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Sample records for gd crystal structure

  1. Crystal structure and electronic states of Co and Gd ions in a Gd0.4Sr0.6CoO2.85 single crystal

    Science.gov (United States)

    Platunov, M. S.; Dudnikov, V. A.; Orlov, Yu. S.; Kazak, N. V.; Solovyov, L. A.; Zubavichus, Ya. V.; Veligzhanin, A. A.; Dorovatovskii, P. V.; Vereshchagin, S. N.; Shaykhutdinov, K. A.; Ovchinnikov, S. G.

    2016-02-01

    X-ray diffraction and X-ray absorption near edge structure (XANES) spectra have been measured at the Co K-edge and Gd L 3-edge in GdCoO3 and Gd0.4Sr0.6CoO2.85 cobaltites. The effect of Sr substitution on the crystal structure and electronic and magnetic states of Co3+ ions in a Gd0.4Sr0.6CoO2.85 single crystal has been analyzed. The XANES measurements at the Co K-edge have not showed a noticeable shift of the absorption edge with an increase in the concentration of Sr. This indicates that the effective valence of cobalt does not change. An increase in the intensity of absorption at the Gd L 3-edge is due to an increase in the degree of hybridization of the Gd(5 d) and O(2 p) states. The effect of hole doping on the magnetic properties results in the appearance of the ferromagnetic component and in a significant increase in the magnetic moment.

  2. Stabilization of crystal and magnetic structure of Gd2Al1-xInx

    International Nuclear Information System (INIS)

    Niazi, M.; Yazdani, A.

    2006-01-01

    A random mixture of two compounds with different type of crystal structure and magnetic characteristic which can lead to a new phase, is studied to find out the critical point at which both of them stabilized. such an interesting random system can be found by; 1) Gd 2 Al with two different magnetic phase transition on which T c is unstable 2) Gd 2 In which is also shows two magnetic phase transition, but completely different with Gd 2 Al on which T N is unstable. The stabilized point which is consider experimentally by X-Ray diffraction and theoretically by WIEN2K is suggested to be at x=0.3 where it is a good agreement between these two methods.

  3. The new carbodiimide Li_2Gd_2Sr(CN_2)_5 having a crystal structure related to that of Gd_2(CN_2)_3

    International Nuclear Information System (INIS)

    Unverfehrt, Leonid; Stroebele, Markus; Meyer, H. Juergen

    2013-01-01

    The new carbodiimide compounds Li_2RE_2Sr(CN_2)_5 (RE = Sm, Gd, Eu, Tb) were prepared by a straight forward solid state metathesis reaction of REF_3, SrF_2, and Li_2(CN_2) at around 600 C. The crystal structure of Li_2Gd_2Sr(CN_2)_5 was solved based on X-ray single-crystal diffraction data. Corresponding Li_2RE_2Sr(CN_2)_5 compounds were analyzed by isotypic indexing of their powder patterns. The crystal structure of Li_2Gd_2Sr(CN_2)_5 can be well related to that of Gd_2(CN_2)_3, because both structures are based on layered structures composed of close packed layers of [N=C=N]"2"- sticks, alternating with layers of metal ions. The crystal structure of Li_2Gd_2Sr(CN_2)_5 can be considered to contain an ABC layer sequence of [N = C=N]"2"- layers with the interlayer voids being occupied by (three) distinct types of cations. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Crystal structure and electrical resistivity studies of Gd(Fe1-x Cox)2 intermetallics

    International Nuclear Information System (INIS)

    Onak, M.; Guzdek, P.; Stoch, P.; Chmist, J.; Bednarski, M.; Panta, A.; Pszczola, J.

    2007-01-01

    From X-ray analysis (295 K) it was found that the cubic, MgCu 2 -type, Fd3m crystal structure appears across the Gd(Fe 1-x Co x ) 2 series. Electrical resistivity measurements for the Gd(Fe 1-x Co x ) 2 intermetallics were performed in a wide temperature region and the parameters characterizing the resistivity dependence on temperature and composition were determined. The differential of the electrical resistivity against temperature was used to estimate Curie temperatures. The Curie temperature versus x, high and moderately increasing in the iron-rich area, rapidly drops in the cobalt-rich region. The obtained results are compared with the data known for the Dy(Fe 1-x Co x ) 2 series. The Curie temperature is related to both the number of 3d electrons and the de Gennes factor

  5. Crystal, magnetic, calorimetric and electronic structure investigation of GdScGe1-x Sb x compounds

    Science.gov (United States)

    Guillou, F.; Pathak, A. K.; Hackett, T. A.; Paudyal, D.; Mudryk, Y.; Pecharsky, V. K.

    2017-12-01

    Experimental investigations of crystal structure, magnetism and heat capacity of compounds in the pseudoternary GdScGe-GdScSb system combined with density functional theory projections have been employed to clarify the interplay between the crystal structure and magnetism in this series of RTX materials (R  =  rare-earth, T   =  transition metal and X  =  p-block element). We demonstrate that the CeScSi-type structure adopted by GdScGe and CeFeSi-type structure adopted by GdScSb coexist over a limited range of compositions 0.65 ≤slant x ≤slant 0.9 . Antimony for Ge substitutions in GdScGe result in an anisotropic expansion of the unit cell of the parent that is most pronounced along the c axis. We believe that such expansion acts as the driving force for the instability of the double layer CeScSi-type structure of the parent germanide. Extensive, yet limited Sb substitutions 0 ≤slant x disappearance of the induced magnetic moments on Sc. For the parent antimonide, heat capacity measurements indicate an additional transition below the main antiferromagnetic transition.

  6. Pressure effects on crystal structures and magnetic properties of RCo{sub 5} (R = Y or Gd) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Burzo, E. [Faculty of Physics, Babes-Bolyai University Cluj-Napoca 400084 (Romania); Vlaic, P. [Faculty of Physics, Babes-Bolyai University Cluj-Napoca 400084 Romania and University of Medicine and Pharmacy Iuliu Hatieganu, Physics and Biophysics Department Cluj-Napoca (Romania)

    2013-11-13

    The pressure dependences of crystal structures and magnetic properties of YCo{sub 5} and GdCo{sub 5} compounds are analysed based on band structure calculations. Isomorphic transitions were evidenced for relative volumes v/v{sub 0} = 0.91 and 0.86, for YCo{sub 5} and GdCo{sub 5}, respectively. At the transition, there is a higher decrease of cobalt moments at 3g sites as compared to those located in 2c ones. The induced polarizations on Y4d and Gd5d bands, by short range interactions, are linearly dependent on the magnetizations of cobalt atoms situated in their neighborhood. The isomorphic transitions are analysed in correlations with band structures.

  7. Hydrothermal synthesis, crystal structure, luminescent and magnetic properties of a new mononuclear GdIII coordination complex

    Science.gov (United States)

    Coban, Mustafa Burak

    2018-06-01

    A new GdIII coordination complex, {[Gd(2-stp)2(H2O)6].2(4,4'-bipy).4(H2O)}, complex 1, (2-stp = 2-sulfoterephthalate anion and 4,4'-bipy = 4,4'-bipyridine), has been synthesized by hydrothermal method and characterized by elemental analysis, solid state UV-Vis and FT-IR spectroscopy, single-crystal X-ray diffraction, solid state photoluminescence and variable-temperature magnetic measurements. The crystal structure determination shows that GdIII ions are eight coordinated and adopt a distorted square-antiprismatic geometry. Molecules interacting through intra- and intermolecular (O-H⋯O, O-H⋯N) hydrogen bonds in complex 1, give rise to 3D hydrogen bonded structure and the discrete lattice 4,4'-bipy molecules occupy the channel of the 3D structure. π-π stacking interactions also exist 4,4'-bipy-4,4'-bipy and 4,4'-bipy-2-stp molecule rings in 3D structures. Additionally, solid state photoluminescence properties of complex 1 at room temperature have been investigated. Under the excitation of UV light (at 349 nm), the complex 1 exhibited green emissions (at 505 nm) of GdIII ion in the visible region. Furthermore, Variable-temperature magnetic susceptibility and isothermal magnetization as function of external magnetic field studies reveal that complex 1 displays possible antiferromagnetic interaction.

  8. Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

    Science.gov (United States)

    Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

    2018-05-01

    In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

  9. Thermoelectric properties, crystal and electronic structure of semiconducting RECuSe{sub 2} (RE = Pr, Sm, Gd, Dy and Er)

    Energy Technology Data Exchange (ETDEWEB)

    Esmaeili, Mehdi [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada); Tseng, Yu-Chih [CANMET Materials, Natural Resources Canada, 183 Longwood Road South, Hamilton, Ontario L8P 0A5 (Canada); Mozharivskyj, Yurij, E-mail: mozhar@mcmaster.ca [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada)

    2014-10-15

    Highlights: • Crystal and electronic structure of monoclinic and trigonal RECuSe{sub 2} phases. • Thermoelectric properties of the RECuSe{sub 2} phases. • Temperature stability of the RECuSe{sub 2} phases. - Abstract: The ternary RECuSe{sub 2} phases have been prepared and structurally characterized. They adopt either a monoclinic structure (P2{sub 1}/c, z = 4) for lighter rare earths (RE = Pr, Sm and Gd) or Cu-disordered trigonal structure for heavier rare-earths (P3{sup ¯}m1, z = 1, RE = Dy and Er). The resistivity and Seebeck coefficient measurements on GdCuSe{sub 2}, DyCuSe{sub 2} and ErCuSe{sub 2} indicate that the studied phases are p-type semiconductors with relatively small activation energies (0.045–0.11 eV). However, their electrical resistivities are too high (0.45–220 Ω cm at room temperature) to make them competitive thermoelectric materials. Electronic structure calculations indicate presence of a band gap in the RECuSe{sub 2} phases.

  10. Thermoelectric properties, crystal and electronic structure of semiconducting RECuSe2 (RE = Pr, Sm, Gd, Dy and Er)

    International Nuclear Information System (INIS)

    Esmaeili, Mehdi; Tseng, Yu-Chih; Mozharivskyj, Yurij

    2014-01-01

    Highlights: • Crystal and electronic structure of monoclinic and trigonal RECuSe 2 phases. • Thermoelectric properties of the RECuSe 2 phases. • Temperature stability of the RECuSe 2 phases. - Abstract: The ternary RECuSe 2 phases have been prepared and structurally characterized. They adopt either a monoclinic structure (P2 1 /c, z = 4) for lighter rare earths (RE = Pr, Sm and Gd) or Cu-disordered trigonal structure for heavier rare-earths (P3 ¯ m1, z = 1, RE = Dy and Er). The resistivity and Seebeck coefficient measurements on GdCuSe 2 , DyCuSe 2 and ErCuSe 2 indicate that the studied phases are p-type semiconductors with relatively small activation energies (0.045–0.11 eV). However, their electrical resistivities are too high (0.45–220 Ω cm at room temperature) to make them competitive thermoelectric materials. Electronic structure calculations indicate presence of a band gap in the RECuSe 2 phases

  11. Synthesis, crystal structure, and physical properties of the Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8} phases

    Energy Technology Data Exchange (ETDEWEB)

    Forbes, Scott; Yuan, Fang [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Kosuda, Kosuke; Kolodiazhnyi, Taras [Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Mozharivskyj, Yurij, E-mail: mozhar@mcmaster.ca [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada)

    2016-01-15

    The second and third known rare-earth bismuthide oxides, Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8}, have been discovered via high temperature reactions at 1300 °C. Like its Gd–Sb–O counterparts, the Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8} phases crystallize in the monoclinic C2/m space group, with the latter containing disordered Bi atoms along the b direction of the unit cell. Unlike the RE{sub 8}Sb{sub 3}O{sub 8} series, the formation of the Gd{sub 3}BiO{sub 3} phase does not necessarily precede the formation of Gd{sub 8}Bi{sub 3}O{sub 8}, which is likely due to the difficulty of accommodating bismuth in the RE–O framework due to its larger size. Physical property measurements performed on a pure Gd{sub 8}Bi{sub 3}O{sub 8} sample reveal semiconducting behavior. Although electronic structure calculations predict metallic behavior due to an unbalanced electron count, the semiconducting behavior originates from the Anderson localization of the Bi p states near the Fermi level as a result of atomic disorder. - Graphical abstract: Reaction of GdBi and Gd{sub 2}O{sub 3} at high temperatures yields Gd–Bi–O phases. - Highlights: • Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8}, the second and third rare-earth bismuthide oxides, have been discovered. • Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8} are isostructural with RE{sub 3}SbO{sub 3} and RE{sub 8}Sb{sub 3}O{sub 8}. • Gd{sub 8}Bi{sub 3}O{sub 8} displays semiconducting behavior despite an unbalanced electron count. • Anderson localization of Bi p states results in semiconducting behavior in Gd{sub 8}Bi{sub 3}O{sub 8}.

  12. Self-powdering and nonlinear optical domain structures in ferroelastic β'-Gd2(MoO4)3 crystals formed in glass

    International Nuclear Information System (INIS)

    Tsukada, Y.; Honma, T.; Komatsu, T.

