Review of Elementary Electron Spin Resonance

Harriman, John E.

doi:10.1016/b978-0-12-326350-6.50006-1

Cited by 62 publications

(109 citation statements)

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“…In the Pnma space group discussed here, these are the same operations summarised in eq. 4 [43,44]. Consider for instance the g-tensor of site I in Figure 1b and its relation with those of the other sites: because of the operations given above, when expressed with respect to the same reference frame, such as the unit-cell frame, the g-shift tensors of sites I − IV are found to be:…”

Section: A Analysis Of the G-tensor In Solidsmentioning

confidence: 99%

DFT investigation of the effect of spin-orbit coupling on the NMR shifts in paramagnetic solids

et al. 2017

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Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool for studying the structural and electronic properties of paramagnetic solids. However, the interpretation of paramagnetic NMR spectra is often challenging as a result of the interactions of unpaired electrons with the nuclear spins of interest. In this work, we extend the formalism of the paramagnetic NMR shielding in the presence of spin-orbit coupling towards solid systems with multiple paramagnetic centres. We demonstrate how the single-ion Electron Paramagnetic Resonance (EPR) g-tensor is defined and calculated in periodic paramagnetic solids. We then calculate the hyperfine tensor and the g-tensor with density functional theory (DFT) to show the validity of the presented model and we further demonstrate how these interactions can be combined to give the overall paramagnetic shielding tensor, σ s . The method is applied to a series of olivine-type LiTMPO4 materials (with TM=Mn, Fe, Co and Ni) and the corresponding 7 Li and 31 P NMR spectra are simulated. We analyse the effects of spin-orbit coupling and of the electron-nuclear magnetic interactions on the calculated NMR parameters. A detailed comparison is presented between contact and dipolar interactions across the LiTMPO4 series, in which the magnitudes and signs of the non-relativistic and relativistic components of the overall isotropic shift and shift anisotropy are computed and rationalized.

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Section: A Analysis Of the G-tensor In Solidsmentioning

confidence: 99%

DFT investigation of the effect of spin-orbit coupling on the NMR shifts in paramagnetic solids

et al. 2017

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“…co(seacacen) ! co(sacsac) 2 . Such a trend is not observed experimentally, which confirms the above remark about the inaccuracy of the experimental determination of the A-tensor.…”

Section: The A-tensormentioning

confidence: 99%

“…It can also provide some information about the energy levels of complexes. Extraction of these informations from experimental spectra is however not always straightforward, quantum-chemical calculations are therefore needed [2]. Calculations of the g-and A-tensors within traditional ab initio approaches require sophisticated treatment of the electron correlation and large basis sets, which is computationally demanding [3].…”

Section: Introductionmentioning

confidence: 99%

Accurate predictions of the EPR parameters in planar cobalt(II) complexes by hybrid density functional theory

Zbiri

2006

Inorganica Chimica Acta

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The hybrid density functional theory is applied to calculate the electron paramagnetic resonance parameters, i.e, the g-and A-tensors of some planar Cobalt(II) complexes with a C 2v symmetry. Calculations were done for four systems: Co(acacen), Co(tacacen), Co(seacacen) and Co(sacsac) 2 . The following hybrid functionals were employed: B3LYP, B3PW91, mPW1PW91 and PBE0. The expected large deviation of the g-and A-tensors is well reproduced, and is in very good agreement with the experimental observations. Comparative study shows that the PBE0 hybrid model yields the best agreement with experimental data.

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“…The tensors A I are the hyperfine parameters (a PAW based theory for its calculation has been described elsewhere by Van de Walle and Blöchl [1,3]), and the tensor g is the EPR g tensor. In order to calculate the g tensor we start from the electronic Hamiltonian which includes terms up to order a 3 , in the presence of a constant external magnetic field B [7,11]:…”

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confidence: 99%

First-Principles Theory of the EPRgTensor in Solids: Defects in Quartz

Pickard¹,

2002

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A theory for the reliable prediction of the EPR g tensor for paramagnetic defects in solids is presented. It is based on density functional theory and on the gauge including projector augmented wave approach to the calculation of all-electron magnetic response. The method is validated by comparison with existing quantum chemical and experimental data for a selection of diatomic radicals. We then perform the first prediction of EPR g tensors in the solid state and find the results to be in excellent agreement with experiment for the E 0 1 and substitutional phosphorus defect centers in quartz. DOI: 10.1103/PhysRevLett.88.086403 PACS numbers: 71.15. -m, 61.72.Bb, 76.30. -v Electron paramagnetic resonance (EPR), also known as electron spin resonance, is the most powerful spectroscopic technique for the study of paramagnetic defects in solids. Indeed, defect centers are often named directly after their EPR spectra. Applications of EPR extend to any situation where there are unpaired electrons, including the understanding of reactions involving free radicals in both biological and chemical contexts or the study of the structure and spin state of transition metal complexes.EPR spectra of spin 1͞2 centers are made up of two contributions: (i) the hyperfine parameters, which can be computed from the ground state spin density, and have been used to connect theoretical studies of defects to available experimental data [1 -6], and (ii) the g tensor. Only recently have there been attempts to calculate the g tensor in molecules from first principles using density functional theory (DFT) [7,8]. However, these approaches are valid only for finite systems and, thus, are not useful for the calculation of the g tensor for paramagnetic defects in solids, except possibly within a cluster approximation. In the absence of a predictive scheme, experimentally determined g tensors are, of necessity, interpreted in terms of their symmetry alone, leaving any remaining information unexploited. A reliable, first-principles approach to the prediction of g tensors in solids, in combination with structural and energetic calculations, would access this information, and could be used for an unequivocal discrimination between competing microscopic models proposed for defect centers. In this Letter we describe an approach for the calculation of the g tensor in extended systems, using periodic boundary conditions and supercells.In a previous paper [9] we have shown how to compute the all-electron magnetic linear response, in finite and extended systems, using DFT and pseudopotentials. To achieve this we introduced the gauge including projector augmented wave (GIPAW) method, which is an extension of Blöchl's projector augmented wave (PAW) method [10]. In Ref.[9], we used GIPAW to compute the NMR chemical shifts in molecules and solids. Here we apply the GIPAW approach to the first-principles prediction of EPR g tensors for paramagnetic defects in solids. We validate our theory and implementation for diatomic radicals, for which both all-electron...

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Review of Elementary Electron Spin Resonance

Cited by 62 publications

References 0 publications

DFT investigation of the effect of spin-orbit coupling on the NMR shifts in paramagnetic solids

DFT investigation of the effect of spin-orbit coupling on the NMR shifts in paramagnetic solids

Accurate predictions of the EPR parameters in planar cobalt(II) complexes by hybrid density functional theory

First-Principles Theory of the EPRgTensor in Solids: Defects in Quartz

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