Electronic Structure and Properties of Berkelium Iodates

Mark A. Silver, Samantha K. Cary, Alejandro J. Garza, Ryan E. Baumbach, Alexandra A. Arico, Gregory A. Galmin, Kuan Wen Chen, Jason A. Johnson, Jamie C. Wang, Ronald J. Clark, Alexander Chemey, Teresa M. Eaton, Matthew L. Marsh, Kevin Seidler, Shane S. Galley, Lambertus Van De Burgt, Ashley L. Gray, David E. Hobart, Kenneth Hanson, Shelley M. Van CleveFrédéric Gendron, Jochen Autschbach, Gustavo E. Scuseria, Laurent Maron, Manfred Speldrich, Paul Kögerler, Cristian Celis-Barros, Dayán Páez-Hernández, Ramiro Arratia-Pérez, Michael Ruf, Thomas E. Albrecht-Schmitt

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

The reaction of 249Bk(OH)4 with iodate under hydrothermal conditions results in the formation of Bk(IO3)3 as the major product with trace amounts of Bk(IO3)4 also crystallizing from the reaction mixture. The structure of Bk(IO3)3 consists of nine-coordinate BkIII cations that are bridged by iodate anions to yield layers that are isomorphous with those found for AmIII, CfIII, and with lanthanides that possess similar ionic radii. Bk(IO3)4 was expected to adopt the same structure as M(IO3)4 (M = Ce, Np, Pu), but instead parallels the structural chemistry of the smaller ZrIV cation. BkIII-O and BkIV-O bond lengths are shorter than anticipated and provide further support for a postcurium break in the actinide series. Photoluminescence and absorption spectra collected from single crystals of Bk(IO3)4 show evidence for doping with BkIII in these crystals. In addition to luminescence from BkIII in the Bk(IO3)4 crystals, a broad-band absorption feature is initially present that is similar to features observed in systems with intervalence charge transfer. However, the high-specific activity of 249Bk (t1/2 = 320 d) causes oxidation of BkIII and only BkIV is present after a few days with concomitant loss of both the BkIII luminescence and the broadband feature. The electronic structure of Bk(IO3)3 and Bk(IO3)4 were examined using a range of computational methods that include density functional theory both on clusters and on periodic structures, relativistic ab initio wave function calculations that incorporate spin-orbit coupling (CASSCF), and by a full-model Hamiltonian with spin-orbit coupling and Slater-Condon parameters (CONDON). Some of these methods provide evidence for an asymmetric ground state present in BkIV that does not strictly adhere to Russel-Saunders coupling and Hund's Rule even though it possesses a half-filled 5f 7 shell. Multiple factors contribute to the asymmetry that include 5f electrons being present in microstates that are not solely spin up, spin-orbit coupling induced mixing of low-lying excited states with the ground state, and covalency in the BkIV-O bonds that distributes the 5f electrons onto the ligands. These factors are absent or diminished in other f7 ions such as GdIII or CmIII.

Original languageEnglish
Pages (from-to)13361-13375
Number of pages15
JournalJournal of the American Chemical Society
Volume139
Issue number38
DOIs
StatePublished - Sep 27 2017
Externally publishedYes

Funding

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Elements Chemistry Program, under Award Numbers DE-FG02-13ER16414 (FSU), DE-SC0001136 (formerly DE-FG02-09ER16066) (FG & JA), and DE-FG02-04ER15523 (G.E.S). G.E.S. is a Welch Foundation Chair (Grant No. C-0036). The isotopes used in this research were supplied by the U.S. Department of Energy, Office of Science, by the Isotope Program in the Office of Nuclear Physics. The 249Bk was provided to Florida State University by the Isotope Development and Production for Research and Applications Program through the Radiochemical Engineering and Development Center at Oak Ridge National Laboratory. Magnetization measurements using the VSM SQUID MPMS were performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490, the State of Florida, and the U.S. Department of Energy. This research is supported in part by an appointment to the CBFO Fellowship Program (MAS), sponsored by the U.S. Department of Energy and administered by the Oak Ridge Institute for Science and Education. Jamie Wang is supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1449440.

FundersFunder number
Heavy Elements Chemistry ProgramDE-FG02-13ER16414
Office of Basic Energy Sciences
Office of Nuclear Physics
National Science Foundation
U.S. Department of Energy
Welch Foundation
Office of Science
Oak Ridge Institute for Science and Education
Fayetteville State UniversityDE-FG02-09ER16066, DE-FG02-04ER15523, DE-SC0001136
Fayetteville State University

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