    2009-01-01

    Ferroelastic β'-Gd 2 (MoO 4 ) 3 , (GMO), crystals are formed through the crystallization of 21.25Gd 2 O 3 -63.75MoO 3 -15B 2 O 3 glass (mol%), and two scientific curious phenomena are observed. (1) GMO crystals formed in the crystallization break into small pieces with a triangular prism or pyramid shape having a length of 50-500 μm spontaneously during the crystallizations in the inside of an electric furnace, not during the cooling in air after the crystallization. This phenomenon is called 'self-powdering phenomenon during crystallization' in this paper. (2) Each self-powdered GMO crystal grain shows a periodic domain structure with different refractive indices, and a spatially periodic second harmonic generation (SHG) depending on the domain structure is observed. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of second harmonic intensities that GMO crystals are oriented in each crystal grain and the orientation of (MoO 4 ) 2- tetrahedra in GMO crystals changes periodically due to spontaneous strains in ferroelastic GMO crystals. - Graphical abstract: This figure shows the polarized optical photograph at room temperature for a particle (piece) obtained by a heat treatment of the glass at 590 deg. C for 2 h in an electric furnace in air. This particle was obtained through the self-powdering behavior in the crystallization of glass. The periodic domain structure is observed. Ferroelastic β'-Gd 2 (MoO 4 ) 3 crystals are formed in the particle, and second harmonic generations are detected, depending on the domain structure.

  13. A sodium gadolinium phosphate with two different types of tunnel structure: Synthesis, crystal structure, and optical properties of Na3GdP2O8

    International Nuclear Information System (INIS)

    Fang, M.; Cheng, W.-D.; Zhang, H.; Zhao, D.; Zhang, W.-L.; Yang, S.-L.

    2008-01-01

    A sodium gadolinium phosphate crystal, Na 3 GdP 2 O 8 , has been synthesized by a high-temperature solution reaction, and it exhibits a new structural family of the alkali-metal-rare-earth phosphate system. Although many compounds with formula M 3 LnP 2 O 8 have been reported, but they were shown to be orthorhombic [R. Salmon, C. Parent, M. Vlasse, G. LeFlem, Mater. Res. Bull. 13 (1978) 439] rather than monoclinic as shown in this paper. Single-crystal X-ray diffraction analysis shows the structure to be monoclinic with space group C2/c and the cell parameters: a=27.55 (25), b=5.312 (4), c=13.935(11) A, β=91.30(1) o , and V=2038.80 A 3 , Z=4. Its structure features a three-dimensional GdP 2 O 8 3- anionic framework with two different types of interesting tunnels at where Na atoms are located by different manners. The framework is constructed by Gd polyhedra and isolated PO 4 tetrahedra. It is different from the structure of K 3 NdP 2 O 8 [R. Salmon, C. Parent, M. Vlasse, G. LeFlem, Mater. Res. Bull. 13 (1978) 439] with space group P2 1 /m that shows only one type of tunnel. The emission spectrum and the absorption spectrum of the compound have been investigated. Additionally, the calculations of band structure, density of states, dielectric constants, and refractive indexes have been also performed with the density functional theory method. The obtained results tend to support the experimental data. - Graphical abstract: Projection of the structure of Na 3 GdP 2 O 8 with a unit cell edge along the b-axis. The Na-O bonds are omitted for clarity

  14. Peculiarities of component interaction in {Gd, Er}-V-Sn Ternary systems at 870 K and crystal structure of RV6Sn6 stannides

    International Nuclear Information System (INIS)

    Romaka, L.; Stadnyk, Yu.; Romaka, V.V.; Demchenko, P.; Stadnyshyn, M.; Konyk, M.

    2011-01-01

    Highlights: → {Gd, Er}-V-Sn ternary systems at 870 K are characterized by formation of stannides with general compositions RV 6 Sn 6 . → Isostructural RV 6 Sn 6 compounds were also found with Y, Dy, Ho, Tm, and Lu. → The crystal structure of RV 6 Sn 6 compounds was determined by powder diffraction method. → Structural analysis showed that RV 6 Sn 6 compounds (R = Gd, Dy-Tm, Lu) are disordered; YV 6 Sn 6 is characterized by structure ordering. - Abstract: The phase equilibria in the Gd-V-Sn and Er-V-Sn ternary systems were studied at 870 K by means of X-ray and metallographic analyses in the whole concentration range. Both Gd-V-Sn and Er-V-Sn systems are characterized by formation of one ternary compound at investigated temperature, with stoichiometry RV 6 Sn 6 (SmMn 6 Sn 6 -type, space group P6/mmm, a = 0.55322(3) nm, c = 0.91949(7) nm for Gd, a = 0.55191(2) nm, c = 0.91869(8) nm for Er). Solubility of the third component in the binary compounds was not observed. Compounds with the SmMn 6 Sn 6 -type were also found with Dy, Ho, Tm, and Lu, while YV 6 Sn 6 compound crystallizes in HfFe 6 Ge 6 structure type. All investigated compounds are the first ternary stannides with rare earth elements and vanadium.

  15. Crystal structure of RCoIn5 (R - Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Y) and R2CoIn8 (R - Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, Y) compounds

    International Nuclear Information System (INIS)

    Kalychak, Ya.M.; Zaremba, V.I.; Baranyak, V.M.; Bruskov, V.A.; Zavalij, P.Yu.

    1989-01-01

    Usng X-ray diffraction method of monocrystal, crystal structure of HoCoIn 5 compound belonging to the HoCoGa 5 structural type is determined. Using the method of powder belonging of CeCoIn 5 structure to the HoCoGa 5 structural type is confirmed. Isostructural compounds with Y, Pr, Nd, Sm, Gd, Tb, Dy are detected. Their lattice periods are determined. Using the method of powder belonging of Ce 2 CoIn 8 compound structure to Ho 2 CoGa 8 structural type is determined. Isostructural compounds with Y, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm are detected and their lattice periods are determined

  16. Specific features of the domain structure of (Gd1-xNdx)2(MoO4)3 crystals

    International Nuclear Information System (INIS)

    Bryzgalov, A.N.; Slepchenko, B.M.; Virachev, B.P.

    1989-01-01

    Formation of the domain structures by sample transfer into thermodynamically metastable state using a simultaneous effect of electric field and temperature change is investigated in Gd 1.7 Nd 0.3 (MoO 4 ) 3 monocrystals (GMO). Some new results obtained under investigations into GMO domain structure using neodymium by means of hydrothermal etching and polarization-optical method are presented

  17. The Gd-Co-Al system at 870/1070 K as a representative of the rare earth-Co-Al family and new rare-earth cobalt aluminides: Crystal structure and magnetic properties

    Science.gov (United States)

    Morozkin, A. V.; Garshev, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Mozharivskyj, Y.; Yuan, Fang; Yao, Jinlei; Nirmala, R.; Quezado, S.; Malik, S. K.

    2018-05-01

    The Gd-Co-Al system has been investigated at 870/1070 K by X-ray and elemental EDS analyses. The existence of the known compounds Gd2Co3Al9 (Y2Co3Ga9-type), Gd3Co4.5Al11.5 (Gd3Co4.6Al11) (Gd3Ru4Al12-type), Gd3Co6-7.4Al3-1.6 (CeNi3-type), GdCo1.15-0.65Al0.85-1.35 (MgZn2-type), Gd2Co2Al (Mo2NiB2-type) and Gd3Co3.5-3.25Al0.5-0.75 (W3CoB3-type) has been confirmed at 870/1070 K. Structure types have been determined for Gd2Co6Al19 (U2Co6Al19-type), Gd7Co6Al7 (Pr7Co6Al7-type), Gd6Co2-2.21Al1-0.79 (Ho6Co2Ga-type) and Gd14Co3.2Al2.8 (Gd14Co2.58Al3.42 at 970 K) (Lu14Co3In3-type). The structures of Gd6Co2Al, Gd6Co2.21Al0.79 and Gd14Co2.58Al3.42 flux-grown at 970 K have been refined from the single crystal X-ray diffraction data. Additionally, new ternary compounds Gd2Co5.7-5.3Al1.3-1.7 (Er2Co7-type) and Gd58Co20Al22 (unknown type structure) have been identified. Quasi-binary solid solutions were detected for Gd2Co17, GdCo5, Gd2Co7, GdCo3, GdCo2 and GdAl2 at 870/1070 K, while no appreciable solubility was observed for the other binary compounds in the Gd-Co-Al system. Magnetic properties of the Gd2Co3Al9, Gd3Co4.6Al11, Gd7Co6Al7, Gd6Co2.2Al0.8 and Gd14Co2.58Al3.42 compounds have been studied and are presented in this work. Gd6Co2.2Al0.8, Gd3Co4.6Al11, Gd7Co6Al7 and Gd14Co2.58Al3.42 order ferromagnetically, while Gd2Co3Al9 displays antiferromagnetic transition. Additionally, {Y, Sm, Tb - Tm}2Co6Al19 (U2Co6Al19-type), Yb2Co3Al9 (Y2Co3Ga9-type), {Y, Sm, Tm, Yb}3Co4.6Al11 (Gd3Ru4Al12-type) and Tb7Co6Al7 (Pr7Co6Al7-type) compounds have been synthesized and investigated.

  18. Gamma multi-detectors and nuclear structure studies: search for superdeformed structures in {sup 147}Gd and {sup 144}Gd isotopes using Crystal Castle; simulation calculations for EUROGAM multi-detector definition; Multidetecteurs gamma et etudes de structure nucleaire: recherche avec le Chateau de Cristal de structures superdeformees dans les isotopes {sup 147}Gd et {sup 144}Gd; calculs de simulation pour la definition du multidetecteur EUROGAM

    Energy Technology Data Exchange (ETDEWEB)

    France, G de

    1992-12-31

    Computer simulations have been used for the calculation of the new generation of 4 {pi}{gamma} multi-detectors (Castle Crystal) of EUROGAM system (phase I and II). Two superdeformed bands (I and II), comprising 16 and 13 transitions respectively, have been described for {sup 147}Gd nucleus during the {sup 122}Sn({sup 30}Si,5n) fusion-evaporation reaction in a 155 MeV bombardment energy. Dynamic inertia momentum similarities and gamma transition energy similarities have been observed between band I and {sup 148}Gd nucleus and between band II and {sup 146}Gd nucleus, respectively. These similarities can be related to a pseudo-spin symmetry. Calculations suggest the existence of an octupolar susceptibility in this mass region. {sup 144}Gd nucleus has been studied using {sup 120}Sn({sup 29}Si,5n) fusion-evaporation reaction in a 155 MeV bombardment energy and using {sup 100}Mo({sup 48}Ti,4n) reactions in a 200 MeV bombardment energy. {gamma}-{gamma} coincidences have revealed the existence of a 58 keV width valley in the matrix representation compatible with theoretical predictions. In spite of the evidence for about ten transitions during these experiments, no superdeformed structure has been demonstrated for {sup 144}Gd nucleus. (J.S.). 87 refs., 57 figs., 41 tabs.

  19. Synchrotron Based Structural Investigations of Mass-Selected PtxGd Nanoparticles and a Gd/Pt(111) Single Crystal for Electrochemical Oxygen Reduction

    DEFF Research Database (Denmark)

    Pedersen, Anders Filsøe; Velazquez-Palenzuela, Amado Andres; Masini, Federico

    2015-01-01

    . 134, 16476–16479 (2012). 3. Velazquez-Palenzuela, A. et al. The enhanced activity of mass-selected PtxGd nanoparticles for oxygen electroreduction. J. Catal. [in press] (2015). doi:10.1016/j.jcat.2014.12.012 4. Perez-Alonso, F. J. et al. The Effect of Size on the Oxygen Electroreduction Activity...

  20. Structure and thermal expansion of Ca9Gd(VO4)7: A combined powder-diffraction and dilatometric study of a Czochralski-grown crystal

    Science.gov (United States)

    Paszkowicz, Wojciech; Shekhovtsov, Alexei; Kosmyna, Miron; Loiko, Pavel; Vilejshikova, Elena; Minikayev, Roman; Romanowski, Przemysław; Wierzchowski, Wojciech; Wieteska, Krzysztof; Paulmann, Carsten; Bryleva, Ekaterina; Belikov, Konstantin; Fitch, Andrew

    2017-11-01

    Materials of the Ca9RE(VO4)7 (CRVO) formula (RE = rare earth) and whitlockite-related structures are considered for applications in optoelectronics, e.g., in white-light emitting diodes and lasers. In the CRVO structure, the RE atoms are known to share the site occupation with Ca atoms at two or three among four Ca sites, with partial occupancy values depending on the choice of the RE atom. In this work, the structure and quality of a Czochralski-grown crystal of this family, Ca9Gd(VO4)7 (CGVO), are studied using X-ray diffraction methods. The room-temperature structure is refined using the powder diffraction data collected at a high-resolution synchrotron beamline ID22 (ESRF, Grenoble); for comparison purposes, a laboratory diffraction pattern was collected and analyzed, as well. The site occupancies are discussed on the basis of comparison with literature data of isostructural synthetic crystals of the CRVO series. The results confirm the previously reported site-occupation scheme and indicate a tendency of the CGVO compound to adopt a Gd-deficient composition. Moreover, the thermal expansion coefficient is determined for CGVO as a function of temperature in the 302-1023 K range using laboratory diffraction data. Additionally, for CGVO and six other single crystals of the same family, thermal expansion is studied in the 298-473 K range, using the dilatometric data. The magnitude and anisotropy of thermal expansion, being of importance for laser applications, are discussed for these materials.

