199Hg M�ssbauer measurements on mercury alloys and Hg-fluorides

Wurtinger, W.; Kankeleit, E.

doi:10.1007/bf01435591

Cited by 15 publications

(4 citation statements)

References 30 publications

(27 reference statements)

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“…As the proportionality constant between the contact density and the isomer shift depends on the fractional nuclear charge radius

〈 Δ r^{2} 〉 = R^{2} (Δ R / R)

, the latter can be determined by comparing the experimentally measured isomer shifts with the theoretically calculated contact densities in a series of compounds of the same element. Although measured 199 Hg isomer shifts are scarce, one can attempt to derive the fractional charge radius of mercury from the isomer shifts of Hg 2 F 2 and HgF 2 measured by Wurtinger and Kankeleit . Using simple cluster models of the Hg 2 F 2 and HgF 2 crystals, which were modeled by an Hg 2 F 2 linear fragment and an HgF 4 2− tetrahedral fragment with the geometries taken from the crystallographic data, the NESC/CCSD calculations yielded for

Δ \bar{ρ}

ρ – with respect to mercury atom 86.432 e/bohr −3 (Hg 2 F 2 ) and 220.839 e/bohr −3 (HgF 2 ), respectively.…”

Section: Nesc Analytic Energy Derivativesmentioning

confidence: 99%

“…Although measured 199 Hg isomer shifts are scarce, one can attempt to derive the fractional charge radius of mercury from the isomer shifts of Hg 2 F 2 and HgF 2 measured by Wurtinger and Kankeleit. [79] Using simple cluster models of the Hg 2 F 2 and HgF 2 crystals, which were modeled by an Hg 2 F 2 linear fragment and an HgF 4 22 tetrahedral fragment with the geometries taken from the crystallographic data, the NESC/CCSD calculations yielded for Dqwith respect to mercury atom 86.432 e/bohr 23 (Hg 2 F 2 ) and 220.839 e/bohr 23 (HgF 2 ), respectively. Using these densities and the experimental M€ ossbauer isomer shift difference of 21.77 mm/s, a value hDr 2 i52:4 Á 10 23 fm 2 was obtained [80] that is in good agreement with hDr 2 i52:9 Á 10 23 fm 2 for the 199 Hg 158.4 keV E2 ctransition obtained from experimental data on muonic atoms.…”

Section: Nesc Contact Density and M€ Osbauer Isomer Shiftmentioning

confidence: 99%

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Calculation of response properties with the normalized elimination of the small component method

Filatov

Zou

Cremer

2013

Int J of Quantum Chemistry

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The normalized elimination of the small component method is a first principles two-component relativistic approach that leads to the Dirac-exact description of one-electron systems. Therefore, it is an ideal starting point for developing procedures, by which first-and second-order response properties can be routinely calculated. We present algorithms and methods for the calculation of molecular response properties such as geometries, dipole moments, hyperfine structure constants, vibrational frequencies and force constants, electric polarizabilities, infrared intensities and so forth. The described formalisms are applied to molecules containing mercury and other heavy elements, which require a relativistic treatment. Perspectives for the future development and application of Dirac-exact methods are outlined.

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“…As the proportionality constant between the contact density and the isomer shift depends on the fractional nuclear charge radius

〈 Δ r^{2} 〉 = R^{2} (Δ R / R)

Δ \bar{ρ}

ρ – with respect to mercury atom 86.432 e/bohr −3 (Hg 2 F 2 ) and 220.839 e/bohr −3 (HgF 2 ), respectively.…”

Section: Nesc Analytic Energy Derivativesmentioning

confidence: 99%

Section: Nesc Contact Density and M€ Osbauer Isomer Shiftmentioning

confidence: 99%

Calculation of response properties with the normalized elimination of the small component method

Filatov

Zou

Cremer

2013

Int J of Quantum Chemistry

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“…Although tin and especially iron nuclei are the most prominent Mössbauer nuclei in practice, we focus here on mercury, which is also Mössbauer active but for which there are much less experimental data available [26][27][28][29][30][31] (see Refs. [32][33][34] for additional spectroscopic properties of Hg in mercury compounds).…”

