Theoretical study of the nuclear spin-molecular rotation coupling for relativistic electrons and non-relativistic nuclei. II. Quantitative results in HX (X=H,F,Cl,Br,I) compounds

The Journal of Chemical Physics

Gómez

Giribet

et al. 2013

Self Cite

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.

Section: A Electron-nucleus Breit and Electron-electron Gaunt Contrimentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Taking into account that nuclei are by far much slower than electrons, this kind of terms were completely neglected in numerical calculations presented in Ref. 7.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Breit interaction effects in relativistic theory of the nuclear spin-rotation tensor

The Journal of Chemical Physics

Gómez

Giribet

et al. 2013

Self Cite

Foundations of the LRESC model for response properties and some applications

Melo

Int J of Quantum Chemistry

et al. 2017

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Accurate calculations of some response properties, like the NMR spectroscopic parameters, are quite exigent for the theoretical quantum chemistry models together with the computational codes that are written from them. They need to include a very good description of the electronic density in regions close to the nuclei. When heavy-atom containing systems are studied, those requirements become even higher. Given that relativistic effects must be included in one way or another on the calculation of response properties of heavy-atoms and heavy-atom containing molecules, different schemes were developed during the past decades to include them in as good as possible way. There are some four-component models, which include relativistic effects in a very compact way, although calculations have large time-consumption; one also needs to deal with new and unusual four-component operators. There are also two-component models, which in general may be less accurate, although their application to property calculations on medium-size and large-size molecules are feasible, and they maintain the application of usual operators. In this review, we give the fundamentals of the two-component linear response elimination of small component formalism, LRESC, together with some applications to few selected response properties.New physical insights do appear when the LRESC model is used to analyze the effect of the environment on magnetic shieldings, and when one search for the relativistic extension of well-known nonrelativistic relationships like Flygare's relation among the NMR magnetic shielding and the nuclear spin-rotation constant. A similar relationship is found for the g-tensor and the susceptibility tensor. K E Y W O R D Sg-tensor, NMR, response properties, spin-rotation tensor, two-component methods | I N TR ODU C TI ONThe strong influence of relativistic effects on atomic and molecular response properties of heavy-atom containing molecules was first shown few decades ago.[1] Pyykk€ o included relativistic effects in the calculations of NMR spectroscopic parameters by applying a relativistic model that resemble Ramsey's theory [2] and use relativistic molecular wave function of the relativistically parameterized extended H€ uckel method, REX.[3] Other more elaborated semi-empirical methods and codes were later on used to improve those first results. [4][5][6] The importance of including relativistic effects on the calculation of response properties compelled the theoretical chemists to develop new specific relativistic theories and models. Several formalisms and models appeared in the literature from that time, whose implementations gave more accurate results than that obtained using previous schemes. [7][8][9][10][11][12] We can split them into two broad groups: four-component methods and two-component methods. [12][13][14][15] Even though accurate calculations of response properties of medium-size molecules, meaning molecules containing more than 10 heavy atoms (belonging to the fourth row or below of the Periodic Ta...

Relativistic corrections of the electric field gradient in dihalogen molecules XY (X, Y = F, Cl, Br, I, At) within the linear response elimination of the small component formalism

Int J of Quantum Chemistry

Maldonado

Melo

2021

Self Cite

We analyze the performance of the linear response elimination of the small component (LRESC) scheme to describe the electric field gradient (EFG), in dihalogen molecular systems, and also to give insight of the relativistic corrections. LRESC shows a good performance, providing results close to four-component (4c) ones for molecules containing atoms belonging up to the fifth row of the Periodic Table . When heavier nuclei are involved the difference among LRESC and 4c values reaches up to 5%. The main relativistic correction represents 80% of the nonrelativistic part for the heaviest molecule. LRESC can be applied at Hartree-Fock as well as Density Functional Theory levels, therefore we also analyze correlation effects on EFG showing that relativity enhances correlation effects and both effects are not additive. As an application of LRESC method, nuclear quadrupole moment calculations of some halogen nuclei are also carried out and compared with the most recent data.