  1. New look at magnetism in single-crystal Gd-Y alloys

    International Nuclear Information System (INIS)

    Ito, T.; Legvold, S.; Beaudry, B.J.

    1981-01-01

    Magnetic susceptibility, electrical resistivity, and specific-heat measurements have been made on a number of polycrystalline and single-crystal samples of Gd-rich Gd-Y alloys. It has been found (i) that samples with more than 30 at. % Y exhibit a helical structure phase; (ii) that samples between 10 and 30 at. % Y exhibit two different Curie-Weiss regimes leading to ''double'' ferromagnetism; and (iii) that samples with less than 10 at. % Y have Gd-like behavior

  2. Correlating Structure and Oxygen Reduction Activity on Y/Pt(111) and Gd/Pt(111) Single Crystals

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese; Pedersen, Anders Filsøe; Johansson, Tobias Peter

    2015-01-01

    Polymer Electrolyte Membrane Fuel Cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the Oxygen Reduction Reaction (ORR) at the PEMFC cathode prevents the commercialisation of this tech......Polymer Electrolyte Membrane Fuel Cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the Oxygen Reduction Reaction (ORR) at the PEMFC cathode prevents the commercialisation...... of this technology. Improving the activity of Pt by alloying it with other metals could decrease the loading of Pt at the cathode to a level comparable to Pt-group metal loading in internal combustion engines. PtxY and PtxGd exhibit exceptionally high activity for oxygen reduction, both in the polycrystalline form...

  3. Rotational and translational distortions of the crystal structure of the Sr{sub 2}HrRuO{sub 6} (Hr = Ho, Dy, Gd, Eu) complex perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Triana, C.A., E-mail: ctrianae@unal.edu.co [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, A.A. 5997, Bogotá D.C. (Colombia); Landínez Téllez, D.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, A.A. 5997, Bogotá D.C. (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, A.A. 5997, Bogotá D.C. (Colombia)

    2013-05-15

    Sr{sub 2}HrRuO{sub 6} (Hr = Ho, Dy, Gd, Eu) complex perovskites were synthesized through the high-temperature solid-state reaction method, and their crystal structures were analyzed in detail as a function of the Hr-cation ionic radius. Results of powder XRD pattern measurement and Rietveld analysis of the experimental profiles show that the Sr{sub 2}HrRuO{sub 6} compounds crystallize in a monoclinic distorted perovskite-like structure, P2{sub 1}/n (#14) space group, where the unit cell parameters are related to the primitive unit cell a{sub p} by a≈√(2)a{sub p}, b≈√(2)a{sub p} and c ≈ 2a{sub p}. The structures show an alternate distribution of the Ru{sup 5+} (2d: 0.5, 0, 0) and Hr{sup 3+} (2c: 0, 0.5, 0) making up RuO{sub 6} and HrO{sub 6} octahedra alternatively arranged in two interleaving fcc sublattices, where the O(1), O(2), and O(3) ions are localized at the corner of the octahedral, while the Sr{sup 2+} is located at the A-site, occupying the cavities built by the corner-sharing octahedra with Wyckoff position 4e. Due to the existence of mismatched ionic sizes between the ionic radii of the Sr{sub 2}HrRuO{sub 6} compounds, the HrO{sub 6} and RuO{sub 6} octahedra are constrained to tilting around the [111]{sub c}, [001]{sub c}, and [110]{sub c} cubic directions so as to optimize the Sr–O inter-atomic bond lengths, tending to rotate the structure in order to fix the Ru{sup 5+} and Hr{sup 3+} ions on the M′ and M″ sites of the complex perovskites. The cell parameters a, b, and c, the inter-atomic bond angles, the inter-atomic bond lengths, and the tilting angles increase as the Hr-cation ionic radius increases. The mismatch that exists in the Sr{sub 2}HrRuO{sub 6} ionic radius produces a large distortion from the ideal cubic symmetry. The pure perovskite-like phase of Sr{sub 2}HrRuO{sub 6} is thermodynamically and kinetically stable at high temperatures above 1420 K, where it is entirely governed by the average size of the Hr{sup 3+} and Ru

  4. Rotational and translational distortions of the crystal structure of the Sr2HrRuO6 (Hr = Ho, Dy, Gd, Eu) complex perovskites

    International Nuclear Information System (INIS)

    Triana, C.A.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2013-01-01

    Sr 2 HrRuO 6 (Hr = Ho, Dy, Gd, Eu) complex perovskites were synthesized through the high-temperature solid-state reaction method, and their crystal structures were analyzed in detail as a function of the Hr-cation ionic radius. Results of powder XRD pattern measurement and Rietveld analysis of the experimental profiles show that the Sr 2 HrRuO 6 compounds crystallize in a monoclinic distorted perovskite-like structure, P2 1 /n (#14) space group, where the unit cell parameters are related to the primitive unit cell a p by a≈√(2)a p , b≈√(2)a p and c ≈ 2a p . The structures show an alternate distribution of the Ru 5+ (2d: 0.5, 0, 0) and Hr 3+ (2c: 0, 0.5, 0) making up RuO 6 and HrO 6 octahedra alternatively arranged in two interleaving fcc sublattices, where the O(1), O(2), and O(3) ions are localized at the corner of the octahedral, while the Sr 2+ is located at the A-site, occupying the cavities built by the corner-sharing octahedra with Wyckoff position 4e. Due to the existence of mismatched ionic sizes between the ionic radii of the Sr 2 HrRuO 6 compounds, the HrO 6 and RuO 6 octahedra are constrained to tilting around the [111] c , [001] c , and [110] c cubic directions so as to optimize the Sr–O inter-atomic bond lengths, tending to rotate the structure in order to fix the Ru 5+ and Hr 3+ ions on the M′ and M″ sites of the complex perovskites. The cell parameters a, b, and c, the inter-atomic bond angles, the inter-atomic bond lengths, and the tilting angles increase as the Hr-cation ionic radius increases. The mismatch that exists in the Sr 2 HrRuO 6 ionic radius produces a large distortion from the ideal cubic symmetry. The pure perovskite-like phase of Sr 2 HrRuO 6 is thermodynamically and kinetically stable at high temperatures above 1420 K, where it is entirely governed by the average size of the Hr 3+ and Ru 5+ cations. Highlights: ► Crystal structure of Sr 2 HrRuO 6 (Hr = Ho, Dy, Gd, Eu) as a function of Hr ionic radius. ► XRD

  5. Synthesis, crystal structure and photoluminescent properties of Eu{sup 3+} ion-activated R{sub 4}MoO{sub 9} (R = Y, Gd, and Lu)

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huaiyong [Department of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Moon, Byung Kee; Choi, Byung Chun [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of); Jeong, Jung Hyun, E-mail: jhjeong@pknu.ac.kr [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of); Yang, Hyun Kyoung [Jeju Global Research Center, Korea Institute of Energy Research, Jeju 695-971 (Korea, Republic of); Jang, Kiwan; Lee, Ho Sueb [Department of Physics, Changwon National University, Changwon 641-773 (Korea, Republic of); Yi, Soung Soo [Department of Electronic Material Engineering, Silla University, Busan 617-736 (Korea, Republic of)

    2013-05-15

    Rare earth molybdates R{sub 4}MoO{sub 9} (R = Y, Gd, and Lu) with Eu{sup 3+} ion-doped were synthesized by solid-state reaction. The phase structure, optical absorption and photoluminescence properties of the as-prepared powder samples were studied. The powder X-ray diffraction patterns indicated that all the compounds crystallized in a hexagonal structure, and the lattice parameters reduced in the order of the ionic radii of R. The UV–visible diffuse reflectance spectra revealed that the compounds had a strong absorption of near-UV light due to the excitation of MoO{sub 6} groups in the host lattices. The energy absorbed by the host lattices could then be transferred to doped Eu{sup 3+} ions, resulting in red emission due to the f–f transitions of Eu{sup 3+} ions. The optical absorption and photoluminescence properties of the compounds indicated that they might be candidates as the color-conversion red phosphors for solid-state lighting. - Highlights: ► Structure, optical and photoluminescence properties of Eu{sup 3+} ion-activated R{sub 4}MoO{sub 9} were studied. ► Energy transfer from MoO{sub x} to Eu{sup 3+} can be used to convert near-UV to red light. ► R{sub 4}MoO{sub 9}:Eu might be candidate for color-conversion red phosphors excited by near-UV light.

  6. Peculiarities of component interaction in {l_brace}Gd, Er{r_brace}-V-Sn Ternary systems at 870 K and crystal structure of RV{sub 6}Sn{sub 6} stannides

    Energy Technology Data Exchange (ETDEWEB)

    Romaka, L., E-mail: romakal@franko.lviv.ua [Inorganic Chemistry Department, Ivan Franko Lviv National University, Kyryla and Mefodiya str. 6, 79005 Lviv (Ukraine); Stadnyk, Yu. [Inorganic Chemistry Department, Ivan Franko Lviv National University, Kyryla and Mefodiya str. 6, 79005 Lviv (Ukraine); Romaka, V.V. [Department of Materials Engineering and Applied Physics, Lviv Polytechnic National University, Ustyyanovycha Str. 5, 79013 Lviv (Ukraine); Demchenko, P.; Stadnyshyn, M.; Konyk, M. [Inorganic Chemistry Department, Ivan Franko Lviv National University, Kyryla and Mefodiya str. 6, 79005 Lviv (Ukraine)

    2011-09-08

    Highlights: > {l_brace}Gd, Er{r_brace}-V-Sn ternary systems at 870 K are characterized by formation of stannides with general compositions RV{sub 6}Sn{sub 6}. > Isostructural RV{sub 6}Sn{sub 6} compounds were also found with Y, Dy, Ho, Tm, and Lu. > The crystal structure of RV{sub 6}Sn{sub 6} compounds was determined by powder diffraction method. > Structural analysis showed that RV{sub 6}Sn{sub 6} compounds (R = Gd, Dy-Tm, Lu) are disordered; YV{sub 6}Sn{sub 6} is characterized by structure ordering. - Abstract: The phase equilibria in the Gd-V-Sn and Er-V-Sn ternary systems were studied at 870 K by means of X-ray and metallographic analyses in the whole concentration range. Both Gd-V-Sn and Er-V-Sn systems are characterized by formation of one ternary compound at investigated temperature, with stoichiometry RV{sub 6}Sn{sub 6} (SmMn{sub 6}Sn{sub 6}-type, space group P6/mmm, a = 0.55322(3) nm, c = 0.91949(7) nm for Gd, a = 0.55191(2) nm, c = 0.91869(8) nm for Er). Solubility of the third component in the binary compounds was not observed. Compounds with the SmMn{sub 6}Sn{sub 6}-type were also found with Dy, Ho, Tm, and Lu, while YV{sub 6}Sn{sub 6} compound crystallizes in HfFe{sub 6}Ge{sub 6} structure type. All investigated compounds are the first ternary stannides with rare earth elements and vanadium.

  7. The Gd14Ag51 structure type and its relation to some complex amalgam structures

    International Nuclear Information System (INIS)

    Tambornino, Frank; Sappl, Jonathan; Hoch, Constantin

    2015-01-01

    Highlights: • The Gd 14 Ag 51 structure type has been revisited on the basis of single crystal diffraction data. • Symmetry analysis from electron density and TEM shows the space group P6/m to be true. • Gd 14 Ag 51 shows good metallic behaviour. • Structure relations to alkali, alkaline-earth and rare-earth metal amalgams can be established. • Complexity values for the RE 14 Ag 51 structure family were calculated. - Abstract: A plethora of binary and ternary intermetallic compounds has been assigned to the Gd 14 Ag 51 structure type, crystallising in the hexagonal system (space group P6/m, a = 1264.30(18) pm, c = 933.58(11) pm for Gd 14 Ag 51 ). Starting in the late 1960s, much work has been invested in the structural elucidation of these crystal structures. However, reliable single crystal data are scarce, and most structure type assignments have been performed merely on the basis of powder data. We have redetermined four representatives of the binary RE 14 Ag 51 structure type (RE = Y, Ce, Gd, Tb) with modern high-precision single crystal X-ray methods. The assignment of the Gd 14 Ag 51 structure type to space group P6/m was additionally verified by careful analysis of high resolution transmission electron micrographs. We emphasise the close relation of the Gd 14 Ag 51 structure type to the structures of some recently described amalgams of similar composition focussing on disorder phenomena and structural complexity. Furthermore, we provide detailed information on synthesis as well as electrical and magnetic properties for Gd 14 Ag 51 , the parent compound of this structure family

  8. Synthesis and crystal structure of K{sub 2}NiF{sub 4}-type novel Gd{sub 1+x}Ca{sub 1−x}AlO{sub 4−x}N{sub x} oxynitrides

    Energy Technology Data Exchange (ETDEWEB)

    Masubuchi, Yuji, E-mail: yuji-mas@eng.hokudai.ac.jp; Hata, Tomoyuki; Motohashi, Teruki; Kikkawa, Shinichi

    2014-01-05

    Highlights: • Novel gadolinium calcium aluminum oxynitride was prepared by solid state reaction. • Crystal structure of the oxynitride was refined by using synchrotron X-ray diffraction. • Gd{sub 1.2}Ca{sub 0.8}AlO{sub 3.8}N{sub 0.2} has a layered K{sub 2}NiF{sub 4}-type structure with the I4mm space group. • Nitride ions preferentially occupy the apical site of aluminum octahedron. -- Abstract: Novel gadolinium calcium aluminum oxynitrides, Gd{sub 1+x}Ca{sub 1−x}AlO{sub 4−x}N{sub x}, were prepared in x = 0.15–0.25 by the solid state reaction of a nitrogen–rich mixture with AlN as an aluminum source; the mixture was sintered twice at 1500 °C for 5 h under 0.5 MPa of nitrogen gas. Shift in the optical absorption edge was observed in their diffuse reflectance spectra from 4.46 eV for the oxide (x = 0) to 2.94 eV for the oxynitride at x = 0.2. The crystal structure of Gd{sub 1.2}Ca{sub 0.8}AlO{sub 3.8}N{sub 0.2} at x = 0.2 was refined using a synchrotron X-ray diffraction data as a layered K{sub 2}NiF{sub 4}-type structure with the I4mm space group. Longer Al–O/N bond lengths in the oxynitride than those in GdCaAlO{sub 4} suggest that the nitride ions are in the apical site of aluminum polyhedron, similar to those in Nd{sub 2}AlO{sub 3}N.

