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Motta LC, Autschbach J. Theoretical Evaluation of Metal-Ligand Bonding in Neptunium Compounds in Relation to 237Np Mössbauer Spectroscopy. Inorg Chem 2022; 61:13399-13412. [PMID: 35960509 DOI: 10.1021/acs.inorgchem.2c01516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 237Np Mössbauer 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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Affiliation(s)
- Laura C Motta
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000, United States
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000, United States
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Motta LC, Autschbach J. 237Np Mössbauer Isomer Shifts: A Lesson About the Balance of Static and Dynamic Electron Correlation in Heavy Element Complexes. J Chem Theory Comput 2022; 18:3483-3496. [PMID: 35594193 DOI: 10.1021/acs.jctc.2c00194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A large set of neptunium compounds with different oxidation states (III to VII) was assembled to study the Mössbauer isomer shift by wave function calculations and better understand covalency in f-elements complexes. The contact density approach was used to calculate the isomer shift using complete active space self-consistent field (CASSCF) multiconfiguration wave functions, as well as matrix product states [from Density Matrix Renormalization Group (DMRG) algorithms] for large active spaces. Dynamic correlation effects for the isomer shifts were treated via CASPT2 energy derivatives with respect to the nuclear radius. The CASSCF calculations appear to produce different orbital overlocalization errors for low and high Np oxidation states. For compounds with low Np oxidation numbers, the errors can be attributed to the overlocalization of the 5f orbitals. For the compounds with high Np oxidation numbers, the main errors arise from an overlocalization of ligand orbitals and concomitant to weak donation bonding. Attempts to mitigate the overlocalization errors with large active spaces using DMRG were only partially successful, showing that explicit treatment of dynamic correlation is necessary for accurate predictions of Mössbauer isomer shifts. The CASPT2 calculations perform very satisfactorily. For a subset of Np compounds, both static and dynamic correlation effects were substantial. A rational active space selection based on orbital entanglement diagrams proved beneficial for determining the optimal reference wave function.
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Affiliation(s)
- Laura C Motta
- Department of Chemistry, University at Buffalo State University of New York, Buffalo, New York 14260-3000, United States
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo State University of New York, Buffalo, New York 14260-3000, United States
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Thomas EL, Stegman S, Skanthakumar S, Wilson RE. Applications of Alkali Metal Hydroxide Hydrofluxes to the Synthesis of Single‐Crystal Ternary Actinide Oxides. Chemistry 2020; 26:1497-1500. [DOI: 10.1002/chem.201904677] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Evan L. Thomas
- Chemical Sciences and Engineering Division Argonne National Laboratory Argonne IL 60439 USA
| | - Samantha Stegman
- Chemical Sciences and Engineering Division Argonne National Laboratory Argonne IL 60439 USA
| | | | - Richard E. Wilson
- Chemical Sciences and Engineering Division Argonne National Laboratory Argonne IL 60439 USA
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Smith AL, Colineau E, Griveau JC, Popa K, Kauric G, Martin P, Scheinost AC, Cheetham AK, Konings RJM. A New Look at the Structural and Magnetic Properties of Potassium Neptunate K 2NpO 4 Combining XRD, XANES Spectroscopy, and Low-Temperature Heat Capacity. Inorg Chem 2017; 56:5839-5850. [PMID: 28437069 PMCID: PMC5434478 DOI: 10.1021/acs.inorgchem.7b00462] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
The
physicochemical properties of the potassium neptunate K2NpO4 have been investigated in this work using X-ray diffraction,
X-ray absorption near edge structure (XANES) spectroscopy at the Np-L3 edge, and low-temperature heat capacity measurements. A Rietveld
refinement of the crystal structure is reported for the first time.
The Np(VI) valence state has been confirmed by the XANES data, and
the absorption edge threshold of the XANES spectrum has been correlated
to the Mössbauer isomer shift value reported in the literature.
The standard entropy and heat capacity of K2NpO4 have been derived at 298.15 K from the low-temperature heat capacity
data. The latter suggest the existence of a magnetic ordering transition
around 25.9 K, most probably of the ferromagnetic type. The structure
of K2NpO4 has been refined using the Rietveld
method, and the hexavalence of neptunium has been confirmed using
XANES spectroscopy. The measured edge absorption threshold has been
correlated to the Mössbauer isomer shift reported in the literature.
In addition, low-temperature heat capacity measurements have revealed
a magnetic transition around 25.9 K, most probably of the ferromagnetic
type.
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Affiliation(s)
- Anna L Smith
- Delft University of Technology , Radiation Science & Technology Department, Nuclear Energy and Radiation Applications (NERA), Mekelweg 15, 2629 JB Delft, The Netherlands
| | - Eric Colineau
- European Commission, DG Joint Research Centre-JRC , Directorate G-Nuclear Safety & Security, Postfach 2340, D-76125 Karlsruhe, Germany
| | - Jean-Christophe Griveau
- European Commission, DG Joint Research Centre-JRC , Directorate G-Nuclear Safety & Security, Postfach 2340, D-76125 Karlsruhe, Germany
| | - Karin Popa
- European Commission, DG Joint Research Centre-JRC , Directorate G-Nuclear Safety & Security, Postfach 2340, D-76125 Karlsruhe, Germany
| | - Guilhem Kauric
- Chimie-ParisTech, ENSCP , 11 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Philippe Martin
- CEA Marcoule , CEA, DEN, DMRC/SFMA/LCC, F-30207 Bagnols-sur-Cèze Cedex, France
| | - Andreas C Scheinost
- Helmholtz Zentrum Dresden Rossendorf (HZDR) , Institute of Resource Ecology, P.O. Box 10119, 01314 Dresden, Germany
| | - Anthony K Cheetham
- Department of Materials Science and Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Rudy J M Konings
- European Commission, DG Joint Research Centre-JRC , Directorate G-Nuclear Safety & Security, Postfach 2340, D-76125 Karlsruhe, Germany
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Smith AL, Martin P, Prieur D, Scheinost AC, Raison PE, Cheetham AK, Konings RJM. Structural Properties and Charge Distribution of the Sodium Uranium, Neptunium, and Plutonium Ternary Oxides: A Combined X-ray Diffraction and XANES Study. Inorg Chem 2016; 55:1569-79. [DOI: 10.1021/acs.inorgchem.5b02476] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Anna L. Smith
- European Commission, Joint Research Centre
(JRC), Institute for Transuranium Elements (ITU), P.O. Box 2340, D-76125 Karlsruhe, Germany
- Department of Materials
Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Philippe Martin
- CEA, DEN, DEC, CEN Cadarache, 13108 St. Paul Lez Durance, France
| | - Damien Prieur
- European Commission, Joint Research Centre
(JRC), Institute for Transuranium Elements (ITU), P.O. Box 2340, D-76125 Karlsruhe, Germany
| | - Andreas C. Scheinost
- Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology, P.O.
Box 10119, 01314 Dresden, Germany
| | - Philippe E. Raison
- European Commission, Joint Research Centre
(JRC), Institute for Transuranium Elements (ITU), P.O. Box 2340, D-76125 Karlsruhe, Germany
| | - Anthony K. Cheetham
- Department of Materials
Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Rudy J. M. Konings
- European Commission, Joint Research Centre
(JRC), Institute for Transuranium Elements (ITU), P.O. Box 2340, D-76125 Karlsruhe, Germany
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