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Curium is unique in the actinide series because its half-filled 5f 7 shell has lower energy than other 5f n configurations, rendering it both redox-inactive and resistant to forming chemical bonds that engage the 5f shell1–3. This is even more pronounced in gadolinium, curium’s lanthanide analogue, owing to the contraction of the 4f orbitals with respect to the 5f orbitals4. However, at high pressures metallic curium undergoes a transition from localized to itinerant 5f electrons5. This transition is accompanied by a crystal structure dictated by the magnetic interactions between curium atoms5,6. Therefore, the question arises of whether the frontier metal orbitals in curium(iii)–ligand interactions can also be modified by applying pressure, and thus be induced to form metal–ligand bonds with a degree of covalency. Here we report experimental and computational evidence for changes in the relative roles of the 5f/6d orbitals in curium–sulfur bonds in [Cm(pydtc)4]− (pydtc, pyrrolidinedithiocarbamate) at high pressures (up to 11 gigapascals). We compare these results to the spectra of [Nd(pydtc)4]− and of a Cm(iii) mellitate that possesses only curium–oxygen bonds. Compared with the changes observed in the [Cm(pydtc)4]− spectra, we observe smaller changes in the f–f transitions in the [Nd(pydtc)4]− absorption spectrum and in the f–f emission spectrum of the Cm(iii) mellitate upon pressurization, which are related to the smaller perturbation of the nature of their bonds. These results reveal that the metal orbital contributions to the curium–sulfur bonds are considerably enhanced at high pressures and that the 5f orbital involvement doubles between 0 and 11 gigapascal. Our work implies that covalency in actinides is complex even when dealing with the same ion, but it could guide the selection of ligands to study the effect of pressure on actinide compounds. Enhanced covalency is achieved for a curium complex with curium–sulfur bonds by subjecting the compound to high pressures, indicating that pressure can be used to tune covalency in actinide compounds.

β-[NH4][UF5] and [NH4][Pu3F13] have been prepared by mild hydrothermal reactions. Their single-crystal structures have been observed to offer unexpected similarities in topology. β-[NH4][UF5] (P21/...

The structural chemistry of elements relevant to the FLiBe molten salt reactor, Th, U, Np, and Zr, including Ce and Nd (as analogues for Pu and Am, respectively), have been examined using hydrothermal synthesis at 200 °C. These reactions serve to model the reaction of molten salts under hydrolysis conditions. The results show that U and Np formed

The aqueous reaction of mellitic acid (H6mell) with 242PuBr3·nH2O forms two plutonium mellitates, 242Pu2(mell)(H2O)9·H2O (Pu-1α) and 242Pu2(mell)(H2O)8·2H2O (Pu-1β). These compounds are compared to the isomorphous lanthanide mellitates with similar ionic radii via bond length analysis. Both plutonium compounds form three-dimensional metal-organic frameworks, with Pu-1α having two unique metal centers and Pu-1β having one. All plutonium metal centers exhibit nine-coordinate geometries. Our results show metal-oxygen bond lengths for plutonium significantly shorter than those of the previously reported lanthanum and herein reported cerium analogues, consistent with the nine-coordinate ionic radii. Clear Laporte-forbidden 5f → 5f transitions are observed in the ultraviolet-visible-near-infrared spectra and are assigned to trivalent plutonium. However, there is a distinct color difference between the two plutonium compounds.

The reaction of 242PuO2 with HF and LiF under hydrothermal conditions results in the formation of Li4PuF8 and LiPuF5. These compounds were structurally characterized using single-crystal X-ray diffraction, and UV-vis-near-IR absorption spectroscopy was employed to confirm the oxidation state of the plutonium in the compounds as 4+. The structure of Li4PuF8 consists of [PuF8]4- anions that adopt a bicapped trigonal-prismatic geometry with approximate C2v symmetry. These molecules are bridged by Li+ cations. In contrast, LiPuF5 forms a dense three-dimensional network constructed from [PuF9]5- units that are bridged by F- anions. The Pu4+ cations are found within tricapped trigonal prisms. Extensive theoretical analysis of the electronic and bonding interactions is included with a comparison between the results derived from complete-active-space self-consistent-field at different levels of theory, quantum theory of atoms in molecules, interacting quantum atom, natural localized molecular orbital, and Wiberg bond order analyses. Covalent interactions in these compounds are examined, and intramolecular trends in covalent and electrostatic interactions are discussed.