  9. CW laser properties of Nd:GdYAG, Nd:LuYAG, and Nd:GdLuAG mixed crystals

    Science.gov (United States)

    Di, J. Q.; Xu, X. D.; Li, D. Z.; Zhou, D. H.; Wu, F.; Zhao, Z. W.; Xu, J.; Tang, D. Y.

    2011-10-01

    Three mixed crystals, Nd:GdYAG, Nd:LuYAG, and Nd:GdLuAG, were grown by Czochralski method. We report the continuous-wave (CW) Nd:GdYAG, Nd:LuYAG, and Nd:GdLuAG laser operation under laser diode pumping. The maximum output powers are 4.11, 5.31, and 7.47 W, with slope efficiency of 73.0, 55.3, and 57.1%, respectively. With replacing Lu3+ or Y3+ ions with large Gd3+ ions, the pump efficiency increases.

  10. Crystal growth, structure, defects, mechanical and spectral properties of Nd{sub 0.01}:Gd{sub 0.89}La{sub 0.1}NbO{sub 4} mixed crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Shoujun; Lu, Wancheng; Xu, Jinrui [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui Province (China); University of Science and Technology of China, Hefei (China); Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Sun, Guihua; Sun, Dunlu [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui Province (China)

    2017-10-15

    A novel mixed laser crystal of Nd:GdLaNbO{sub 4} (Nd:GLNO) was grown successfully by conventional Czochralski method. The unit cell parameters were obtained by Rietveld refinement method. The density of the as-grown crystal was measured by Archimedean buoyancy method and calculated in theory. Absorption spectrum of Nd:GLNO crystal was recorded at room temperature, and 11 absorption peaks were assigned. The defects of Nd:GLNO crystal were revealed by using chemical etching method with phosphoric acid as etchant. The mechanical properties (including hardness, yield strength, elastic stiffness constant, fracture toughness and brittleness index) were systemically estimated based on Vickers hardness test. All these obtained results play a quite important role in further investigation of Nd:GLNO crystal. (orig.)

  11. Unoccupied surface electronic structure of Gd(0001)

    International Nuclear Information System (INIS)

    Li, D.; Dowben, P.A.; Ortega, J.E.; Himpsel, F.J.

    1994-01-01

    The unoccupied surface electronic structure of Gd(0001) was investigated with high-resolution inverse-photoemission spectroscopy. An empty surface state near E F is observed at bar Γ. Two other surface-sensitive features are also revealed at 1.2 and 3.1 eV above the Fermi level. Hydrogen adsorption on Gd surfaces was used to distinguish the surface-sensitive features from the bulk features. The unoccupied bulk-band critical points are determined to be Γ 3 + at 1.9 eV and A 1 at 0.8 eV

  12. Syntheses and crystal structures of BaAgTbS{sub 3}, BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Jai; Beard, Jessica C.; Ibers, James A. [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113 (United States); Mesbah, Adel [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113 (United States); ICSM-UMR 5257 CNRS/CEA/UM2/ENSCM, Bat 426, BP 17171, 30207 Bagnols/Ceze (France)

    2015-06-15

    Five new quaternary chalcogenides of the 1113 family, namely BaAgTbS{sub 3}, BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3}, were synthesized by the reactions of the elements at 1173-1273 K. For CsAgUTe{sub 3} CsCl flux was used. Their crystal structures were determined by single-crystal X-ray diffraction studies. The sulfide BaAgTbS{sub 3} crystallizes in the BaAgErS{sub 3} structure type in the monoclinic space group C{sup 3},{sub 2h}-C2/m, whereas the tellurides BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3} crystallize in the KCuZrS{sub 3} structure type in the orthorhombic space group D{sup 1},{sub 2}{sup 7},{sub h}-Cmcm. The BaAgTbS{sub 3} structure consists of edge-sharing [TbS{sub 6}{sup 9-}] octahedra and [AgS{sub 5}{sup 9-}] trigonal pyramids. The connectivity of these polyhedra creates channels that are occupied by Ba atoms. The telluride structure features {sup 2}{sub ∞}[MLnTe{sub 3}{sup 2-}] layers for BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and {sup 2}{sub ∞}[AgUTe{sub 3}{sup 1-}] layers for CsAgUTe{sub 3}. These layers comprise [MTe{sub 4}] tetrahedra and [LnTe{sub 6}] or [UTe{sub 6}] octahedra. Ba or Cs atoms separate these layers. As there are no short Q..Q (Q = S or Te) interactions these compounds achieve charge balance as Ba{sup 2+}M{sup +}Ln{sup 3+}(Q{sup 2-}){sub 3} (Q = S and Te) and Cs{sup +}Ag{sup +}U{sup 4+}(Te{sup 2-}){sub 3}. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Experiment and density functional theory analyses of GdTaO4 single crystal

    Science.gov (United States)

    Ding, Shoujun; Kinross, Ashlie; Wang, Xiaofei; Yang, Huajun; Zhang, Qingli; Liu, Wenpeng; Sun, Dunlu

    2018-05-01

    GdTaO4 is a type of excellent materials that can be used as scintillation, laser matrix as well as self-activated phosphor has generated significant interest. Whereas its band structure, electronic structure and optical properties are still need elucidation. To solve this intriguing problem, high-quality GdTaO4 single crystal (M-type) was grown successfully using Czochralski method. Its structure as well as optical properties was determined in experiment. Moreover, a systematic theoretical calculation based on the density function theory methods were performed on M-type and M‧-type GdTaO4 and their band structure, density of state as well as optical properties were obtained. Combine with the performed experiment results, the calculated results were proved with high reliability. Hence, the calculated results obtained in this work could provide a deep understanding of GdTaO4 material, which also useful for the further investigation on GdTaO4 material.

  14. Peculiar features of thermal emission of GdB4 and GdB6 single crystals

    International Nuclear Information System (INIS)

    Ostrovskij, E.K.; Taran, A.A.; Kovalev, A.V.; Tkachenko, V.F.; Dudnik, E.M.; Matvienko, A.A.

    1990-01-01

    Thermoemission parameters of single crystals (410) GdB 4 and (110) GdB 6 are studied. Work function is calculated by total current. It is stated that work function of GdB 6 within temperature range of 1500-1880 K after 80 h of annealing varies from 2.95 to 3.10 eV practically with the same temperature coefficient as GdB 4 , i.e. 4.1x10 -4 eV/K. It is shown that single crystal gadolinium hexaboride during the high-temperature annealing in the surface region (∼70 mm) is transformed into gadolinium tetraboride. Influence of free air has been first studied on the GdB 4 emissivity which is determined to increase to p=1.3x10 -2 Pa within the range of T=1640-1840 K

  15. Thermal, defects, mechanical and spectral properties of Nd-doped GdNbO{sub 4} laser crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Shoujun [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China); University of Science and Technology of China, Hefei (China); Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Wang, Xiaofei; Sun, Guihua; Li, Xiuli; Sun, Dunlu [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China)

    2017-05-15

    A Nd-doped GdNbO{sub 4} crystal was grown successfully by Czochralski method. Its monoclinic structure was determined by X-ray diffraction; the unit-cell parameters are a = 5.38 Aa, b = 11.09 Aa, c = 5.11 Aa, and β = 94.56 . The morphological defects of Nd:GdNbO{sub 4} crystal were investigated using the chemical etching with the phosphoric acid etchant. For a new crystal, the physical properties are of great importance. The hardness and density of Nd:GdNbO{sub 4} were investigated first. Thermal properties of Nd:GdNbO{sub 4}, including thermal expansion coefficient and specific heat, were measured along a-, b-, and c-crystalline axes. Thermal properties indicate that the Nd:GdNbO{sub 4} pumped along c-axis can reduce the thermal lensing effect effectively. The specific heat is 0.53 J g{sup -1} K{sup -1} at 300 K, indicating a relatively high damage threshold of Nd:GdNbO{sub 4}. The transmission and emission spectrum of Nd:GdNbO{sub 4} were measured, and the absorption peaks were assigned. The strongest emission peak of Nd:GdNbO{sub 4} is located at 1065.3 nm in the spectral range of 850-1420 nm excited by 808 nm laser. The refractive index of Nd:GdNbO{sub 4} was calculated with the transmission spectrum and fitted with Sellmeier equation. All these obtained results is of great significance for the further research of Nd:GdNbO{sub 4}. (orig.)

  16. Experimental and theoretical study of pure and doped crystals: Gd2O2S, Gd2O2S:Eu3+ and Gd2O2S:Tb3+

    Science.gov (United States)

    Wang, Fei; Chen, Xiumin; Liu, Dachun; Yang, Bin; Dai, Yongnian

    2012-08-01

    Quantum chemistry and experimental method were used to study on pure and doped Gd2O2S crystals in this paper. The band structure and DOS diagrams of pure and doped Gd2O2S crystals which calculated by using DFT (Density Functional Theory) method were illustrated to explain the luminescent properties of impurities in crystals. The calculations of the crystal structure were finished by using the program of CASTEP (Cambridge Sequential Total Energy Package). The samples showed the characteristic emissions of Tb3+ ions with 5D4-7FJ transitions and Eu3+ ions with 5D0-7FJ transitions which emit pure green luminescence and red luminescence respectively. The experimental excitation spectra of Tb3+ and Eu3+ doped Gd2O2S are in agreement of the DOS diagrams over the explored energy range, which has allowed a better understanding of different luminescence mechanisms of Tb3+ and Eu3+ in Gd2O2S crystals.

  17. The Gd{sub 14}Ag{sub 51} structure type and its relation to some complex amalgam structures

    Energy Technology Data Exchange (ETDEWEB)

    Tambornino, Frank; Sappl, Jonathan; Hoch, Constantin, E-mail: constantin.hoch@cup.uni-muenchen.de

    2015-01-05

    Highlights: • The Gd{sub 14}Ag{sub 51} structure type has been revisited on the basis of single crystal diffraction data. • Symmetry analysis from electron density and TEM shows the space group P6/m to be true. • Gd{sub 14}Ag{sub 51} shows good metallic behaviour. • Structure relations to alkali, alkaline-earth and rare-earth metal amalgams can be established. • Complexity values for the RE{sub 14}Ag{sub 51} structure family were calculated. - Abstract: A plethora of binary and ternary intermetallic compounds has been assigned to the Gd{sub 14}Ag{sub 51} structure type, crystallising in the hexagonal system (space group P6/m, a = 1264.30(18) pm, c = 933.58(11) pm for Gd{sub 14}Ag{sub 51}). Starting in the late 1960s, much work has been invested in the structural elucidation of these crystal structures. However, reliable single crystal data are scarce, and most structure type assignments have been performed merely on the basis of powder data. We have redetermined four representatives of the binary RE{sub 14}Ag{sub 51} structure type (RE = Y, Ce, Gd, Tb) with modern high-precision single crystal X-ray methods. The assignment of the Gd{sub 14}Ag{sub 51} structure type to space group P6/m was additionally verified by careful analysis of high resolution transmission electron micrographs. We emphasise the close relation of the Gd{sub 14}Ag{sub 51} structure type to the structures of some recently described amalgams of similar composition focussing on disorder phenomena and structural complexity. Furthermore, we provide detailed information on synthesis as well as electrical and magnetic properties for Gd{sub 14}Ag{sub 51}, the parent compound of this structure family.

  18. Growth of multiferroic Gd1-xYxMnO3 single crystals by optical floating zone technique

    International Nuclear Information System (INIS)

    Sarguna, R.M.; Ganesamoorthy, S.; Sridharan, V.; Subramanian, N.

