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Vajda, Štefan; Sprouse, G. D.; Rafailovich, M.; Noé, J.W.

doi:10.1103/physrevlett.47.1230

Cited by 29 publications

(9 citation statements)

References 3 publications

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“…[2], but is within the older estimates of Q. In fact, a more recent extensive theoretical HF study for FeX2 [19] indicated that the resulting EFG is extremely sensitive to basis sets, the ground state configuration, and the Fe-X distance, so that the authors concluded that at present no reliable theoretical prediction of the quadrupole splitting for these molecules is possible.…”

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confidence: 75%

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Determination of the Nuclear Quadrupole Moment of57Fe

1995

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We determine the nuclear quadrupole moment Q of the most important Mossbauer nucleus Fe by comparing experimental quadrupole splittings with calculated electric field gradients (EFG) for a large number of different Fe compounds. These ab initio calculations are based on the linearized-augmented plane-wave band structure method. From the slope of the linear correlation between theoretical EFGs and experimental quadrupole splittings a new value of Q( 7Fe) = 0.16 b is deduced, twice as large as previously suggested.Our results should also stimulate nuclear physicists to revise nuclear structure shell model calculations of Q. PACS numbers: 76.80.+y, 71.25.pi, 71.25.TnMossbauer spectroscopy and other hyperfine interaction measurements such as nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), or perturbed angular correlation (PAC) are widely used experimental techniques that provide local information on the interaction of a nucleus with the surrounding electronic charge distribution.An interpretation of such measurements can lead to a detailed knowledge of the electronic and magnetic structure in a solid. One of the measured quantities, namely, the quadrupole splitting 50, is proportional to the product (of the principal component Vzz) of the electric field gradient (EFG) times the nuclear quadrupole moment Q. Since the EFG is directly related to the asphericity of the electron density in the vicinity of the probe nucleus, the quadrupole splittings allow the estimation of covalency or ionicity of chemical bonds in solids, provided Q is known.Although Q is a purely nuclear quantity, for some isotopes these quadrupole moments are not well known. The method presented in this Letter to determine Q(s7Fe) can also be applied to other nuclei and therefore has large implications on all the experimental techniques mentioned above. In addition, it can be used as reference for other methods determining Q, e.g. , nuclear structure shell model calculations.The Mossbauer isotope Fe is probably the most frequently used nucleus for measuring hyperfine interactions.Nevertheless, its quadrupole moment is still a matter of controversy.While for a long time Q( Fe) was believed to be in the range from 0.15 to 0.28 b, Duff, Mishra, and Das [1] found Q = 0.082 b by comparing Hartree-Fock calculations with Mossbauer measurements of FeX2 molecules (X = CI,Br) trapped in solid Ar. Subsequently, this value for Q was supported by Vajda et al. [2] using nuclear structure (shell-model) calculations of Q(5 Fe) and the known ratio of the quadrupole splittings of~4 Fe and s7Fe impurities in hcp Zn and Cd [3]. During the last decade EFG calculations for solids became available based on the full-potential-linearizedaugmented plane-wave method (LAPW). These proved to be both accurate and reliable, which has been demonstrated for various solids including ionic insulators like LisN [4], Cu20 [5], TiOz [6], several Hg (I) and (II) halides [7], (hcp) metals [8], and the high T, superconductors [9). These successful applications give us co...

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confidence: 75%

“…Subsequently, this value for Q was supported by Vajda et al [2] using nuclear structure (shell-model) calculations of Q(5 Fe) and the known ratio of the quadrupole splittings of~4 Fe and s7Fe impurities in hcp Zn and Cd [3].…”

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confidence: 81%

Determination of the Nuclear Quadrupole Moment of57Fe

1995

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“…Recently, Schwarz and co-workers 8 applied density functional theory ͑DFT͒ to a series of solid state compounds and obtained a nuclear quadrupole moment of 0.16 b for 57 Fe, in contradiction to the previously accepted value of 0.08 b. 11 The now recommended value of 0.16 b is also favored by Fanciulli et al 12 Interestingly, Su and Coppens derived a 57 Fe NQM value that lies between the two most widely used ones, i.e., 0.12͑3͒ b using Sternheimer corrected electric field gradients together with Mössbauer data. 13 Most recently state-of-theart large scale nuclear shell-model calculations gave a nuclear quadrupole moment of 0.15͑2͒ b, 14 which supports the value favored by Schwarz and co-workers.…”