This brief introduction to the synthesis and chemistry of elements discovered since 1940 is focused primarily on Z=93–118. The goal of this work is not to simply catalogue the nuclear fusion reactions needed to prepare new elements, but rather to focus on the chemical and physical properties that these elements possess. These elements share a single common feature in that they all have large Z values, and thus have electronic structures that are significantly altered by both scalar relativistic effects and spin-orbit coupling. These effects scale nonlinearly with increasing Z and create unexpected deviations both across series and down groups of elements. The magnitude of these effects is large enough that orbital energies rearrange and mix in ways that complicate incomplete depictions of electronic structure that are based solely on electron repulsion. Thus, the primary aim of this review is to document the impact of relativistic effects on electronic structure and how this has altered not just our understanding of the chemistry of heavy elements, but has even created in the need to rearrange the Periodic Table itself.

The total kinetic energy (TKE) release in the fast neutron-induced fission of various actinide nuclei was measured for neutron energies for En=2.6-100 MeV at the Weapons Neutron Research facility of the Los Alamos National Laboratory. The data are compared to the GEF model of the fission process. The variances of the TKE distributions appear to decrease with increasing Z and A of the fissioning systems.

High entropy alloys (HEA) are an unusual class of materials where mixtures of elements are stochastically arrayed on a simple crystalline lattice. These systems exhibit remarkable functionality, often along several distinct axes: e.g., the examples [TaNb]1-x(TiZrHf)x are high strength and damage resistant refractory metals that also exhibit superconductivity with large upper critical fields. Here we report the discovery of an f-electron containing HEA, [TaNb]0.31(TiUHf)0.69, which is the first to include an actinide ion. Similar to the Zr-analogue, this material crystallizes in a body-centered cubic lattice with the lattice constant a = 3.41(1) Å and exhibits phonon mediated superconductivity with a transition temperatures Tc ≈ 3.2 K and upper critical fields Hc2 ≈ 6.4 T. These results expand this class of materials to include actinide elements, shows that superconductivity is robust in this sub-group, and opens the path towards leveraging HEAs as functional waste forms for a variety of radioisotopes.

The simple system of tetraammonium octafluorouranate is employed to derive a fundamental understanding of the uranium–fluorine interaction. The structure is composed of isolated molecules, enabling a detailed examination of the U4+ (f2) ion. Characterization of single-crystals by X-ray diffraction, absorption spectroscopy, and magnetic analysis up to 45 T is combined with extensive theoretical treatment by CASSCF. The influence of different active spaces and representations of the structure is examined in the context of the experimental evidence. The Interacting Quantum Atoms method (IQA) is used to examine the nature of the U–F bond, concluding that there is a non-negligible degree of covalent character (9% of the total bond energy) in [UF8]4−. For the structural and theoretical reasons discussed herein, it is proposed that the structure of (NH4)4UF8 may be appropriately employed as a benchmark compound for future theoretical characterization of U(IV).