Section: Introductionmentioning

confidence: 99%

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Knecht

Fux

Meer³

et al. 2011

Theor Chem Acc

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The electrostatic contribution to the Mössbauer isomer shift of mercury for the series HgF n (n = 1, 2, 4) with respect to the neutral atom has been investigated in the framework of four-and two-component relativistic theory. Replacing the integration of the electron density over the nuclear volume by the contact density (that is, the electron density at the nucleus) leads to a 10% overestimation of the isomer shift. The systematic nature of this error suggests that it can be incorporated into a correction factor, thus justifying the use of the contact density for the calculation of the Mössbauer isomer shift. The performance of a large selection of density functionals for the calculation of contact densities has been assessed by comparing with finite-field four-component relativistic coupled-cluster with single and double and perturbative triple excitations [CCSD(T)] calculations. For the absolute contact density of the mercury atom, the Density Functional Theory (DFT) calculations are in error by about 0.5%, a result that must be judged against the observation that the change in contact density along the series HgF n (n = 1, 2, 4), relevant for the isomer shift, is on the order of 50 ppm with respect to absolute densities. Contrary to previous studies of the 57 Fe isomer shift (F Neese, Inorg Chim Acta 332:181, 2002), for mercury, DFT is not able to reproduce the trends in the isomer shift provided by reference data, in our case CCSD(T) calculations, notably the non-monotonous decrease in the contact density along the series HgF n (n = 1, 2, 4). Projection analysis shows the expected reduction of the 6s 1/2 population at the mercury center with an increasing number of ligands, but also brings into light an opposing effect, namely the increasing polarization of the 6s 1/2 orbital due to increasing effective charge of the mercury atom, which explains the nonmonotonous behavior of the contact density along the series. The same analysis shows increasing covalent contributions to bonding along the series with the effective charge of the mercury atom reaching a maximum of around ?2 for HgF 4 at the DFT level, far from the formal charge ?4 suggested by the oxidation state of this recently observed species. Whereas the geometries for the linear HgF 2 and square-planar HgF 4 molecules were taken from previous computational studies, we optimized the equilibrium distance of HgF at the four-component Fock-space CCSD/aug-cc-pVQZ level, giving spectroscopic constants r e = 2.007 Å and x e = 513.5 cm -1 .Dedicated to Professor Pekka Pyykkö on the occasion of his 70th birthday and published as part of the Pyykkö Festschrift Issue.Electronic supplementary material The online version of this article

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“…EFGs cannot be obtained directly from experiment, but are extracted from measured nuclear quadrupole interactions (NQIs), which are proportional to the product of the EFG and the nuclear quadrupole moment. NQIs of Hg have been measured by means of Nuclear Quadrupole Resonance (NQR), Mo¨ssbauer spectroscopy or Perturbed Angular Correlation (PAC) spectroscopy in solid HgCl 2 , 1 Hg-halide dioxanates, 2 Hg-alloys, Hg 2 F 2 3,4 as well as other solid Hg-halides, [5][6][7] Hg-mercaptides, 8,9 Hg(CH 3 ) 2 5 and various biomolecules. [10][11][12][13][14][15][16] The latter systems are of great biological importance as mercury ions may substitute native metal ions in metalloproteins and, thereby, cause toxic effects.…”

Section: Introductionmentioning

confidence: 99%

Electric field gradients in Hg compounds: Molecular orbital (MO) analysis and comparison of 4-component and 2-component (ZORA) methods

Arcisauskaite

Knecht

Sauer

et al. 2012

Phys. Chem. Chem. Phys.

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We examine the performance of Density Functional Theory (DFT) approaches based on the Zeroth-Order Regular Approximation (ZORA) Hamiltonian (with and without inclusion of spin-orbit coupling) for predictions of electric field gradients (EFGs) at the heavy atom Hg nucleus. This is achieved by comparing with benchmark DFT and CCSD-T data (Arcisauskaite et al., Phys. Chem. Chem. Phys., 2012, 14, 2651-2657) obtained from 4-component Dirac-Coulomb Hamiltonian calculations. The investigated set of molecules comprises linear HgL(2) (L = Cl, Br, I, CH(3)) and bent HgCl(2) mercury compounds as well as the trigonal planar [HgCl(3)](-) system. In 4-component calculations we used the dyall.cv3z basis set for Hg, Br, I and the cc-pCVTZ basis set for H, C, Cl, whereas in ZORA calculations we used the QZ4P basis set for all the atoms. ZORA-4 reproduces the fully relativistic 4-component DFT reference values within 6% for all studied Hg compounds and employed functionals (BH&H, BP86, PBE0), whereas scalar relativistic (SR)-ZORA-4 results show deviations of up to 15%. Compared to our 4-component CCSD-T benchmark the BH&H functional performs best at both 4-component and ZORA levels. We furthermore observe that changes in the largest component of the diagonalised EFG tensor, V(zz), of linear HgCl(2) show a slightly stronger dependence than the r(-3) scaling upon bond length r(Hg-Cl) alterations. The 4-component/BH&H V(zz) value of -9.26 a.u. for a bent HgCl(2) (∠Cl-Hg-Cl = 120°) is close to -9.60 a.u. obtained for the linear HgCl(2) structure. Thus a point charge model for EFG calculations completely fails in this case. By means of a projection analysis of molecular orbital (MO) contributions to V(zz) in terms of the atomic constituents, we conclude that this is due to the increased importance of the Hg 5d orbitals upon bending HgCl(2) compared to the linear HgCl(2) structure. Changing ligand leads to only minor changes in V(zz) (from -9.60 a.u. (HgCl(2)) to -8.85 a.u. (HgI(2)) at the 4-component/BH&H level). This appears to be due to cancellation of contributions with opposite signs to V(zz) arising from: (i) increasing electron donation from occupied ligand orbitals to the formally empty Hg 6p orbitals and (ii) an increasing bond length and a decreasing negative charge on the ligand along the series.

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199Hg M�ssbauer measurements on mercury alloys and Hg-fluorides

Cited by 15 publications

References 30 publications

Calculation of response properties with the normalized elimination of the small component method

Calculation of response properties with the normalized elimination of the small component method

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Electric field gradients in Hg compounds: Molecular orbital (MO) analysis and comparison of 4-component and 2-component (ZORA) methods

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