Section: Introductionmentioning

confidence: 85%

Comparison of ab initio and density functional calculations of electric field gradients: The Fe57 nuclear quadrupole moment from Mössbauer data

Schwerdtfeger

Söhnel

Pernpointner

et al. 2001

The Journal of Chemical Physics

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Articles you may be interested inThe nuclear electric quadrupole moment of antimony from the molecular methodThe quadrupole moment of the 3 ∕ 2 + nuclear ground state of Au 197 from electric field gradient relativistic coupled cluster and density-functional theory of small molecules and the solid state A point-charge model for the nuclear quadrupole moment: Coupled-cluster, Dirac-Fock, Douglas-Kroll, and nonrelativistic Hartree-Fock calculations for the Cu and F electric field gradients in CuFThe difficulty in accurate determination of the nuclear quadrupole moment of the first Iϭ3/2 excited nuclear state of 57 Fe from electronic structure calculations of the iron electric field gradient combined with Mössbauer measurements of the nuclear quadrupole splitting in the isomer shift is addressed by comparing ab initio with density functional calculations for iron pentacarbonyl, Fe͑CO͒ 5 , ferrocene, Fe͑C 5 H 5 ͒ 2 , and the 5 ⌬ g electronic ground states of FeCl 2 and FeBr 2 . While the ligand field gradient tensor components change relatively little with the method applied, the iron electric field gradient is sensitive to the specific density functional used. Single reference many-body perturbation theory for electron correlation also performs poorly for the iron electric field gradient and shows extreme oscillatory behavior with a change in the order of the perturbation series. Even with larger basis sets and coupled cluster techniques a precise value for the iron electric field gradient could not be determined from electronic structure calculations due to limitations in the theoretical procedures. In order to avoid uncertainties in the measured isomer shift which enters into the nuclear quadrupole coupling constant we determined the Mössbauer spectrum of Fe͑C 5 H 5 ͒ 2 between temperatures of 4.2 and 295 K. In this range two phase transitions are observed, but the quadrupole splitting is not very dependent on the solid state structure in each phase. Solid state effects for the Fe͑CO͒ 5 are determined by comparing the iron electric field gradient of the isolated molecule with the value obtained from first principle solid state calculations at various levels of theory. These calculations show that the influence of near neighboring effects to the iron electric field gradient is small. Fully relativistic Dirac-Hartree-Fock calculations for Fe͑CO͒ 5 reveal that relativistic effects for the iron electric field gradient are small as well. Fe͑CO͒ 5 is therefore an ideal test molecule for the determination of an accurate nuclear quadrupole moment from electronic structure calculations if combined with an experimental nuclear quadrupole coupling constant. Our best estimate for the 57 Fe nuclear quadropole moment is 0.14͑2͒ barn in reasonable agreement with recent nuclear structure calculations.

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“…The Q value of the first excited state of 57 Fe has been estimated in the early days of the Mössbauer spectroscopy as lying in between +0.15 b and +0.28 b. Calculations performed later suggested Q = +0.082 b [10,11]. More sophisticated models lead to Q = +0.16 b [12,13].…”

Section: Introductionmentioning

confidence: 98%

Calibration of the isomer shift of the 14.4 keV transition of 57 Fe

2011

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With the aim of calibrating Mössbauer spectroscopic measurements, the electron contact density was calculated on the Fe nuclear position in various iron compounds. The full-potential augmented-plane waves plus local orbitals (APW+lo) method within the local-density approximation was used, considering different approximations for the exchange and correlation potential. By comparison with experimental 57 Fe Mössbauer data, the calibration constant α relating measured isomer shifts to the electron contact density was derived. An isomer shift calibration constant α = −0.25 1 a.u. 3 mm s −1 has been obtained.

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Quadrupole Moment ofFem57

Cited by 29 publications

References 3 publications

Determination of the Nuclear Quadrupole Moment of57Fe

Determination of the Nuclear Quadrupole Moment of57Fe

Comparison of ab initio and density functional calculations of electric field gradients: The Fe57 nuclear quadrupole moment from Mössbauer data

Calibration of the isomer shift of the 14.4 keV transition of 57 Fe

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