An unexpected product was obtained from slow evaporation in acidic media, as a protonated nitro­gen is combined with a di­sulfide bond between a pair of 2-mercaptonicotinic acid moieties., The title compound {systematic name: 3-carb­oxy-2-[2-(3-carb­oxy­pyridin-2-yl)disulfan-1-yl)]pyridin-1-ium chloride monohydrate}, C12H9N2O4S2 +·Cl−·H2O, crystallizes in the triclinic space group P . A pair of 2-mercaptonicotinic acid moieties is connected by a 2,2′-di­sulfide bond with a dihedral angle of 78.79 (3)°. One of the N atom is protonated, as are both carboxyl­ate groups, resulting in an overall +1 charge on the dimer. The structure comprises a zigzagging layer of the dimerized di­thio­dinicotinic acid rings, with charge-balancing chloride ions and water mol­ecules between the layers. Hydrogen bonding between the chloride and water sites with the dimer appears to hold the structure together. Nearest neighbor nicotinic acid rings are offset when viewed down the a axis, suggesting no added stability from ring stacking. The asymmetric unit corresponds to the empirical formula of the compound, and it packs with two formula units per unit cell.

The structure of tetra­lithium octa­fluorido­zirconate has been redetermined by high-resolution single-crystal X-ray diffraction. This result is largely consistent with a prior report, but with significant improvements in precision., Presented herein is the crystal-structure redetermination of Li4ZrF8 from single-crystal X-ray data. Alkali zirconium fluorides are important in nuclear-relevant technologies, and zirconium is commonly employed as an analogue for tetra­valent f-block elements. The previous structure report of this species is based on powder X-ray data [Dugat et al. (1995 ▸). J. Solid State Chem. 120, 187–196] but there has never been a refined structure model from single-crystal data. The octa­fluorido­zirconate moieties are held together by electrostatic attraction to lithium ions without sharing of fluoride sites between zirconium(IV) ions.

Two new sodium uranium(IV) pentafluorides were synthesized from uranium dioxide, HF, and NaF using mild hydrothermal conditions. β-NaUF5·H2O has greater lattice energy than previously-known α-NaUF5·H2O and possesses lower symmetry with the latter compound being orthorhombic, whereas β-NaUF5·H2O is monoclinic. Trigonal β-NaUF5 also possesses different connectivity between the [UFn] building units than the α-phase, with higher symmetry and greater lattice energy than orthorhombic α-NaUF5. The single crystal absorption spectra of these compounds are also reported and compared.

The reaction of

Curium is unique in the actinide series because its half-filled 5f

The simple system of tetraammonium octafluorouranate is employed to derive a fundamental understanding of the uranium-fluorine interaction. The structure is composed of isolated molecules, enabling a detailed examination of the U

Two new sodium uranium(iv) pentafluorides were synthesized from uranium dioxide, HF, and NaF using mild hydrothermal conditions. β-NaUF

