Mössbauer spectroscopy of neptunyl species

Kalvius, G. M.; Dunlap, B. D.; Asch, L.; Weigel, F.

doi:10.1016/j.jssc.2004.07.025

Cited by 11 publications

(17 citation statements)

References 13 publications

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“…The evidence for the participation of the 6p shell in the U−O bond gave rise to the suggestion that the resulting anisotropy of the electron density in this shell, associated with a partial hole of ∼0.33e - in the 6p z orbital, might be responsible for the electric field gradient (EFG) at the actinide nucleus. This property has been measured by Mössbauer spectroscopy , in compounds containing 237 NpO 2 2+ and 234,236,238 UO 2 2+ . For RbUO 2 (NO 3 ) 3 the axial component of the EFG is +8.14 × 10 18 V cm -2 …”

Section: Theoretical Studiesmentioning

confidence: 99%

Electronic Structure and Bonding in Actinyl Ions and their Analogs

2007

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Section: Theoretical Studiesmentioning

confidence: 99%

Electronic Structure and Bonding in Actinyl Ions and their Analogs

2007

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“…Np(VII) is indeed found in an isomer shift range −60 < δ IS < −78 mm s –1 according to the correlation diagram in the Supporting Information. Its value is significantly less negative than the free ion Np 7+ value estimated to be −194 mm s –1 /NpAl 2 . This reveals large partial occupation of the bonding orbitals by the 5f and 6d electrons …”

Section: Resultsmentioning

confidence: 69%

“…Its value is significantly less negative than the free ion Np 7+ value estimated to be −194 mm s −1 /NpAl 2 . 6 This reveals large partial occupation of the bonding orbitals by the 5f and 6d electrons. 30 The measured data were fitted using a quadrupole coupling constant |e 2 qQ| of 25.9(3) mm s −1 , and an asymmetry parameter η (affecting the external line positions) of 0.43 (3).…”

Section: ■ Experimental Methodsmentioning

confidence: 94%

“…In addition, these ternary compounds containing a [Rn]5f n central ion have also attracted considerable attention because of their interesting electronic and magnetic properties. − For actinide oxide compounds, the crystal-field interaction is usually of the same order of magnitude as the spin–orbit coupling interaction and electronic repulsion, which makes the interpretation very complex. As the 5f-orbitals of the actinides have a much greater radial extension than the 4f-orbitals of the lanthanides, which are more core-like, the crystal-field interaction cannot be treated as a small perturbation of the electronic energy levels as is done for [Xe]4f n rare earths .…”

Section: Introductionmentioning

confidence: 99%

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X-ray Diffraction, Mössbauer Spectroscopy, Magnetic Susceptibility, and Specific Heat Investigations of Na₄NpO₅ and Na₅NpO₆

et al. 2015

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The hexavalent and heptavalent sodium neptunate compounds Na4NpO5 and Na5NpO6 have been investigated using X-ray powder diffraction, Mössbauer spectroscopy, magnetic susceptibility, and specific heat measurements. Na4NpO5 has tetragonal symmetry in the space group I4/m, while Na5NpO6 adopts a monoclinic unit cell in the space group C2/m. Both structures have been refined for the first time using the Rietveld method. The valence states of neptunium in these two compounds, i.e., Np(VI) and Np(VII), respectively, have been confirmed by the isomer shift values of their Mössbauer spectra. The local structural properties obtained from the X-ray refinements have also been related to the quadrupole coupling constants and asymmetry parameters determined from the Mössbauer studies. The absence of magnetic ordering has been confirmed for Na4NpO5. However, specific heat measurements at low temperatures have suggested the existence of a Schottky-type anomaly at around 7 K in this Np(VI) phase.

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“…Although 237 Np Mössbauer spectroscopy has proven to be a valuable technique for extracting chemical bonding information in Np compounds ,,− (representing early actinide complexes more generally), the isomer shifts and QS trends have proven difficult to interpret. Regarding the isomer shift, difficulties in their interpretation arise from our limited understanding of the extent of the donation bonding in the different oxidation states.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Evaluation of Metal–Ligand Bonding in Neptunium Compounds in Relation to ²³⁷Np Mössbauer Spectroscopy

Motta

Autschbach

2022

Inorg. Chem.

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The 237 Np Mossbauer isomer shift and quadrupole splitting (QS) are powerful probes for the metal−ligand bonding of neptunium, a 5f-element of vital importance in the nuclear fuel cycle. A large set of Np compounds with different oxidation states (III) to (VII) is studied to investigate, by first-principles calculations, isomer shifts and the QS trends in relation to the Np oxidation state. Natural Bond Orbital analysis reveals that in addition to donation bonding to the 5f shell, participation of the 6d and 7s neptunium shells in covalent (donation) bonding substantially impacts the isomer shifts. The isomer shift cannot be interpreted solely by the 5f shell electron count. The isomer shift for Np(II) compounds is estimated to be in the range of 31− 34 mm/s, less positive than for Np(III) compounds. For the QS, density functional calculations fail to reproduce the quadrupole splitting for some Np(VI) ionic solids. A multiconfigurational wave function approach reproduces the observed QS trends. The calculations give a semiquantitative interpretation of the trends for Np oxidation states (V) to (VII). The contrasting QS for standard and "reverse" neptunyl(VI), at the opposite extremes of the observed QS scale, arises predominantly from the different crystal environments.

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Mössbauer spectroscopy of neptunyl species

Cited by 11 publications

References 13 publications

Electronic Structure and Bonding in Actinyl Ions and their Analogs

Electronic Structure and Bonding in Actinyl Ions and their Analogs

X-ray Diffraction, Mössbauer Spectroscopy, Magnetic Susceptibility, and Specific Heat Investigations of Na₄NpO₅ and Na₅NpO₆

Theoretical Evaluation of Metal–Ligand Bonding in Neptunium Compounds in Relation to ²³⁷Np Mössbauer Spectroscopy

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Mössbauer spectroscopy of neptunyl species

Cited by 11 publications

References 13 publications

Electronic Structure and Bonding in Actinyl Ions and their Analogs

Electronic Structure and Bonding in Actinyl Ions and their Analogs

X-ray Diffraction, Mössbauer Spectroscopy, Magnetic Susceptibility, and Specific Heat Investigations of Na4NpO5 and Na5NpO6

Theoretical Evaluation of Metal–Ligand Bonding in Neptunium Compounds in Relation to 237Np Mössbauer Spectroscopy

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X-ray Diffraction, Mössbauer Spectroscopy, Magnetic Susceptibility, and Specific Heat Investigations of Na₄NpO₅ and Na₅NpO₆

Theoretical Evaluation of Metal–Ligand Bonding in Neptunium Compounds in Relation to ²³⁷Np Mössbauer Spectroscopy