    2014-01-01

    Rare earth manganites RMnO 3 with distorted perovskite structure are excellent multiferroic materials. The discovery of magnetic spin driven ferroelectricity in orthorhombic manganites (TbMnO 3 ) has sparked a surge in research into understanding the fundamental mechanism of multiferroic behavior. These systems fall under the category of type-2 multiferroics, the change of spatially modulated magnetic moment from sinusoidal to cycloidal gives rise to electric polarization. The magnetic structure depends upon the Mn-O-Mn bond angle. GdMnO 3 shows multiferroic properties only in the presence of applied magnetic field. When a magnetic field is applied along the b-axis, GdMnO 3 enters a ferroelectric state with an electric polarisation along the c-axis. By altering the Mn-O-Mn angle it is expected that GdMnO 3 will show multiferroic property even in the absence of magnetic field like TbMnO 3 . To alter the Mn-O-Mn bond angle GdMnO 3 was substituted with Y having lower ionic radius at Gd site. The effect of Y doping at the rare-earth site in GdMnO 3 investigated on polycrystalline samples of Gd 1-x Y x MnO 3 demonstrated a magneto-electric coupling in x=0.1-0.4. Single crystals are expected to give much amplified signal in respect of ferroelectric and magnetic properties. In this work we have grown Y substituted Gd 1-x Y x MnO 3 (x = 0.2, 0.3 and 0.4) by optical floating zone technique under different gas atmosphere. Growth rate of 1-2 mm/h yielded crack free crystals. Quality of the crystals was checked using Laue diffraction. Effect of growth rate and atmosphere pressure will be presented in this talk. (author)

  19. Novel chromium doped perovskites A{sub 2}ZnTiO{sub 6} (A = Pr, Gd): Synthesis, crystal structure and photocatalytic activity under simulated solar light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Hekai [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Fang, Minghao, E-mail: fmh@cugb.edu.cn [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Huang, Zhaohui, E-mail: huang118@cugb.edu.cn [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Liu, Yan’gai [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Chen, Kai [National Engineering Research Center for Rare Earth Materials, General Research Institute For Nonferrous Metals, Grirem Advanced Materials Co.,Ltd., Beijing 100088 (China); Guan, Ming; Tang, Chao; Zhang, Lina; Wang, Meng [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China)

    2017-01-30

    Highlights: • Novel Cr doped A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) photocatalysts were successfully synthesized. • The light absorbance and photocatalytic activity are enhanced through Cr doping. • The photocatalytic reaction mechanism of these photocatalyst was investigated. - Abstract: Double perovskite related oxides A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) have been successfully synthesized by solid state reaction and investigated as photocatalysts for the first time. The two layered titanates mainly demonstrate absorbances under UV irradiation, except for several sharp absorption bands above 400 nm for Pr{sub 2}ZnTiO{sub 6}. Therefore, a series of photocatalysts by doping A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) with Cr have been developed in the hope to improve their absorption in the visible light region. The successful incorporation of Cr was detected by XRD and XPS, and the prepared samples have also been characteriazed by SEM, UV–vis DRS and PL. The characterization results suggested that Cr was present mainly in the form of Cr3+, with only a small amount of Cr6+ species. It served as an efficient dopant for the extension of visible light absorbance and improved photocatalytic activities under solar light irradiation. For both Pr{sub 2}ZnTiO{sub 6} and Gd{sub 2}ZnTiO{sub 6}, the valence band (VB) was composed of hybridized states of the Zn 3d, O 2p and the conduction band (CB) has major contribution from Zn 4s, Ti 3d orbitals. For Cr doped samples, the newly formed spin-polarized valence band in the middle of the band gap that primarily arises from Cr 3d orbitals was responsible for the improved optical and photocatalytic properties.

  20. Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivity

    KAUST Repository

    Pramana, Stevin S.

    2017-12-04

    A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

  1. Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivity

    KAUST Repository

    Pramana, Stevin S.; Cavallaro, Andrea; Li, Cheng; Handoko, Albertus D.; Chan, Kuang Wen; Walker, Robert J.; Regoutz, Anna; Herrin, Jason S.; Yeo, Boon Siang; Payne, David J.; Kilner, John A.; Ryan, Mary P.; Skinner, Stephen J.

    2017-01-01

    A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

  2. Magnetic properties of the tetragonal RCuGa{sub 3} (R=Pr, Nd and Gd) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Nagalakshmi, R., E-mail: nagaphys@yahoo.com [Department of Physics, National Institute of Technology, Tiruchirappalli 6200015 (India); Kulkarni, Ruta; Dhar, S.K.; Thamizhavel, A. [DCMPMS, Tata Institute of Fundamental Research, Mumbai 400005 (India); Krishnakumar, V. [Department of Physics, Periyar University, Salem 636011 (India); Reiffers, Marian; Čurlík, Ivan [Institute of Experimental Physics, Watsonova 47, SK-040 01 Kosice (Slovakia); Department of Physics, University of Presov, 17 Novembra 1, SK-080 01 (Slovakia); Hagemann, Hans; Lovy, Dominique [Department of Physical Chemistry, University of Geneva, Geneva (Switzerland); Nallamuthu, S. [Department of Physics, National Institute of Technology, Tiruchirappalli 6200015 (India)

    2015-07-15

    Single crystals of tetragonal RCuGa{sub 3} (R=La, Pr, Nd and Gd), with BaNiSn{sub 3} type structure (space group I4 mm), have been grown by high temperature solution growth technique using Ga as flux. Their magnetic properties were determined by heat capacity and the measurement of magnetization and electrical resistivity along [100] and [001] directions. Except LaCuGa{sub 3}, the compounds order magnetically. PrCuGa{sub 3} undergoes a ferromagnetic transition with Curie temperature of 4.6 K. NdCuGa{sub 3} shows a bulk magnetic transition at 3.3 K. The data on GdCuGa{sub 3} indicate combined characteristics of spin glass and antiferromagnetic behavior at low temperatures. From the Schottky heat capacity data the crystal electric field level energy spectra have been determined. Further we have performed temperature dependent measurements of electron spin resonance (ESR) on GdCuGa{sub 3} between 11 K and room temperature. The ESR data indicate an enhancement of magnetic fluctuations associated with spin reorientation and both homogeneous and inhomogeneous thermal broadening of the linewidth. - Highlights: • RCuGa{sub 3} (R=La, Pr, Nd and Gd) single crystals were grown by flux technique. • The compounds exhibit long range magnetic ordering. • Crystal electric field levels have been derived from Schottky heat capacity. • Electron spin resonance (ESR) studies of GdCuGa{sub 3} are also discussed.

  3. Hyperfine structure in the Gd II spectrum and the nuclear electric quadrupole moment of 157Gd

    International Nuclear Information System (INIS)

    Clieves, H.P.; Steudel, A.

    1979-01-01

    The hyperfine structure of 157 Gd was investigated in 20 Gd II lines by means of a photoelectric recording Fabry-Perot interferometer with digital data processing. The hyperfine splitting factors, A and B, were obtained by computer fits to the observed line structures. Using a multiconfigurational set of wave functions in intermediate coupling derived by Wyart, mono-electronic parameters were deduced by a parametric treatment. The nuclear electric quadrupole moment of 157 Gd was evaluated from the quadrupole interaction of the 5d electron in 4f 7 5d6s, the 5d electron in 4f 7 5d6p, and the 6p electron in 4f 7 5d6p. The three values obtained for the quadrupole moment agree very well. The final result, corrected for Sternheimer shielding, is Q( 157 Gd) = 1.34(7) x 10 -24 cm 2 . (orig.) [de

  4. Achieving a table-like magnetocaloric effect and large refrigerant capacity in in situ multiphase Gd65Mn25Si10 alloys obtained by crystallization treatment

    International Nuclear Information System (INIS)

    Shen, X Y; Zhong, X C; Huang, X W; Mo, H Y; Feng, X L; Liu, Z W; Jiao, D L

    2017-01-01

    In situ multiphase structure Gd 65 Mn 25 Si 10 alloys were fabricated by melt spinning and subsequent crystallization treatment. In the process of crystallization, the α -Gd, GdMn 2 and Gd 5 Si 3 phases precipitate in the amorphous matrix in turn. The Curie temperature ( T C ) values for the α -Gd crystallization phase and amorphous matrix can be tailored by tuning the crystallization treatment time. All three multiphase alloys obtained by crystallization treatment at 637 K for 20, 30 and 40 min, respectively, undergo multiple successive magnetic phase transitions. A table-like magnetic entropy change over a wide temperature range (∼90–120 K) and a large full width at half maximum (Δ T FWHM ) magnetic entropy change (∼230 K) were achieved in the above-mentioned crystallized alloys, resulting in large refrigerant capacities (RCs). The enhanced RCs of the three crystallized alloys for a magnetic field change of 0–5 T are in the range of 541–614 J kg −1 . Large Δ T FWHM and RC values and a table-like (−Δ S M ) max feature obtained in in situ multiphase Gd 65 Mn 25 Si 10 crystallized alloys make them suitable for potential application in efficient Ericsson-cycle magnetic refrigeration working in a temperature range from 74 to 310 K. (paper)

  5. Structural and magnetic properties of Gd1-xPrxMn2Si2 silicides

    International Nuclear Information System (INIS)

    Kilic, A.; Kervan, S.; Gencer, A.

    2004-01-01

    X-ray powder diffraction, AC susceptibility and differential scanning calorimetry (DSC) studies were performed on the polycrystalline Gd 1-x Pr x Mn 2 Si 2 (0≤x≤1) compounds. All compounds investigated crystallize in the body-centred tetragonal ThCr 2 Si 2 -type structure with the space group I4/mmm. Substitution of Pr for Gd leads to a linear increase of the lattice constants and the unit cell volume. The lattice constants and the unit cell volume obey Vegard's law. At the Curie temperature T C (Gd), the Gd sublattice orders and reconfigures the ordering in the Mn sublattice. This temperature becomes depressed and disappears with increasing Pr content x. The Neel temperature T N (Mn) determined by DSC technique decreases linearly with increasing Pr content x. The results are summarized in the x-T magnetic phase diagram

  6. Anomalies of temperature dependence of the upper critical magnetic field of GdBa2Cu3O7-x and their relation with layered crystal structure

    International Nuclear Information System (INIS)

    Anshukova, N.V.; Veselago, V.G.; Golovashkin, A.I.

    1989-01-01

    Temperature dependence of upper critical field H c2 (T) near T c was investigated on polycrystal GdBa 2 Cu 3 O 7-x . The resistive superconductive transitions were measured in magnetic fields up to 15 T. We observed a magnetic-field induced broadening of transition and an appearance of H c2 (T) nonlinearity near T c and explained such effects by the influence of individual grains H c2 anisotropy on the base of the percolation model. Estimated are slopes: for magnetic field along superconductive layers -dH c2 parallel /dT≅ 7T/K and for field across layers -dH c2 tr /dT=0.2 T/K. It was found that H c2 (T)-curves display anomalies in a break form, which were not explained in the percolation model. The across coherence length ξ tr (T) obtained from values of the slopes was comparable with distance d between two superconductive layers. So we think that in this situation a fracture on the H c2 (T)-curves may be explained by the appearance of electronic density nonuniformity and it is precursor of crossover to two-dimensional superconductivity

  7. Structure and magnetic transport properties of GdIn{sub 3−x}Mn{sub x} intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    He, Qiang; Guo, Yongquan, E-mail: yqguo@ncepu.edu.cn; Liu, Hanyuan

    2016-03-01

    The crystal structures and magneto-transport properties of GdIn{sub 3−x}Mn{sub x} have been investigated using X-ray diffraction and magnetic and electric measurements. GdIn{sub 3−x}Mn{sub x} crystallize in cubic structure, and their lattice parameters tend to decrease with increasing Mn content due to the size effect at In site by Mn substitution for In. Mn doped GdIn{sub 3−x}Mn{sub x} order antiferromagnetically at low temperature. However, Mn doping into GdIn{sub 3} causes the decrease of Néel temperature due to the distortion of Gd(In,Mn){sub 3} tetrahedron formed by Gd at corners and (In,Mn) at face centers in unit cell. The resistivities of GdIn{sub 3−x}Mn{sub x} are going up with increasing Mn content. The electric phase transition is associated with the magnetic transition, and the magneto-transport follows electron–magnon scattering model in low temperature region and the Stoner spin fluctuation model in high temperature region, respectively. - Highlights: • Novel GdIn{sub 3−x}Mn{sub x} intermetallic compounds have been successfully prepared. • The lattice parameters tend to decrease with increasing Mn content. • GdIn{sub 3−x}Mn{sub x} orders antiferromagnetically at low temperature. • The strong correlation between the electric transport and magnetic state is observed.

  8. Ab inito calculations of Hubbard parameters for NiO and Gd crystals

    Directory of Open Access Journals (Sweden)

    A. R Faghihi and S Jalali Asadabadi

    2008-07-01

    Full Text Available   In this research the Hubbard parameters have been calculated for NiO and Gd crystals, as two strongly correlated systems with partially full 3d and 4f levels, respectively. The calculations were performed within the density functional theory (DFT using the augmented plane waves plus the local orbitat (APW+lo method. We constructed a suitable supercell and found that the Hubbard parameters for the NiO and Gd compounds are equal to 5.9 eV and 5.7 eV, respectively. Our results are in good agreement with experimental data and results of other computational methods. Then we used the obtained parameters to study the structural properties of NiO and Gd by means of LDA+U approximation. Our results calculated by the LDA+U method which are in better agreement with the experiment show a significant improvement compared to the GGA approximation. The result shows that our method for calculating U parameter can be considered as a satisfactory method to study a strongly correlated system.

  9. Electronic Structure of GdCuGe Intermetallic Compound

    Science.gov (United States)

    Lukoyanov, A. V.; Knyazev, Yu. V.; Kuz'min, Yu. I.

