Rovibrationally averaged nuclear magnetic shielding tensors calculated at the coupled-cluster level

Sundholm, Dage; Gauß, Jürgen; Schäfer, Ansgar

doi:10.1063/1.472905

Cited by 173 publications

(161 citation statements)

References 63 publications

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“…Nevertheless, as also noted by Patchkovskii et al, 19 this value of Ϸ0.3 ppm corresponds to a typical vibrational correction to the 1 H NMR chemical shifts. 34,35 In special cases the vibrational correction may even become twice as large. 36 Therefore, evaluating the performance of the SAOP potential for 1 H would require further work on the vibrational corrections.…”

Section: Resultsmentioning

confidence: 99%

Nuclear magnetic resonance chemical shifts with the statistical average of orbital-dependent model potentials in Kohn–Sham density functional theory

Poater

Lenthe

Baerends

2003

The Journal of Chemical Physics

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In this paper, an orbital-dependent Kohn-Sham exchange-correlation potential, the so-called statistical average of ͑model͒ orbital potentials, is applied to the calculation of nuclear magnetic resonance chemical shifts of a series of simple molecules containing H, C, N, O, and F. It is shown that the use of this model potential leads to isotropic chemical shifts which are substantially improved over both local and gradient-corrected functionals, especially for nitrogen and oxygen atoms. This improvement in the chemical shift calculations can be attributed to the increase in the gap between highest occupied and lowest unoccupied orbitals, thus correcting the excessively large paramagnetic contributions, which have been identified to give deficient chemical shifts with both the local-density approximation and with gradient-corrected functionals. This is in keeping with the improvement by the statitical average of orbital model potentials for response properties in general and for excitation energies in particular. The present results are comparable in accuracy to those previously reported with self-interaction corrected functionals by Patchovskii et al., but still inferior to those obtained with accurate Kohn-Sham potentials by Wilson and Tozer. However, the present approach is computationally expedient and routinely applicable to all systems, requiring virtually the same computational effort as local-density and generalized-gradient calculations.

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Section: Resultsmentioning

confidence: 99%

Nuclear magnetic resonance chemical shifts with the statistical average of orbital-dependent model potentials in Kohn–Sham density functional theory

Poater

Lenthe

Baerends

2003

The Journal of Chemical Physics

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“…According to the results of the current work, in the cc-pVQZ basis set the CCSDT-GIAO estimate for iso ( 13 C) in ethyne is 0.31 ppm lower than its CCSD(T)-GIAO counterpart. While this is a change in the right direction, at this stage it is not possible to predict whether the use of CCSDT-GIAO rather than CCSD(T)-GIAO throughout, within a very large basis set, plus a thermal correction, [30] would be sufficient to eliminate the remaining difference between the experimental and theoretical values.…”

Section: Giao Ccsd(t)-giao Casscf-giao Mp2-giao and Hf-giao Methodmentioning

confidence: 99%

Magnetic Shielding Studies of C₂ and C₂H₂ Support Higher than Triple Bond Multiplicity in C₂

Karadakov

Kirsopp

2017

Chemistry A European J

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The carbon-carbon bonds in the ground states of C 2 and C 2 H 2 , at their equilibrium geometries, are compared by analysing the changes in the off-nucleus magnetic shielding tensor within the space surrounding each of these molecules. A wide range of quantum-chemical approaches, including full-valence CASSCF-GIAO, CCSD(T)-GIAO and CCSDT-GIAO, all with the cc-pVQZ basis set, as well as HF-GIAO and MP2-GIAO, with the cc-pVQZ, cc-pV5Z and cc-pV6Z basis sets, show that the surroundings of the carbon-carbon bond in C 2 are more shielded than those of the carbon-carbon bond in C 2 H 2 . The additional shielding of the carbon-carbon bond in C 2 is found to be due to a larger paramagnetic contribution to component of the shielding tensor which is perpendicular to the molecular axis. The analysis of the off-nucleus shielding data indicates that the carbon-carbon bond in C 2 is "bulkier" and, therefore, of a higher multiplicity, but weaker than the corresponding bond in C 2 H 2 . According to the results of the shielding calculations, the carbon nuclei in C 2 should be much more shielded than those in C 2 H 2 , with 13 C isotropic magnetic shieldings in the ca. 224-227 ppm and ca. 123-125 ppm ranges for C 2 and C 2 H 2 , respectively.

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“…13 The most important are (i) the contribution of rovibrational corrections and averaging, which have been determined for only a few systems, 10,14 and (ii) the contribution of intermolecular interactions, or, more generally speaking, solvent effects. The influence of these two factors is fairly constant for similar molecular systems under similar external conditions.…”

Section: Introductionmentioning

confidence: 99%

^14,15N NMR Shielding Constants from Density Functional Theory

2003

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The prediction of nuclear magnetic resonance (NMR) shielding parameters for the N atom represents a particularly difficult task for most of the Hartree-Fock (HF)-based or density functional theory (DFT)-based methodologies. In fact, for some molecular systems, the effect of the presence of a lone pair and multiple bonds on the N atom makes the use of higher correlated methods absolutely necessary to obtain accurate results. In this article, we present an extensive study covering almost the entire spectrum of nitrogen shielding, from +400 to -50 ppm. The sum-over-states density functional perturbation theory (SOS-DFPT) has been used to calculate the shielding constant of 132 different N atoms. The potential of the various SOS-DFPT local approximations has been assessed through the comparison of N atoms that belong to similar molecular systems to experimental data. This procedure allows us to determine the margin of error to be considered in the SOS-DFPT calculation of the isotropic shieldings for each type of N atom.

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Rovibrationally averaged nuclear magnetic shielding tensors calculated at the coupled-cluster level

Cited by 173 publications

References 63 publications

Nuclear magnetic resonance chemical shifts with the statistical average of orbital-dependent model potentials in Kohn–Sham density functional theory

Nuclear magnetic resonance chemical shifts with the statistical average of orbital-dependent model potentials in Kohn–Sham density functional theory

Magnetic Shielding Studies of C₂ and C₂H₂ Support Higher than Triple Bond Multiplicity in C₂

^14,15N NMR Shielding Constants from Density Functional Theory

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Rovibrationally averaged nuclear magnetic shielding tensors calculated at the coupled-cluster level

Cited by 173 publications

References 63 publications

Nuclear magnetic resonance chemical shifts with the statistical average of orbital-dependent model potentials in Kohn–Sham density functional theory

Nuclear magnetic resonance chemical shifts with the statistical average of orbital-dependent model potentials in Kohn–Sham density functional theory

Magnetic Shielding Studies of C2 and C2H2 Support Higher than Triple Bond Multiplicity in C2

14,15N NMR Shielding Constants from Density Functional Theory

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Product

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Magnetic Shielding Studies of C₂ and C₂H₂ Support Higher than Triple Bond Multiplicity in C₂

^14,15N NMR Shielding Constants from Density Functional Theory