Abstract:A theoretical study of the relation between the relativistic formulation of the nuclear magnetic shielding and spin-rotation tensors is presented. To this end a theoretical expression of the relativistic spin-rotation tensor is formulated, considering a molecular Hamiltonian of relativistic electrons and non-relativistic nuclei. Molecular rotation effects are introduced considering the terms of the Born-Oppenheimer decomposition, which couple the electrons and nuclei dynamics. The loss of the simple relation l… Show more
“…In Ref. 6, we developed a theoretical formalism based on first order corrections to the BO approximation. 8 The zeroth order molecular wave function is expressed as the product…”
Section: A Relativistic 4-component Expression Of the Spin-rotation mentioning
confidence: 99%
“…Taking the equilibrium configuration as starting point and neglecting vibrational effects, the Hamiltonian for the nuclei is the one corresponding to a purely rotating system described by the rigid rotor Hamiltonian, 6, 11…”
Section: A Relativistic 4-component Expression Of the Spin-rotation mentioning
confidence: 99%
“…Even though 4-component relativistic theory of NMR parameters was developed several years ago, only recently the relativistic theory of the SR tensor has been treated in detail by different authors. [5][6][7] In particular our rea) Electronic mail: azua@df.uba.ar search group has developed a formal theory considering an approximation of non-relativistic nuclei and relativistic electrons, taking into account that nuclei in molecular bound states are by far much slower than the speed of light c (in the molecule center of mass system). The starting point is a molecular Hamiltonian defined entirely in the laboratory system.…”
Section: Introductionmentioning
confidence: 99%
“…6 and explicitly presented in Ref. 7, the full consistency of this approach requires to take account of the interactions between moving electrons and moving nuclei, given by the Breit electron-nucleus interaction.…”
In this work, relativistic effects on the nuclear spin-rotation (SR) tensor originated in the electronnucleus and electron-electron Breit interactions are analysed. To this end, four-component numerical calculations were carried out in model systems HX (X=H,F,Cl,Br,I). The electron-nucleus Breit interaction couples the electrons and nuclei dynamics giving rise to a purely relativistic contribution to the SR tensor. Its leading order in 1/c is of the same value as that of relativistic corrections on the usual second order expression of the SR tensor considered in previous work [I. A. Aucar, S. S. Gómez, J. I. Melo, C. G. Giribet, and M. C. Ruiz de Azúa, J. Chem. Phys. 138, 134107 (2013)], and therefore it is absolutely necessary to establish its relative importance. For the sake of completeness, the corresponding effect originating in the electron-electron Breit interaction is also considered. It is verified that in all cases these Breit interactions yield only very small corrections to the SR tensors of both the X and H nuclei in the present series of compounds. Results of the present work strongly suggest that in order to achieve experimental accuracy in the theoretical study of the SR tensor both electron-nucleus and electron-electron Breit effects can be safely neglected.
“…In Ref. 6, we developed a theoretical formalism based on first order corrections to the BO approximation. 8 The zeroth order molecular wave function is expressed as the product…”
Section: A Relativistic 4-component Expression Of the Spin-rotation mentioning
confidence: 99%
“…Taking the equilibrium configuration as starting point and neglecting vibrational effects, the Hamiltonian for the nuclei is the one corresponding to a purely rotating system described by the rigid rotor Hamiltonian, 6, 11…”
Section: A Relativistic 4-component Expression Of the Spin-rotation mentioning
confidence: 99%
“…Even though 4-component relativistic theory of NMR parameters was developed several years ago, only recently the relativistic theory of the SR tensor has been treated in detail by different authors. [5][6][7] In particular our rea) Electronic mail: azua@df.uba.ar search group has developed a formal theory considering an approximation of non-relativistic nuclei and relativistic electrons, taking into account that nuclei in molecular bound states are by far much slower than the speed of light c (in the molecule center of mass system). The starting point is a molecular Hamiltonian defined entirely in the laboratory system.…”
Section: Introductionmentioning
confidence: 99%
“…6 and explicitly presented in Ref. 7, the full consistency of this approach requires to take account of the interactions between moving electrons and moving nuclei, given by the Breit electron-nucleus interaction.…”
In this work, relativistic effects on the nuclear spin-rotation (SR) tensor originated in the electronnucleus and electron-electron Breit interactions are analysed. To this end, four-component numerical calculations were carried out in model systems HX (X=H,F,Cl,Br,I). The electron-nucleus Breit interaction couples the electrons and nuclei dynamics giving rise to a purely relativistic contribution to the SR tensor. Its leading order in 1/c is of the same value as that of relativistic corrections on the usual second order expression of the SR tensor considered in previous work [I. A. Aucar, S. S. Gómez, J. I. Melo, C. G. Giribet, and M. C. Ruiz de Azúa, J. Chem. Phys. 138, 134107 (2013)], and therefore it is absolutely necessary to establish its relative importance. For the sake of completeness, the corresponding effect originating in the electron-electron Breit interaction is also considered. It is verified that in all cases these Breit interactions yield only very small corrections to the SR tensors of both the X and H nuclei in the present series of compounds. Results of the present work strongly suggest that in order to achieve experimental accuracy in the theoretical study of the SR tensor both electron-nucleus and electron-electron Breit effects can be safely neglected.
“…In this work, the authors also addressed the correspondence between the paramagnetic shielding and the nuclear-spinmolecular-rotation coupling constant [180]. The latter point was more thoroughly investigated in a follow-up study [181]. Within the applied approximations, it was found that the analogy between the two properties does not extend into the relativistic regime.…”
This article outlines some basic concepts of relativistic quantum chemistry and recent developments of relativistic methods for the calculation of the molecular properties that define the basic parameters of magnetic resonance spectroscopic techniques, i.e. nuclear magnetic resonance shielding, indirect nuclear spin-spin coupling and electric field gradients (nuclear quadrupole coupling), as well as with electron paramagnetic resonance g-factors and electron-nucleus hyperfine coupling. Density functional theory (DFT) has been very successful in molecular property calculations, despite a number of problems related to approximations in the functionals. In particular, for heavy-element systems, the large electron count and the need for a relativistic treatment often render the application of correlated wave function ab initio methods impracticable. Selected applications of DFT in relativistic calculation of magnetic resonance parameters are reviewed.
Ab initio
calculations of NMR parameters for compounds with heavy elements require a relativistic theoretical framework. Such calculations are able to reproduce experimentally observed ‘heavy atom’ effects in NMR spectroscopy quantitatively. Electron spin‐orbit (SO) coupling is a relativistic effect that leads to the ‘normal halogen dependence’ of light atom chemical shifts in the vicinity of heavy halogens. Similar effects exist for light atoms bound to heavy transition metals or
f
‐block elements or heavy main group elements other than halogens.
J
‐coupling constants involving heavy elements may increase by several hundred percent because of relativistic effects. The tensor properties of NMR shielding and
J
‐coupling, observed routinely in solid‐state NMR, can be impacted very strongly by relativistic effects. This article discusses representative examples, provides a rationale why relativistic effects are large for atoms with high nuclear charges, and lists a selection of quantum chemistry program packages that are capable of relativistic NMR calculations.
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