bibtex: ISI:000412043000020 bibtex\location:'1155 16TH ST, NW, WASHINGTON, DC 20036 USA',publisher:'AMER CHEMICAL SOC',type:'Article',affiliation:'Albrecht-Schmitt, TE (Reprint Author), Florida State Univ, Dept Chem & Biochem, Tallahassee, FL 32306 USA. Silver, Mark A.; Cary, Samantha K.; Arico, Alexandra A.; Galmin, Gregory A.; Wang, Jamie C.; Clark, Ronald J.; Chemey, Alexander; Eaton, Teresa M.; Marsh, Matthew L.; Seidler, Kevin; Galley, Shane S.; van de Burgt, Lambertus; Hobart, David E.; Hanson, Kenneth; Albrecht-Schmitt, Thomas E., Florida State Univ, Dept Chem & Biochem, Tallahassee, FL 32306 USA. Garza, Alejandro J.; Scuseria, Gustavo E., Rice Univ, Dept Chem, POB 1892, Houston, TX 77251 USA. Baumbach, Ryan E.; Chen, Kuan-Wen, Natl High Magnet Field Lab, Tallahassee, FL 32310 USA. Johnson, Jason A.; Gray, Ashley L., Florida State Univ, Environm Hlth & Safety, Tallahassee, FL 32306 USA. Van Cleve, Shelley M., Oak Ridge Natl Lab, Nucl Mat Proc Grp, One Bethel Valley Rd, Oak Ridge, TN 37830 USA. Gendron, Frederic; Autschbach, Jochen, Univ Buffalo State Univ New York, Dept Chem, Buffalo, NY 14260 USA. Maron, Laurent, Inst Natl Sci Appl, Lab Phys & Chim Nanoobjets, F-31077 Toulouse 4, France. Speldrich, Manfred; Koegerler, Paul, Rhein Westfal TH Aachen, Inst Anorgan Chem, D-52074 Aachen, Germany. Celis-Barros, Cristian; Paez-Hernandez, Dayan; Arratia-Perez, Ramiro, Univ Andres Bello, Fac Ciencias Exactas, Ctr Nanociencias Aplicadas, Republ 275, Santiago, Chile. Ruf, Michael, Bruker AXS, 5465 East Cheryl Pkwy, Madison, WI 53711 USA.','author-email':'albrecht-schinitt@chem.fsu.edu',da:'2018-12-05','doc-delivery-number':'FI5SB','funding-acknowledgement':'U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Elements Chemistry Program [DE-FG02-13ER16414, DE-SC0001136, DE-FG02-04ER15523]; Welch Foundation Chair [C-0036]; National Science Foundation [DMR-1157490, DGE-1449440]; State of Florida; U.S. Department of Energy; CBFO Fellowship Program (MAS) - U.S. Department of Energy','funding-text':'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 \textlessSUP\textgreater249\textless/SUP\textgreaterBk 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.','journal-iso':'J. Am. Chem. Soc.','keywords-plus':'VALENCE BASIS-SETS; ENERGY-ADJUSTED PSEUDOPOTENTIALS; MOLECULAR-ORBITAL METHODS; CRYSTAL-STRUCTURE; AB-INITIO; MAGNETIC-SUSCEPTIBILITY; COORDINATION GEOMETRY; PERTURBATION-THEORY; IONIC-RADII; PLUTONIUM','number-of-cited-references':'113',oa:'Bronze','orcid-numbers':'Kogerler, Paul/0000-0001-7831-3953 Gendron, Frederic/0000-0002-1896-3978 Hanson, Kenneth/0000-0001-7219-7808 Albrecht-Schmitt, Thomas/0000-0002-2989-3311 Chemey, Alexander/0000-0002-0679-7845 Paez, Dayan/0000-0003-2747-9982 Speldrich, Manfred/0000-0002-8626-6410 Celis-Barros, Cristian/0000-0002-4685-5229 Garza, Alejandro/0000-0001-6995-2833','research-areas':'Chemistry','researcherid-numbers':'Kogerler, Paul/H-5866-2013','times-cited':'5','unique-id':'ISI:000412043000020','usage-count-last-180-days':'8','usage-count-since-2013':'36','web-of-science-categories':'Chemistry, Multidisciplinary'\; International audience; The reaction of Bk-249(OH)(4) with iodate under hydro thermal 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(Io(3))(3) consists of nine-coordinate BO cations that are bridged by iodate anions to yield layers that are isomorphous with those found for Am-III, Cf-III, 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 Zr-IV cation. Bk-III-O and Bk-IV-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 Bkill in these crystals. In addition to luminescence from Bkul 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 Bk-249 (t(1/2) = 320 d) causes oxidation of Bk-III and only Bk-IV is present after a few days with concomitant loss of both the Bk-III 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 Bk-IV that does not strictly adhere to Russel Saunders coupling and Hund's Rule even though it possesses a half-filled Sf(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 Bk-IV-O bonds that distributes the 5f electrons onto the ligands. These factors are absent or diminished in other f(7) ions such as Gd-III or Cm-III.

