectively.…”

Section: Introductionmentioning

confidence: 99%

Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states

Wenzel

Holzer

Wormit

et al. 2015

The Journal of Chemical Physics

123

196

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The extended second order algebraic-diagrammatic construction (ADC(2)-x) scheme for the polarization operator in combination with core-valence separation (CVS) approximation is well known to be a powerful quantum chemical method for the calculation of core-excited states and the description of X-ray absorption spectra. For the first time, the implementation and results of the third order approach CVS-ADC(3) are reported. Therefore, the CVS approximation has been applied to the ADC(3) working equations and the resulting terms have been implemented efficiently in the adcman program. By treating the α and β spins separately from each other, the unrestricted variant CVS-UADC(3) for the treatment of open-shell systems has been implemented as well. The performance and accuracy of the CVS-ADC(3) method are demonstrated with respect to a set of small and middle-sized organic molecules. Therefore, the results obtained at the CVS-ADC(3) level are compared with CVS-ADC(2)-x values as well as experimental data by calculating complete basis set limits. The influence of basis sets is further investigated by employing a large set of different basis sets. Besides the accuracy of core-excitation energies and oscillator strengths, the importance of cartesian basis functions and the treatment of orbital relaxation effects are analyzed in this work as well as computational timings. It turns out that at the CVS-ADC(3) level, the results are not further improved compared to CVS-ADC(2)-x and experimental data, because the fortuitous error compensation inherent in the CVS-ADC(2)-x approach is broken. While CVS-ADC(3) overestimates the core excitation energies on average by 0.61% ± 0.31%, CVS-ADC(2)-x provides an averaged underestimation of -0.22% ± 0.12%. Eventually, the best agreement with experiments can be achieved using the CVS-ADC(2)-x method in combination with a diffuse cartesian basis set at least at the triple-ζ level.

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Theoretical study ofK-shell excitations in formaldehyde

Cited by 20 publications

References 40 publications

Coupled cluster study of the x-ray absorption spectra of formaldehyde derivatives at the oxygen, carbon, and fluorine K-edges

Coupled cluster study of the x-ray absorption spectra of formaldehyde derivatives at the oxygen, carbon, and fluorine K-edges

Calculating core‐level excitations and x‐ray absorption spectra of medium‐sized closed‐shell molecules with the algebraic‐diagrammatic construction scheme for the polarization propagator

Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states

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