Calculation of EPR g‐Tensors with Density Functional Theory

Patchkovskii, Serguei; Schreckenbach, Georg

doi:10.1002/3527601678.ch32

Cited by 33 publications

(33 citation statements)

References 54 publications

(243 reference statements)

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“…EPR g -values describe the interaction of the molecular magnetic dipole moment with the external magnetic field (molecular Zeeman effect). Following the modern philosophy of evaluating properties as derivatives of the total energy computed with some quantum mechanical method, the g -tensor is calculated as a mixed second-derivative with respect to the external magnetic field and the electron magnetic moment. − The response of the system to the external magnetic field within a DFT or Hartree−Fock framework is determined through the coupled-perturbed self-consistent field (CP−SCF) equations.…”

Section: Theorymentioning

confidence: 99%

Calculation of Solvent Shifts on Electronic g-Tensors with the Conductor-Like Screening Model (COSMO) and Its Self-Consistent Generalization to Real Solvents (Direct COSMO-RS)

Sinnecker¹,

Rajendran²,

Klamt³

et al. 2006

J. Phys. Chem. A

562

496

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The conductor-like screening model (COSMO) was used to investigate the solvent influence on electronic g-values of organic radicals. The previously studied diphenyl nitric oxide and di-tert-butyl nitric oxide radicals were taken as test cases. The calculations employed spin-unrestricted density functional theory and the BP and B3LYP density functionals. The g-tensors were calculated as mixed second derivative properties with respect to the external magnetic field and the electron magnetic moment. The first-order response of the Kohn-Sham orbitals with respect to the external magnetic field was determined through the coupled-perturbed DFT approach. The spin-orbit coupling operator was treated using an accurate multicenter spin-orbit mean-field (SOMF) approach. Provided that important hydrogen bonds are explicitly modeled by a supermolecule approach and that the basis set is sufficiently saturated, the COSMO calculations lead to accurate predictions of isotropic g-shifts with deviations of not more than 100 ppm relative to experiment. Very accurate results were obtained by employing a recently developed self-consistent modification of the COSMO method to real solvents (COSMO-RS), which we briefly introduce in this paper as direct COSMO-RS (D-COSMO-RS). This model gives isotropic g-shifts of similar high accuracy for water without using the supermolecule approach. This is an important result because it solves many of the problems associated with the supermolecule approach such as local minima and the choice of a suitable model system. Thus, the self-consistent D-COSMO-RS incorporates some specific solvation effects into continuum models, in particular it appears to successfully model the effects of hydrogen bonding. Although not yet widely validated, this opens a novel approach for the calculation of properties which so far only could be calculated by the inclusion of explicit solvent molecules in continuum solvation methods.

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Section: Theorymentioning

confidence: 99%

Calculation of Solvent Shifts on Electronic g-Tensors with the Conductor-Like Screening Model (COSMO) and Its Self-Consistent Generalization to Real Solvents (Direct COSMO-RS)

Sinnecker¹,

Rajendran²,

Klamt³

et al. 2006

J. Phys. Chem. A

562

496

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“…The computations used a modified version of the NMR-EPR ADF property program, which gives each GIAO contribution in Equation (2). [31] HOMO-NICS(0) contributions [ppm] HOMO-to-unoccupied [e] Compound NICS(0) tot Total [a] Diamagnetic [b] Gauge [c] HOMO-to-occupied (O h ) only partially offsets the other diatropic contributions. This difference between the net paratropicity of Si 6 2À and diatropicity of B 6 H 6 2À was attributed previously to the lowering of the HOMO energy from mixing with the external hydrogen orbitals in B 6 H 6 2À .…”

Section: Resultsmentioning

confidence: 99%

“…The magnetic shielding values associated with these local minima were computed at the GIAO-PW91PW91 [29] /IGLOIII [16] level employing the MAG-ReSpect code. [30] Schreckenbach's [13 g] modified version of the NMR-EPR implementation of the ADF computer code was used to analyze the separate contributions of the NICS tensor (Table 1) [31] at the equivalent PW91/triple-z valence basis set level. All NICS values are in ppm and have been computed at the unweighted heavy atom geometric centers of the cages or rings.…”

Section: Computational Detailsmentioning

confidence: 99%

Implications of Molecular Orbital Symmetries and Energies for the Electron Delocalization of Inorganic Clusters

2007

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Isostructural clusters exhibit contrasting magnetic properties when the number of electrons differs. Surprisingly, the same is true even for isoelectronic cages (e.g. O(h) B6H6(2-) is diatropic, whereas O(h) Si6(2-) is paratropic) or for those with different substitutents (e.g. T(d) B4H4 is paratropic, whereas T(d) B4F4 is diatropic). Indeed, the total nucleus-independent chemical shift (NICS) values, based on shieldings computed at cluster centers, may range considerably in magnitude and even change from diatropic (up-field shifted) to paratropic (down-field shifted). Similarly, individual dissected canonical molecular orbital contributions to the total NICS values computed at the "gauge-including atomic orbitals" (GIAO) level vary greatly. This contrasting behavior arises from molecular orbital energy differences, from the extent of orbital overlap, as well as from symmetry-based selection rules derived from group theory. Differences in magnetic properties may originate from the symmetry of the orbitals; specifically from the forbidden nature of the highest occupied molecular orbital --> lowest unoccupied molecular orbital (HOMO --> LUMO) electronic excitation weighted by the occupied-unoccupied orbital energy difference. Thus, HOMO-NICS values are generally highly paratropic if the HOMO --> LUMO rotational transition is allowed by symmetry selection rules.

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“…The reader can find details in Refs. [21][22][23][24][25][26][27] and citations to original literature provided therein.…”

Section: Hartree-fock and Kohn-sham Methods For Epr Calculationsmentioning

confidence: 99%

“…Figure 4 shows the 237 Np HFC constant for NpF6 calculated with HF theory and DFT using Eq. (22). The horizontal axis indicates a parameter used to scale the SO Hamiltonian integrals in the ground-state calculations, meaning that D 0 gives the SR limit.…”

Section: Cmentioning

confidence: 99%

Relativistic Methods for Calculating Electron Paramagnetic Resonance (EPR) Parameters

Bolvin

Autschbach

2015

Handbook of Relativistic Quantum Chemistry

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Calculation of EPR g‐Tensors with Density Functional Theory

Cited by 33 publications

References 54 publications

Calculation of Solvent Shifts on Electronic g-Tensors with the Conductor-Like Screening Model (COSMO) and Its Self-Consistent Generalization to Real Solvents (Direct COSMO-RS)

Calculation of Solvent Shifts on Electronic g-Tensors with the Conductor-Like Screening Model (COSMO) and Its Self-Consistent Generalization to Real Solvents (Direct COSMO-RS)

Implications of Molecular Orbital Symmetries and Energies for the Electron Delocalization of Inorganic Clusters

Relativistic Methods for Calculating Electron Paramagnetic Resonance (EPR) Parameters

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