Shedding light on the enigmatic TcO₂·xH₂O structure with density functional theory and EXAFS spectroscopy
Shedding light on the enigmatic TcO₂·xH₂O structure with density functional theory and EXAFS spectroscopy
Faria Oliveira, A.; Kuc, A. B.; Heine, T.; Abram, U.; Scheinost, A.
The β-emitting 99Tc isotope is a high-yield fission product in 235U and 239Pu nuclear reactors, raising special concern in nuclear waste management due to its long half-life and the high mobility of pertechnetate (TcO4−). In the conditions of deep nuclear waste repositories, retention of Tc is achieved via biotic and abiotic reduction of TcO4− to compounds like amorphous TcO2·xH2O precipitates. It is generally accepted that these precipitates have linear (Tc(μ O)2(H2O)2)n chains, with trans H2O. Although corresponding Tc Tc and Tc O distances have been obtained from Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, this structure is largely based on analogy with other compounds. Here, we combine Density-Functional Theory with EXAFS measurements of fresh and aged samples to show that, instead, TcO2·xH2O forms zigzag chains that undergo a slow aging process whereby they combine to form longer chains and, later, a tridimensional structure that might lead to a new TcO2 polymorph.
Keywords: Chain structures; Density functional calculations; EXAFS spectroscopy; Nuclear waste management; Technetium
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
Related publications
- DOI: 10.1107/S1600577520014265 is cited by this (Id 34903) publication
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Chemistry - A European Journal 28(2022)59, e202202235
Online First (2022) DOI: 10.1002/chem.202202235
Cited 3 times in Scopus -
Lecture (Conference)
ATAS-AnXAS 2022, 17.-21.10.2022, Grenoble, France
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