    2018-04-01

    The electronic structure of GdCuGe intermetallic compound has been studied. Spin-polarized energy spectrum calculations have been performed by the band method with allowance for strong electron correlations in the 4 f-shell of gadolinium ions. Antiferromagnetic ordering of GdCuGe at low temperatures has been obtained in a theoretical calculation, with the value of the effective magnetic moment of gadolinium ions reproduced in fair agreement with experimental data. The electronic density of states has been analyzed. An optical conductivity spectrum has been calculated for GdCuGe; it reveals specific features that are analogous to the ones discovered previously in the GdCuSi compound with a similar hexagonal structure.

  10. Crystal growth, spectroscopic and CW laser properties of Nd0.03Lu2.871Gd0.099Al5O12 crystal

    Science.gov (United States)

    Di, J. Q.; Xu, X. D.; Cheng, S. S.; Li, D. Z.; Zhou, D. H.; Wu, F.; Zhao, Z. W.; Xu, J.

    2011-11-01

    Nd0.03Lu2.871Gd0.099Al5O12 (Nd:LuGdAG) crystal was grown by the Czochralski method. The absorption, fluorescence spectra and fluorescence lifetime of Nd:LuGdAG crystal at room temperature were investigated for the first time. We reported the continuous-wave (CW) Nd:LuGdAG laser operation under diode pumping. Output power of 1.43 W at 1064 nm was achieved with a slope efficiency of 34.1%. All the results show that Nd:LuGdAG crystal is a promising laser material.

  11. Influence of Y, Gd and Sm on the glass forming ability and thermal crystallization of aluminum based alloy

    International Nuclear Information System (INIS)

    Aliaga, L.C.R.; Bolfarini, C.; Kiminami, C.S.; Botta Filho, W.J.; Danez, G.P.

    2010-01-01

    Al-based amorphous alloys represent an important family of metals and a great scientific activity has been devoted to determine the main features of both glass forming ability (GFA) and crystallization behavior in order to have a comprehensive framework aimed at potential technological applications. Nowadays, it is well known that the best Al-based amorphous alloys are formed in ternary systems such as Al- RE-TM, where RE is a rare earth and TM a transition metal. This paper presents results of research in Al 85 Ni 10 RE 5 alloys (RE = Y, Gd and Sm). Amorphous ribbons were processed by melt-spinning under the same conditions and subsequently characterized by x-ray diffraction (XRD) and differential scanning calorimetry (DSC). Results show appreciable micro structural differences as function of the rare earth, thus crystal is obtained for Y, nano-glassy for Gd and, fully amorphous structure for Sm. (author)

  12. Czochralski growth and optical properties of Li 6Gd 1-xEu x(BO 3) 3 ( x=0-1) single crystals

    Science.gov (United States)

    Yavetskiy, R. P.; Dolzhenkova, E. F.; Dubovik, M. F.; Korshikova, T. I.; Tolmachev, A. V.

    2005-04-01

    It was shown that a continuous series of Li 6Gd 1-xEu x(BO 3) 3 solid solutions exist within the whole concentration range ( x=0-1). Li 6Gd 1-xEu x(BO 3) 3 ( x=0-0.03; 1) single crystals up to 25 mm in length and up to 20 mm in diameter have been grown by the Czochralski method. The structural perfection of the crystals has been estimated from etch patterns and XPA analysis results. The optical absorption and thermally stimulated luminescence of the grown crystals has been studied.

  13. Calculation of the band structure of GdCo2, GdRh2 e GdIr2 by the APW method

    International Nuclear Information System (INIS)

    Carvalho, J.A.B. de.

    1974-03-01

    The band structure of GdCo 2 , GdRh 2 , GdIr 2 has been calculated by the APW method. A histogram of the density of states is presented for each compound. The bands are transition-metal-like, with s-d hybridization near the Fermi level. The 5d character near the Fermi level increases as one goes from Co to Ir

  14. Growth and optical properties of Tm:GdVO4 single crystal

    International Nuclear Information System (INIS)

    Urata, Y.; Akagawa, K.; Wada, S.; Tashiro, H.; Fukuda, T.

    1999-01-01

    Thulium-doped gadolinium vanadate (Tm:GdVO 4 ) single crystal has been successfully grown by a modified Czochralski (CZ) technique. Effective distribution coefficient of Tm was determined to be 0.74. Absorption characterization was performed in the 800 nm region and the maximum absorption peak was found at 799 nm for π polarization. Fluorescence spectra for tuning at the maximum absorption were obtained around 1.8-2.0 μm region with 100 nm bandwidth. This suggests that a Tm:GdVO 4 crystal is expected as a new promising LD pumped solid-state laser in the 2 μm region. (orig.)

  15. Structural and magnetic properties of Gd{sup 3+} ion substituted magnesium ferrite nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Elkady, Ashraf S. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Department of Reactor Physics, NRC, Atomic Energy Authority, Cairo (Egypt); Hussein, Shaban I. [Department of Reactor Physics, NRC, Atomic Energy Authority, Cairo (Egypt); Rashad, Mohamed M., E-mail: rashad133@yahoo.com [Central Metallurgical Research and Development Institute, Helwan, Cairo 11421 (Egypt)

    2015-07-01

    Nanocrystalline MgGd{sub x}Fe{sub 2−x}O{sub 4} powders (where x=0, 0.05, 0.1, 0.2, 0.25, 0.3) have been synthesized by the ethylene diamine tetraacetic acid (EDTA)-based sol–gel combustion method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM) were applied in order to study the effect of variation of Gd{sup 3+} ion substitution and its impact on crystal structure, crystallite size, lattice parameters, nanostructure and magnetic properties of the formed powders. XRD indicated that, after doping and calcination at 400 °C for 2 h, all samples have two spinel ferrite structures namely cubic and tetragonal phases, which are dependent on Gd{sup 3+} ion concentration. The cubic phase is found to increase with increasing the Gd{sup 3+} ion molar ratio up to 0.1, compared to pure MgFe{sub 2}O{sub 4} and higher Gd{sup 3+} content samples. Indeed, with increasing Gd{sup 3+} ion, the crystallite size was almost unchanged whereas the lattice parameter was found to increase. FT-IR spectrum showed broadening of the ν{sub 2} band and the presence of another band in the range (465–470 cm{sup −1}) upon adding Gd{sup 3+} ion, which confirm the presence of Gd{sup 3+} ion in addition to Fe{sup 3+} ion at octahedral site. Besides, these bands were assigned to the formation of (Gd{sup 3+}–O{sup 2−}) complexes at B-sites. HRTEM images showed that the studied samples consist of nanocrystallites having average particle sizes around 9 nm for pure MgFe{sub 2}O{sub 4} up to 27 and 42 nm for the Gd{sup 3+} ion substituted MgFe{sub 2}O{sub 4} of molar ratio 0.05 and 0.30, respectively. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Gd concentration incorporation up to x=0.1, as a result of the change of cubic and tetragonal spinel ratio and lattice parameters. Meanwhile, the formed powders exhibited

  16. Specific features of the domain structure of (Gd sub 1-x Nd sub x ) sub 2 (MoO sub 4 ) sub 3 crystals. Osobennosti domennoj struktury kristallov (Gd sub 1-x Nd sub x ) sub 2 (MoO sub 4 ) sub 3

    Energy Technology Data Exchange (ETDEWEB)

    Bryzgalov, A N; Slepchenko, B M; Virachev, B P [Cherepovetskij Gosudarstvennyj Pedagogicheskij Inst., Cherepovets (USSR)

    1989-11-01

    Formation of the domain structures by sample transfer into thermodynamically metastable state using a simultaneous effect of electric field and temperature change is investigated in Gd{sub 1.7}Nd{sub 0.3}(MoO{sub 4}){sub 3} monocrystals (GMO). Some new results obtained under investigations into GMO domain structure using neodymium by means of hydrothermal etching and polarization-optical method are presented.

  17. Absorption spectra of CsNd(MoO4)2 and CsGd(MoO4)2-Nd3+ crystals in strong magnetic fields

    International Nuclear Information System (INIS)

    Gorban', I.S.; Kozeeva, L.P.; Slobodyanyuk, A.V.; Shevchenko, V.A.

    1987-01-01

    The comparison of the electronic structure of Nd 3+ in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 - Nd 3+ crystals is made. It is established that in these crystals the activator centers, mainly, of the certain type with the symmetry of the local environment C 2 are formed. The absorption spectra of self-activated CsNd(MoO 4 ) 2 crystal differ from spectra of CsGd(MoO 4 ) 2 - Nd 3+ by the presence of the vibrating structure. The Stark splittings of energy levels of Nd 3+ in the investigated crystalline matrices are more sensitive to the environment effect than the Zeeman ones. The ground state of Nd 3+ ion in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 molybdates is characterized by the similar values of g-factors

  18. Electron spin resonance of Gd in the nuclear cooling agent: PrNi5 single crystals

    International Nuclear Information System (INIS)

    Levin, R.; Davidov, D.; Grayevsky, A.; Shaltiel, D.; Zevin, V.

    1980-01-01

    The ESR of Gd in single crystals of PrNi 5 is observed to exhibit significant angular dependence of the resonance position and linewidth at low temperatures. This is interpreted in terms of the axial spin Hamiltonian which takes the anisotropic susceptibility and the Gd-Pr exchange into consideration. From lineshape analysis the axial crystal field parameter and isotropic Gd-Pr exchange are derived. The Gd ESR linewidth increases with temperature; the thermal broadening is angularly dependent. This is similar to that observed for the Pr NMR in PrNi 5 single crystals. Both the NMR and ESR thermal broadenings are attributed to low-frequency fluctuations of the Pr ions induced by the Pr-Pr exchange coupling. A model for hexagonal Van-Vleck compounds is given and with the linewidth enables the Pr-Pr exchange coupling, under the assumption of a Gaussian or a Lorenzian distribution of the low-frequency fluctuation spectra, to be extracted. It is suggested that the angular dependence of the ESR thermal broadening is due to the Gd-Pr exchange coupling. (UK)

  19. Optical properties and radiation response of Ce3+-doped GdScO3 crystals

    International Nuclear Information System (INIS)

    Yamaji, Akihiro; Fujimoto, Yutaka; Futami, Yoshisuke; Yokota, Yuui; Kurosawa, Shunsuke; Kochurikhin, Vladimir; Yanagida, Takayuki; Yoshikawa, Akira

    2012-01-01

    10%-Ce doped GdScO 3 perovskite type single crystal was grown by the Czochralski process. The Ce concentration in the crystal was measured. No impurity phases were observed by powder X-ray diffraction analysis. We evaluated the optical and radiation properties of the grown crystal. Ce:GdScO 3 crystal showed photo- and radio-luminescence peaks due to Ce 3+ of 5d-4f transition and colour centre. The photoluminescence decay time was sub-ns order. The relative light yield under 5.5 MeV alpha-ray excitation was calculated to be approximately 9% of BGO. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Lanthanide 4f-level location in AVO4:Ln3+ (A = La, Gd, Lu) crystals

    NARCIS (Netherlands)

    Krumpel, A.H.; Van der Kolk, E.; Cavalli, E.; Boutinaud, P.; Bettinelli, M.; Dorenbos, P.

    2009-01-01

    The spectral properties of LaVO4, GdVO4 and LuVO4 crystals doped with Ce3+, Pr3+, Eu3+ or Tb3+ have been investigated in order to determine the position of the energy levels relative to the valence and conduction bands of the hosts along the trivalent and divalent lanthanide series. Pr3+ and Tb3+

  1. Structural and electronic behavior of Sr2GdRuO6 complex perovskite

    International Nuclear Information System (INIS)

    Corredor, L.T.; Velasco Zarate, J.; Landinez Tellez, D.A.; Fajardo, F.; Arbey Rodriguez M, J.; Roa-Rojas, J.

    2009-01-01

    We report experimental and theoretical study of crystallographic lattice and electronic structure of Sr 2 GdRuO 6 complex perovskite, which is used as precursor in the fabrication process of superconducting ruthenocuprate RuSr 2 GdCu 2 O 8 . Samples were produced by the standard solid state reaction. Rietveld refinement of experimental X-ray diffraction patterns shows that material crystallizes in a monoclinic structure, which belongs to the P2 1 /n (no.14) space group, with lattice parameters a=5.8019(6)A, b=5.8296(5)A, c=8.2223(7)A, and tilt angle β=90.258 deg. Calculations of electronic structure were performed by the density functional theory. The exchange and correlation potentials were included through the LDA+U approximation. Density of states (DOS) study was carried out considering the two spin polarizations. Results show Gd are majority responsible for the magnetic character in this material, but Ru contribution is also relevant because d-orbital is closer to Fermi level. Theoretical results evidence that Sr 2 GdRuO 6 material behaves as a magnetic semiconductor, with 20μ B effective magnetic moment.

  2. Double ferromagnetism in single-crystal Gd-Y-Lu alloys

    International Nuclear Information System (INIS)

    Ito, T.; Oka, M.; Legvold, S.; Beaudry, B.J.

