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A new binary compound, NpSe2, possesses metal-chalcogen and chalcogen-chalcogen interactions different from those reported for other metal dichalcogenides. Its structure is incommensurately modulated and features linear Se chains and valence-ambiguous Np cations.

The chemistry of trivalent transplutonium ions (Am3+ , Cm3+ , Bk3+ , Cf3+ , Es3+ …) is usually perceived as monotonic and paralleling that of the trivalent lanthanide series. Herein, we present the first extended X-ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to much shorter metal-oxygen nearest-neighbor bond lengths in the case of Cf3+ . Corroborating those results, density functional theory calculations, extended to Es3+ , suggest that the shorter Cf-O and Es-O bonds could arise from the departure of the coordinated water molecule and contraction of the ligand around the metal relative to the other [MIII DTPA(H2 O)]2- (M=Am, Cm, Bk) complexes. Taken together, these experimental and theoretical results demonstrate inhomogeneity within the trivalent transplutonium series that has been insinuated and debated in recent years, and that may also be leveraged for future nuclear waste reprocessing technologies.

The black title compounds are synthesized by reactions of the elements in Sb2Q3 (Q: S, Se) fluxes at 900 °C for 7 d and characterized by single crystal XRD, UV/VIS/NIR diffuse reflectance spectroscopy, and magnetic susceptibility measurements.

Dark red single crystals of PrLnYb{sub 2}S{sub 6} (Ln=Pr/Yb, Tb, Dy) have been synthesized through the reactions of elemental rare earth metals and S using a Sb{sub 2}S{sub 3} flux at 1000 deg. C. These isotypic compounds adopt the F-Ln{sub 2}S{sub 3} three-dimensional open-channel structure type. Eight-coordinate Pr{sup 3+} ions sit in the channels that are constructed from three different edge-shared double chains running down the b-axis that contain Yb(1)S{sub 6} octahedra, Yb(2)S{sub 6} octahedra, and LnS{sub 7} monocapped trigonal prisms. Each double chain connects to four other neighbors by sharing vertices and edges. Considerable disordering in Ln positions was observed in single X-ray diffraction experiments only in the case of Pr/Yb. Least-squares refinements gave rise to the formulas of Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, of PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6}, which are confirmed by the elemental analysis and magnetic susceptibility measurements. Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6} are paramagnetic down to 2 K, without any indications of long-range magnetic ordering. The optical transitions for Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6} are at approximately 1.6 eV. Crystallographic data are listed as an example for PrTbYb{sub 2}S{sub 6}: monoclinic, spacemore » group P2{sub 1}/m, a=10.9496(10) A, b=3.9429(4) A, c=11.2206(10) A, {beta}=108.525(2){sup o}, V=459.33(7) A{sup 3}, Z=2. - Graphical abstract: An illustration of the three-dimensional structure of PrTbYb{sub 2}S{sub 6} viewed along the b-axis.« less

δ-Ln2−xLuxS3 (Ln=Ce, Pr, Nd; x=0.67–0.71) compounds have been synthesized through the reaction of elemental rare-earth metals and S using a Sb2S3 flux at 1000 °C. These compounds are isotypic with CeTmS3, which has a complex three-dimensional structure. It includes four larger Ln3+ sites in eight- and nine-coordinate environments, two disordered seven-coordinate Ln3+/Lu3+ positions, and two six-coordinate Lu3+ ions. The structure is constructed from one-dimensional chains of LnSn (n=6–9) polyhedra that extend along the b-axis. These polyhedra share faces or edges with two neighbors within the chains, while in the [ac] plane they share edges and corners with other chains. Least square refinements gave rise to the formulas of δ-Ce1.30Lu0.70S3, δ-Pr1.29Lu0.71S3 and δ-Nd1.33Lu0.67S3, which are consistent with the EDX analysis and magnetic susceptibility data. δ-Ln2−xLuxS3 (Ln=Ce, Pr, Nd; x=0.67–0.71) show no evidence of magnetic ordering down to 5 K. Optical properties measurements show that the band gaps for δ-Ce1.30Lu0.70S3, δ-Pr1.29Lu0.71S3, and δ-Nd1.33Lu0.67S3 are 1.25, 1.38, and 1.50 eV, respectively. Crystallographic data: δ-Ce1.30Lu0.70S3, monoclinic, space group P21/m, a=11.0186(7), b=3.9796(3), c=21.6562(15) A, β=101.6860(10), V=929.93(11), Z=8; δ-Pr1.29Lu0.71S3, monoclinic, space group P21/m, a=10.9623(10), b=3.9497(4), c=21.5165(19) A, β=101.579(2), V=912.66(15), Z=8; δ-Nd1.33Lu0.67S3, monoclinic, space group P21/m, a=10.9553(7), b=3.9419(3), c=21.4920(15) A, β=101.5080(10), V=909.47(11), Z=8.

Syntheses, Structure, Magnetism, and Optical Properties of Lutetium- based Interlanthanide Selenides Geng Bang Jin, † Eun Sang Choi, ‡ Robert P. Guertin, § James S. Brooks, ‡ Corwin H. Booth, £ and Thomas E. Albrecht-Schmitt †,* Department of Chemistry and Biochemistry and the E. C. Leach Nuclear Science Center, Auburn University, Auburn, Alabama 36849 Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720 Published in Inorg. Chem. 46, 9213 (2007). Abstract

New high-performance ferroelectric materials based on Pb(Zr{sub 1-x}Ti{sub x})O{sub 3} (PZT) that are doped with cryolite-type strontium niobate (SNO, Sr{sub 4}(Sr{sub 2-2y/3}Nb{sub 2+2y/3})O{sub 11+y}V{sub 0,1-y} with 0 {le} y {le} 1), hence denoted PZT:SNO, and their microscopic structure are described. The combination of exceptional piezoelectric properties, i.e. a piezoelectric strain constant of d{sub 33} {approx} 760 pm/V, with excellent stability and degradation resistance makes ferroelectric PZT:SNO solid solutions very attractive for use in novel and innovative piezoelectric actuator and transducer applications. Extended X-ray absorption fine-structure (EXAFS) analyses of PZT:SNO samples revealed that {approx}10 % of the Sr cations occupy the nominal B-sites of the perovskite-type PZT host lattice. This result was supported by EXAFS analyses of both a canonical SrTiO{sub 3} perovskite and two SNO model and reference compounds. Fit models that do not account for Sr cations on B-sites were ruled out. A clear Sr-Pb peak in Fourier transformed EXAFS data visually confirmed this structural model. The generation of temporary oxygen vacancies and the intricate defect chemistry induced by SNO-doping of PZT are crucial for the exceptional materials properties exhibited by PZT:SNO materials.