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Title: Dehydration of the Uranyl Peroxide Studtite, [UO 22-O 2)(H 2O) 2]·2H 2O, Affords a Drastic Change in the Electronic Structure: A Combined X-ray Spectroscopic and Theoretical Analysis

Abstract

The dehydration of studtite, [UO 2(2-O 2)(H 2O)2]·2H 2O, to metastudtite, [UO 2(2-O 2)(H 2O) 2], uranyl peroxide minerals that are major oxidative alteration phases of UO2 under conditions of geological storage, has been studied using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. XPS of the U 4f region shows small but significant differences between studtite and metastudtite, with the 4f binding energy of studtite the highest reported for a uranyl mineral studied by this technique. Further information on the changes in the electronic structure was elucidated using U M4-edge High Energy Resolution XANES (HR-XANES) spectroscopy, which directly probes f-orbital states. The transition from the 3d to the 5f* orbital is sensitive to variations of the U=Oaxial bond length and to changes in the bond covalency. We report evidences that the covalence in the uranyl fragment decreases upon dehydration. Photoluminescence spectroscopy at near liquid helium temperatures reveals significant spectral differences between the two materials, correlating with the X-ray spectroscopy results. A theoretical investigation has been conducted on the structures of both studtite and metastudtite and benchmarked to the HR-XANES spectra. These illustrate the sensitivity of the 3d to the 5f * transition towards U=Oaxial bond variation.

Authors:
ORCiD logo [1];  [1];  [2];  [3];  [2];  [1];  [4];  [3]; ORCiD logo [2]
  1. Institute for Nuclear Waste Disposal (INE), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
  2. School of Chemistry, University of Dublin, Trinity College, College Green, Dublin 2, Ireland
  3. Institute of Energy and Climate Research, IEK-6, Nuclear Waste Management and Reactor Safety, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Strasse, 52428 Jülich, Germany; JARA High-Performance Computing, Schinkelstrasse 2, 52062 Aachen, Germany
  4. Pacific Northwest National Laboratory, MSIN K8-96, P.O. Box 999, Richland, Washington 99352, United States
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1423413
Report Number(s):
PNNL-SA-130840
Journal ID: ISSN 0020-1669; 49695; KP1704020
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 57; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Vitova, Tonya, Pidchenko, Ivan, Biswas, Saptarshi, Beridze, George, Dunne, Peter W., Schild, Dieter, Wang, Zheming, Kowalski, Piotr M., and Baker, Robert J. Dehydration of the Uranyl Peroxide Studtite, [UO2(η2-O2)(H2O)2]·2H2O, Affords a Drastic Change in the Electronic Structure: A Combined X-ray Spectroscopic and Theoretical Analysis. United States: N. p., 2018. Web. doi:10.1021/acs.inorgchem.7b02326.
Vitova, Tonya, Pidchenko, Ivan, Biswas, Saptarshi, Beridze, George, Dunne, Peter W., Schild, Dieter, Wang, Zheming, Kowalski, Piotr M., & Baker, Robert J. Dehydration of the Uranyl Peroxide Studtite, [UO2(η2-O2)(H2O)2]·2H2O, Affords a Drastic Change in the Electronic Structure: A Combined X-ray Spectroscopic and Theoretical Analysis. United States. doi:10.1021/acs.inorgchem.7b02326.
Vitova, Tonya, Pidchenko, Ivan, Biswas, Saptarshi, Beridze, George, Dunne, Peter W., Schild, Dieter, Wang, Zheming, Kowalski, Piotr M., and Baker, Robert J. Mon . "Dehydration of the Uranyl Peroxide Studtite, [UO2(η2-O2)(H2O)2]·2H2O, Affords a Drastic Change in the Electronic Structure: A Combined X-ray Spectroscopic and Theoretical Analysis". United States. doi:10.1021/acs.inorgchem.7b02326.
@article{osti_1423413,
title = {Dehydration of the Uranyl Peroxide Studtite, [UO2(η2-O2)(H2O)2]·2H2O, Affords a Drastic Change in the Electronic Structure: A Combined X-ray Spectroscopic and Theoretical Analysis},
author = {Vitova, Tonya and Pidchenko, Ivan and Biswas, Saptarshi and Beridze, George and Dunne, Peter W. and Schild, Dieter and Wang, Zheming and Kowalski, Piotr M. and Baker, Robert J.},
abstractNote = {The dehydration of studtite, [UO2(2-O2)(H2O)2]·2H2O, to metastudtite, [UO2(2-O2)(H2O)2], uranyl peroxide minerals that are major oxidative alteration phases of UO2 under conditions of geological storage, has been studied using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. XPS of the U 4f region shows small but significant differences between studtite and metastudtite, with the 4f binding energy of studtite the highest reported for a uranyl mineral studied by this technique. Further information on the changes in the electronic structure was elucidated using U M4-edge High Energy Resolution XANES (HR-XANES) spectroscopy, which directly probes f-orbital states. The transition from the 3d to the 5f* orbital is sensitive to variations of the U=Oaxial bond length and to changes in the bond covalency. We report evidences that the covalence in the uranyl fragment decreases upon dehydration. Photoluminescence spectroscopy at near liquid helium temperatures reveals significant spectral differences between the two materials, correlating with the X-ray spectroscopy results. A theoretical investigation has been conducted on the structures of both studtite and metastudtite and benchmarked to the HR-XANES spectra. These illustrate the sensitivity of the 3d to the 5f * transition towards U=Oaxial bond variation.},
doi = {10.1021/acs.inorgchem.7b02326},
journal = {Inorganic Chemistry},
number = 4,
volume = 57,
place = {United States},
year = {Mon Feb 05 00:00:00 EST 2018},
month = {Mon Feb 05 00:00:00 EST 2018}
}