    1984-01-01

    Magnetization, electrical resistivity, specific-heat and thermal-expansion measurements have been made on Gd-Y-Lu single crystals. Low isofield magnetization data for the a-axis sample of Gd 75 Y/sub 17.5/ Lu/sub 7.5/ exhibit two different Curie-Weiss regimes, which suggests double ferromagnetism. Electrical resistivity, specific-heat, and thermal-expansion data show two anomalies at the transition temperatures. The anomaly at 231.5 K shows a lambda-type second-order phase transition and the anomaly at 223 K shows a sharp spike first-order phase transition

  3. Efficient laser emission from cladding waveguide inscribed in Nd:GdVO(4) crystal by direct femtosecond laser writing.

    Science.gov (United States)

    Liu, Hongliang; Tan, Yang; Vázquez de Aldana, Javier R; Chen, Feng

    2014-08-01

    We report on the fabrication of depressed cladding waveguides in Nd:GdVO(4) laser crystal by using femtosecond laser inscription. The cross section of the structure is a circular shape with a diameter of 150 μm. Under the optical pump at 808 nm, the continuous wave (cw) as well as pulsed (Q-switched by graphene saturable absorber) waveguide lasing at 1064 nm has been realized, supporting guidance of both TE and TM polarizations. The maximum output power of 0.57 W was obtained in the cw regime, while the maximum pulse energy of the pulsed laser emissions was up to 19 nJ (corresponding to a maximum average output power of 0.33 W, at a resonant frequency of 18 MHz). The slope efficiencies achieved for the cw and pulsed Nd:GdVO(4) waveguide lasers were as high as 68% and 52%, respectively.

  4. Spectroscopic analysis and laser performance of Tm3+ : NaGd(MoO4)2 crystal

    International Nuclear Information System (INIS)

    Guo Weijie; Chen Yujin; Lin Yanfu; Gong Xinghong; Luo Zundu; Huang Yidong

    2008-01-01

    Detailed polarized spectral properties of Tm 3+ : NaGd(MoO 4 ) 2 crystal have been investigated. The room temperature absorption and fluorescence spectra were recorded. The fluorescence decay mechanisms of the 1 G 4 and 3 H 4 multiplets in Tm 3+ : NaGd(MoO 4 ) 2 crystal were discussed. Room temperature quasi-cw 1.9 μm laser emission from the Ti : sapphire laser pumped Tm 3+ : NaGd(MoO 4 ) 2 crystal has been demonstrated. The maximum output power of 170 mW has been achieved with a slope efficiency of 25%

  5. On improvement of scintillation characteristics of Gd2SiO5:Ce crystals by thermal treatment

    International Nuclear Information System (INIS)

    Bondar, Valery G.; Grinyov, Boris V.; Katrunov, Konstantin A.; Lisetski, Longin N.; Nagornaya, Lyudmila L.; Ryzhikov, Vladimir D.; Spasov, Vladimir G.; Starzhinskiy, Nikolai; Tamulaitis, Gintautas

    2005-01-01

    Effects of thermal treatment of Gd 2 SiO 5 :Ce crystals at T∼0.7T m under low pressure on their optical and scintillation properties were studied. It is shown that thermal treatment in the atmosphere with the chemical potential of ∼40 J mol -1 decreases the absorption in the UV region and substantially improves the crystal transparency in the region of intrinsic emission peaked at 427 nm.Narrowing of the emission band due to suppression of the long-wave component in the range of 520-560 nm, light output increase by 7-10%, decrease of the emission decay time, and improvement of thermal stability of the luminescence yield were also observed. Transformations of the ensemble of structural defects in cerium-activated gadolinium oxyorthosilicate crystals are under discussion

  6. Growth and optical properties of Tm:GdVO{sub 4} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Urata, Y.; Akagawa, K.; Wada, S.; Tashiro, H. [Photodynamics Research Center, Sendai (Japan). Inst. of Physical and Chemical Research; Suh, S.J.; Yoon, D.H. [Photodynamics Research Center, Sendai (Japan). Inst. of Physical and Chemical Research]|[Dept. of Metallurgical Engineering, Sung Kyun Kwan Univ. (Korea, Republic of); Fukuda, T. [Photodynamics Research Center, Sendai (Japan). Inst. of Physical and Chemical Research]|[Inst. for Materials Research, Tohoku Univ. (Japan)

    1999-04-01

    Thulium-doped gadolinium vanadate (Tm:GdVO{sub 4}) single crystal has been successfully grown by a modified Czochralski (CZ) technique. Effective distribution coefficient of Tm was determined to be 0.74. Absorption characterization was performed in the 800 nm region and the maximum absorption peak was found at 799 nm for {pi} polarization. Fluorescence spectra for tuning at the maximum absorption were obtained around 1.8-2.0 {mu}m region with 100 nm bandwidth. This suggests that a Tm:GdVO{sub 4} crystal is expected as a new promising LD pumped solid-state laser in the 2 {mu}m region. (orig.) 9 refs.

  7. A model for the magnetic domain structure of Gd at 77K

    International Nuclear Information System (INIS)

    Corner, W.D.; Saad, F.M.; Jones, D.W.; Jordan, R.G.

    1978-01-01

    Magnetic domain structures have been observed on planes perpendicular to the c and b axes of Gd crystals at 77K. Various types of domain boundary which might be found in an easy-cone ferromagnet are discussed. A model is presented which is consistent with observations. In this the easy-cone structure is maintained, but it is assumed that owing to the lower basal-plane anisotropy the magnetization component in the basal plane may change in direction within a single domain. (author)

  8. Thermal conductivity of ferrimagnet GdBaMn2O5.0 single crystals

    Directory of Open Access Journals (Sweden)

    J. C. Wu

    2017-05-01

    Full Text Available GdBaMn2O5.0 is a double-perovskite ferrimagnet consisting of pyramidal manganese layers. In this work, we study the in-plane and the c-axis thermal conductivities of GdBaMn2O5.0 single crystals at low temperatures down to 0.3 K and in high magnetic fields up to 14 T. The κc(T curve shows a broad hump below the Néel temperature (TN = 144 K, which indicates the magnon heat transport along the c axis. Whereas, the κa(T shows a kink at TN, caused by a magnon-phonon scattering effect. This anisotropic behavior is caused by the anisotropy of spin interactions along different directions. At very low temperatures, magnetic-field-induced changes of κa and κc, which is likely due to phonon scattering by free Gd3+ spins, is rather weak. This indicates that the spin coupling between Gd3+ and Mn2+/Mn3+ is rather strong at low temperatures.

  9. The RELixSn2 (RE=La–Nd, Sm, and Gd; 0≤x<1) series revisited. Synthesis, crystal chemistry, and magnetic susceptibilities

    International Nuclear Information System (INIS)

    Makongo, Julien P.A.; Suen, Nian-Tzu; Guo, Shengping; Saha, Shanta; Greene, Richard; Paglione, Johnpierre; Bobev, Svilen

    2014-01-01

    This study is concerned with the ternary compounds RELi x Sn 2 (RE=La–Nd, Sm, and Gd; 0≤x 2 phases. These materials crystallize with the base-centered orthorhombic space group Cmcm (No. 63), and can be formally assigned with the CeNiSi 2 structure type (Pearson symbol oC16). Our systematic single-crystal X-ray diffraction studies revealed substantial Li-deficiencies in all cases, with SmSn 2 (space group Cmmm, ZrGa 2 structure type, Pearson symbol oC12) and GdSn 2 (space group Cmcm, ZrSi 2 structure type, Pearson symbol oC12) being completely lithium-free. The structure refinements also uncovered positional disorder on the Sn site neighboring the vacancies. The Sn-disorder and the Li-deficiency correlate, and vary monotonically with the decreased size of the rare-earth atoms in the order RE=La–Nd. The SmSn 2 and GdSn 2 structures are devoid of any disorder. Temperature-dependent studies of the magnetic response of the title compounds are also presented and discussed. -- Graphical abstract: RELi x Sn 2 (RE=La–Nd, 0≤x 2 structure type (a). The Sn-disorder and the Li-deficiency correlate, and vary monotonically with the decreased size of the rare-earth atoms in the order RE=La–Nd. The SmSn 2 (b) and GdSn 2 (c) structures are devoid of any disorder. Highlights: • The crystal structures of the RELi x Sn 2 (RE=La–Nd, 0≤x 2 structure type or defect variant of the CeNiSi 2 structure type. • SmSn 2 is isotypic with the ZrGa 2 structure, while RESn 2 (RE=Gd–Lu) are isotypic with the ZrSi 2 structure

  10. Polarized spectroscopic properties of Er3+:Gd2SiO5 crystal and evaluation of Er3+:Yb3+:Gd2SiO5 crystal as a 1.55 μm laser medium

    International Nuclear Information System (INIS)

    Wang, H.; Huang, J.H.; Gong, X.H.; Chen, Y.J.; Lin, Y.F.; Luo, Z.D.; Huang, Y.D.

    2016-01-01

    An Er 3+ -doped Gd 2 SiO 5 single crystal with high optical quality has been grown by the Czochralski method. Polarized absorption and fluorescence spectra and fluorescence lifetime of the crystal were measured at room temperature. Intensity parameters, spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetimes were estimated on the basis of the Judd–Ofelt theory. Besides, potentiality of 1.55 μm laser emission in an Er 3+ –Yb 3+ co-doped Gd 2 SiO 5 crystal was evaluated.

  11. Structural, Magnetic and Microwave Properties of Nanocrystalline Ni-Co-Gd Ferrites

    Science.gov (United States)

    Nikzad, Alireza; Parvizi, Roghaieh; Rezaei, Ghasem; Vaseghi, Behrooz; Khordad, Reza

    2018-02-01

    A series of Co- and Gd-substituted NiFe2O4 ferrite nanoparticles with the formula Ni1- x Co x Fe2- y Gd y O4 (where x = 0.0-1.0 and y = 0.0-0.1) have been successfully synthesized using a hydrothermal method. X-ray diffraction and field emission scanning electron microscopy results indicated that a highly crystallized spherical ferrite nanoparticle structure was obtained along with an increase in the lattice parameters. Compositional analysis of the prepared nanoferrite powders has been carried out using energy-dispersive x-ray (EDX) spectra. The EDX analysis reveals the presence of Ni, Co, Gd and Fe elements in the specimens. Magnetization and the coercive field improved dramatically with an increase in the amount of cobalt and gadolinium added, attributed to the redistribution of cations in the spinel nanoferrite structure. Saturation magnetization and coercivity values up to 99 emu/g and 918 Oe, respectively, were measured using a vibration sample magnetometer at room temperature. Comparative microwave absorption experiments demonstrated that the reflection loss (RL) properties enhanced with increasing substitution of cations in the Ni-ferrite spinel structure for an absorber thickness of 1.8 mm. A maximum RL of - 26.7 dB was obtained for substituted Ni-Co-Gd nanoferrite with x = 1.0 and y = 0.1 at a frequency of 9.4 GHz with a bandwidth of 3.6 GHz (RL ≤ - 10 dB). Experimental results revealed that the synthesized nanoparticles possessed great potential in microwave absorption applications.

  12. Growth and laser characterization of mixed Nd:Lu xGd 1-xVO 4 laser crystals

    Science.gov (United States)

    Yu, Haohai; Yu, Yonggui; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang; Cheng, Xiufeng; Shao, Zongshu; Jiang, Minhua

    2006-08-01

    A new series Nd:Lu xGd 1-xVO 4 ( x=0.14, 0.32, 0.50, 0.61, 0.70 and 0.80) mixed laser crystals have been successfully grown by the Czochralski method. The X-ray powder diffraction (XRPD) analysis shows that the as-grown mixed crystals possess the ZrSiO 4 structure. The cell parameters are found to decrease with an increase of x. The optical absorption spectra of the mixed crystals have been measured at room temperature, and five strong-absorption bands centered at the wavelengths of 531, 594, 752, 807 and 880 nm have been revealed in all crystals. They are assigned to the different spin- and electric-dipole-allowed transition from the ground state to the 2K 13/2+ 4G 7/2+ 4G 9/2, 4G 5/2+ 2G 7/2, 4F 7/2+ 4S 3/2, 4F 5/2+ 2H 9/2 and 4F 3/2 energy levels, respectively. A continuous-wave (CW) laser output has been achieved with the mixed crystals at 1.06 μm under laser diode pumping. The maximum CW output power of 377.4 mW has been obtained with the pump power of 2 W, and the corresponding optical conversion efficiency is 18.8%.

  13. Hard X-ray MCD in GdNi/sub 5/ and TbNi/sub 5/ single crystals

    CERN Document Server

    Galera, R M

    1999-01-01

    XMCD experiments have been performed at the R L/sub 2,3/ and Ni K- edges on magnetically saturated single crystals of GdNi/sub 5/ and Tb Ni/sub 5/ ferromagnetic compounds. The spectra present huge and well structured dichroic $9 signals at both the R L/sub 2,3/ and the Ni K- edges. Structures from the quadrupolar (2p to 4f) transitions are clearly observed at the R L/sub 2,3/-edges. Though Ni is not magnetic, large intensities, up to 0.4, are measured at the $9 Ni K- edge. The Ni K-edge XMCD shows a three-peak structure which intensities dependent on the rare earth. (7 refs).