A Digital Data Acquisition System (DDAS) composed of 16-channel FPGA-programmable modules running 12-bit 100 Mega-Samples Per Second (MSPS) ADCs has been implemented on three different experimental arrays at the National Superconducting Cyclotron Laboratory (NSCL) encompassing charged particle spectroscopy, high and low energy-resolution photon detection, and neutron time-of-flight measurements. DDAS has increased the experimental capabilities of each array by providing energy and time measurements with nearly zero dead-time, low energy thresholds, and large dynamic range. The performance of the DDAS Analog-to-Digital Converters (ADC)s was characterized, and energy and time resolutions were compared with traditional analog systems. We have demonstrated a 14- to 15-bit peak-sensing equivalent resolution when applied to semiconductor detectors and 500 ps time resolution for LaBr3 detectors measuring coincident radiation with signal amplitudes of ≈13% of the input range of the ADC. Details regarding the operation of the system at NSCL including digital filtering, triggering, clock distribution, and event-building are discussed along with applications to selected detector systems.

We report on synthesis and characterization of the compounds A 6W4Al43 (A = U and Pu), that form in the hexagonal Ho6Mo4Al43 caged-structure family. The A ions reside within W/Al cages where the A-A nearest neighbors form dimers between adjacent W/Al cages, with U-U and Pu-Pu distances of 3.3892 [Formula: see text] and 3.4080 [Formula: see text], respectively. While the W/Al networks provide environments similar to those of other cage-like materials (e.g. filled skutterudites), the atomic displacement parameters from single crystal x-ray diffraction measurements show that the A-ions do not exhibit rattling behavior. We find that there is site interchange disorder on one of the W/Al sites. Magnetic susceptibility measurements show that U6W4Al43 displays anisotropic Curie-Weiss behavior where it fits to the data yield an effective magnetic moment near 2.0 [Formula: see text]/U. At low temperatures the magnetic susceptibility deviates from the Curie-Weiss temperature dependence and eventually saturates to a constant value. In contrast, Pu6W4Al43 displays nearly temperature independent Pauli paramagnetism for all temperatures, as would be expected if the 5f -electrons are delocalized. The electrical resistivity for U6W4Al43 increases slightly with the decreasing temperature, suggesting that it is dominated by f -electronic hybridization effects and disorder scattering that originates from the W/Al site interchange. Specific heat measurements for U6W4Al43 further reveal an enhanced electronic Sommerfeld coefficient that is consistent with a moderately enhanced charge carrier effective mass. Together these measurements expose these materials as hosts for unstable f -electron magnetism, where the novel cage-like structures control the phenomena through the spacing between the A ions. Through this combination of mild magnetism, the low cost elements of the Al-W cages, and chemical tunability that has been shown for related materials in the same structure, the A 6W4Al43 compounds emerge as promising nuclear waste-forms for transuranics, while the wider family of materials makes an appealing environment for studying f -electron physics in a novel structure.

Beta-decay spectroscopy experiments are limited by the detection efficiency of ions and electrons in the experimental setup. While there is a variety of different experimental setups in use for beta-decay spectroscopy, one popular choice is silicon double-sided strip detectors (DSSD). The higher Z of Ge and greater availability of thicker detectors as compared to Si potentially offer dramatic increases in the detection efficiency for beta-decay electrons. In this work, a planar GeDSSD has been commissioned for use in beta-decay spectroscopy experiments at the National Superconducting Cyclotron Laboratory (NSCL). The implantation response of the detector and its beta-decay detection efficiency is discussed.

The internal-conversion and internal-pair-production decays of the first excited 0+ state in Ni68 are studied following the β decay of Co68. A novel experimental technique, in which the ions of Co68 were implanted into a planar germanium double-sided strip detector and which required digital pulse processing, is developed. The values for the energy of the first excited 0+ state and the electric monopole transition strength from the first excited 0+ state to the ground state in Ni68 are determined to be 1605(3) keV and 7.6(4)×10-3, respectively. Comparisons of the experimental results to Monte Carlo shell-model calculations suggest the coexistence between a spherical ground state and an oblate first excited 0+ state in Ni68. © 2014 American Physical Society. ispartof: Physical Review C, Nuclear Physics vol:89 issue:2 status: published