  14. EPR study of Gd sup 3 sup + centres in Tl sub 2 ZnF sub 4 crystals

    CERN Document Server

    Arakawa, M; Ebisu, H; Takeuchi, H

    2003-01-01

    EPR measurements have been made at room temperature on Tl sub 2 ZnF sub 4 crystals doped with Gd sup 3 sup + and co-doped with Gd sup 3 sup + and Li sup +. For crystals doped only with Gd sup 3 sup + , a spectrum with tetragonal symmetry (A centre) is observed. For co-doped crystals new spectra with tetragonal (B centre) and monoclinic (C centre) symmetries are observed in place of the spectrum of the A centre. The A centre is identified as the substitutional Gd sup 3 sup + ion at a Zn sup 2 sup + site in six-fold coordination without any local charge compensation in its immediate neighbourhood. On the basis of spin Hamiltonian separation analysis, the separated parameter b sub 2 sub a sub ( sub 1 sub ) for the C centre has a value close to the b sub 2 sup 0 parameter for the B centre. The B and C centres in co-doped crystals are ascribed to a Gd sup 3 sup + ion substituted for a Tl sup + site in nine-fold coordination, where the divalent excess positive charge on Gd sup 3 sup + is compensated by a Li sup + i...

  15. Structure of unliganded HSV gD reveals a mechanism for receptor-mediated activation of virus entry

    Energy Technology Data Exchange (ETDEWEB)

    Krummenacher, Claude; Supekar, Vinit M.; Whitbeck, J. Charles; Lazear, Eric; Connolly, Sarah A.; Eisenberg, Roselyn J.; Cohen, Gary H.; Wiley, Don C.; Carfi, Andrea (UPENN); (IRBM); (CHLMM)

    2010-07-19

    Herpes simplex virus (HSV) entry into cells requires binding of the envelope glycoprotein D (gD) to one of several cell surface receptors. The 50 C-terminal residues of the gD ectodomain are essential for virus entry, but not for receptor binding. We have determined the structure of an unliganded gD molecule that includes these C-terminal residues. The structure reveals that the C-terminus is anchored near the N-terminal region and masks receptor-binding sites. Locking the C-terminus in the position observed in the crystals by an intramolecular disulfide bond abolished receptor binding and virus entry, demonstrating that this region of gD moves upon receptor binding. Similarly, a point mutant that would destabilize the C-terminus structure was nonfunctional for entry, despite increased affinity for receptors. We propose that a controlled displacement of the gD C-terminus upon receptor binding is an essential feature of HSV entry, ensuring the timely activation of membrane fusion.

  16. Structural and magnetic properties of Gd-doped ZnO

    KAUST Repository

    Bantounas, Ioannis

    2014-01-01

    We use density functional theory to investigate structural and magnetic properties of Gd doped ZnO, accounting for the impurity 4f states using the GGA + U method. (i) We calculate the binding energy of forming [Gd-Gd] dimers, [VO - GdZn] and [VZn - GdZn] complexes and find that while the formation of [VZn - GdZn] is favourable, [GdZn - GdZn] and [VO - GdZn] complexes are less likely to form. Next, (ii) we investigate the spacial arrangement of two (and three) GdZn impurities in a 3 × 3 × 2 supercell and find that the magnetic impurities are energetically favourable when occupying distant lattice sites. Finally, we study the nature of interactions between the magnetic impurities (iii) for Gd in nearest-neighbour and non-nearest-neighbour Zn sites, (iv) in the presence of Zn or O vacancies, and (v) with and without additional charge carriers. Our results show mainly paramagnetic behaviour. In a few cases, e.g. magnetic impurities occupying in-plane nearest-neighbour zinc sites with n-type carrier doping, weak ferromagnetic coupling is observed. This magnetic ordering is of the order of a few meV and can be easily destroyed by thermal fluctuations. We thus expect Gd:ZnO to show paramagnetic behaviour at temperatures approaching room temperature.

  17. Luminescence and light yield of (Gd2Y)(Ga3Al2)O12:Pr3+ single crystal scintillators

    Science.gov (United States)

    Lertloypanyachai, Prapon; Pathumrangsan, Nichakorn; Sreebunpeng, Krittiya; Pattanaboonmee, Nakarin; Chewpraditkul, Weerapong; Yoshikawa, Akira; Kamada, Kei; Nikl, Martin

    2017-06-01

    Praseodymium-doped (Gd2Y)(Ga3Al2)O12 (GYGAG: Pr) single crystals are grown by the micro-pulling down method with different Pr concentrations. The energy transfer process between Pr3+ and Gd3+ is investigated by photoluminescence excitation (PLE) and emission (PL) spectra measurements. Photoelectron yield measurements are carried out using photomultiplier. At 662 keV γ-rays, photoelectron yield of 2520 phe/MeV obtained for the GYGAG: Pr (0.01%) sample is larger than that of 1810 phe/MeV obtained for BGO crystal. Light yield degradation for the GYGAG: Pr scintillators is presumably due to the energy transfer from 5d state of Pr3+ to 4f state of Gd3+ together with the concentration quenching in the Gd3+-sublattice.

  18. Effect of Gd substitution on structure and spectroscopic properties of (Lu,Gd)2O3:Eu ceramic scintillator

    Science.gov (United States)

    Cao, Maoqing; Hu, Zewang; Ivanov, Maxim; Dai, Jiawei; Li, Chaoyu; Kou, Huamin; Shi, Yun; Chen, Haohong; Xu, Jiayue; Pan, Yubai; Li, Jiang

    2018-02-01

    In this paper, (Lu1-xGdx)2O3:Eu (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) ceramics were consolidated by the solid-state reaction method combined with vacuum sintering without sintering aids. We investigated the effect of the varying contents of Gd2O3 on the structure and spectroscopic properties of (Lu1-xGdx)2O3:Eu ceramics. X-ray diffraction (XRD) patterns indicate that proper amount of Gd2O3 can incorporate well with Lu2O3 and form Lu2O3-Gd2O3 solid solution. However, excessive Gd3+-doping in Lu2O3 will lead to the cubic phase transforming into monoclinic even hexagonal phase. The Gd3+ substitution no more than 50% of Lu2O3 enhances the radioluminescence, and reduces the fluorescence lifetime. Transmittance, photoluminescence, and radiation damage of the (Lu1-xGdx)2O3:Eu scintillation ceramics were also studied.

  19. In pursuit of the rhabdophane crystal structure: from the hydrated monoclinic LnPO{sub 4}.0.667H{sub 2}O to the hexagonal LnPO{sub 4} (Ln = Nd, Sm, Gd, Eu and Dy)

    Energy Technology Data Exchange (ETDEWEB)

    Mesbah, Adel, E-mail: adel.mesbah@cea.fr [ICSM, UMR 5257 CNRS – CEA – ENSCM – Université de Montpellier, Site de Marcoule - Bât 426, BP 17171, 30207 Bagnols/Cèze (France); Clavier, Nicolas [ICSM, UMR 5257 CNRS – CEA – ENSCM – Université de Montpellier, Site de Marcoule - Bât 426, BP 17171, 30207 Bagnols/Cèze (France); Elkaim, Erik [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Szenknect, Stéphanie; Dacheux, Nicolas [ICSM, UMR 5257 CNRS – CEA – ENSCM – Université de Montpellier, Site de Marcoule - Bât 426, BP 17171, 30207 Bagnols/Cèze (France)

    2017-05-15

    The dehydration process of the hydrated rhabdophane LnPO{sub 4}.0.667H{sub 2}O (Ln = La to Dy) was thoroughly studied over the combination of in situ high resolution synchrotron powder diffraction and TGA experiments. In the case of SmPO{sub 4}.0.667H{sub 2}O (monoclinic, C2), a first dehydration step was identified around 80 °C leading to the formation of SmPO{sub 4}.0.5H{sub 2}O (Monoclinic, C2) with Z =12 and a =17.6264(1) Å, b =6.9704(1) Å, c =12.1141(1) Å, β=133.74(1) °, V =1075.33(1) Å{sup 3}. In agreement with the TGA and dilatometry experiments, all the water molecules were evacuated above 220 °C yielding to the anhydrous form, which crystallizes in the hexagonal P3{sub 1}21 space group with a =7.0389(1) Å, c =6.3702(1) Å and V =273.34(1) Å{sup 3}. This study was extended to selected LnPO{sub 4}.0.667H{sub 2}O samples (Ln= Nd, Gd, Eu, Dy) and the obtained results confirmed the existence of two dehydration steps before the stabilization of the anhydrous form, with the transitory formation of LnPO{sub 4}.0.5H{sub 2}O. - Graphical abstract: The dehydration process of the rhabdophane SmPO{sub 4}.0.667H{sub 2}O was studied over combination of in situ high resolution synchrotron powder diffraction and TGA techniques, a first dehydration was identified around 80 °C leading to the formation of SmPO{sub 4}.0.5H{sub 2}O (Monoclinic, C2). Then above 220 °C, the anhydrous form of the rhabdophane SmPO{sub 4} was stabilized and crystallizes in the hexagonal P3{sub 1}21 space group. - Highlights: • In situ synchrotron powder diffraction was carried out during the dehydration of the rhabdopahe LnPO{sub 4}.0.667H{sub 2}O. • The heat of the rhabdophane LnPO{sub 4}.0.667H{sub 2}O leads to LnPO{sub 4}.0.5H{sub 2}O then to anhydrous rhabdophane LnPO{sub 4}. • LnPO{sub 4}.0.5H{sub 2}O (monoclinic, C2) and LnPO{sub 4} (Hexagonal, P3{sub 1}21) were solved over the use of direct methods.

  20. Characterization of mixed Nd :LuxGd1-xVO4 laser crystals

    Science.gov (United States)

    Yu, H. H.; Zhang, H. J.; Wang, Z. P.; Wang, J. Y.; Yu, Y. G.; Cheng, X. F.; Shao, Z. S.; Jiang, M. H.; Ling, Z. C.; Xia, H. R.

    2007-06-01

    A series of laser crystals Nd :LuxGd1-xVO4 (x=0.14,0.32,0.50,0.61,0.70,0.80) was grown by the Czochralski method. The thermal properties, including the average linear thermal expansion coefficients, thermal diffusion coefficients, specific heats, and thermal conductivities, of the mixed crystals were obtained. The material constants Ms for the thermal stress resistance figure were calculated and showed that the thermal fracture limits of the mixed crystals should be comparable with that of Nd :YVO4. The polarization absorption spectra from 240to1000nm were measured at room temperature and the absorption cross sections at 809nm were calculated. Using the Judd-Ofelt theory, the theoretical radiative lifetimes were calculated and compared with the experimental results. Continuous wave laser performances were achieved with the mixed crystals at the wavelength of 1.06μm when they were pumped by a laser diode. Thermal, optical, and laser properties have shown variation as a function of x and proved that the mixed crystals are good laser materials.

  1. The magnetic structure of GdNi2B2C investigated by neutron powder diffraction

    International Nuclear Information System (INIS)

    Barcza, A.; Rotter, M.; Doerr, M.; Beuneu, B.

    2005-01-01

    Full text: The group of ReT 2 B 2 C (Re=rare earth, T=transition metal) shows a very interesting interplay between magnetism and superconductivity due to the rare earth metals. In this work the magnetism of GdNi 2 B 2 C was studied with neutron diffraction. Previous investigations with x-ray diffraction methods have determined the crystal structure as a body centered tetragonal structure (I 4/mmm). Hot neutrons were used for the diffraction experiment, because the absorption cross section of Gd is significantly smaller for short wavelengths. The investigated compound orders magnetically at TN=19.5 K, and so the experiment was carried out at two temperatures, namely 30 K and 2.2 K. The results show a incommensurate spin structure with a propagation vector of (0.55 0 0). To confirm this results additional simulations of the spin structure were done based on the Standard Model of rare earth magnetism. A neutron diffraction pattern was calculated using the McPhase program package and is compared to the experimental data. (author)

  2. Structural and magnetic properties of Gd/Fe multilayers grown by pulsed laser deposition

    DEFF Research Database (Denmark)

    Kant, K. Mohan; Bahl, Christian Robert Haffenden; Pryds, Nini

    2010-01-01

    This work investigates the structural and the magnetic properties of Gd/Fe multilayered thin films grown by pulsed laser deposition onto Si (001) substrates at room temperature. he Fe layer thickness is varied from 70 to 150 nm and its effect on the structural and magnetic properties of Fe/Gd/Fe ...

  3. Structure evolution and magnetic properties of annealed nanoscale Gd/Ti multilayers

    Directory of Open Access Journals (Sweden)

    Larrañaga A.

    2013-01-01

    Full Text Available The structure and magnetic properties were comparatively analyzed for [Gd/Ti]n multilayers with Gd layer thickness of 1.5 to 12 nm. Multilayers were deposited by sputtering technique at room temperature and annealed for the temperatures up to 400 ºC. It was observed that the samples are highly textured in a different way depending on the Gd layer thickness and annealing temperature. It was found that the heat treatment practically does not change the Gd grain size. The lattice parameters obtained from X-ray results change significantly only for [Gd(1.5nm/Ti]50 multilayers, but their values remain higher than for the bulk Gd. The initial slope of the temperature dependence of magnetization near Curie temperature becomes steeper and Curie temperature increases upon annealing. Curie temperature variation can be understood by taking into account both relaxation of the lattice imperfections and change in lattice constants.

  4. Growth and properties of Nd:(Lu xGd 1-x) 3Ga 5O 12 laser crystal by Czochralski method

    Science.gov (United States)

    Jia, Zhitai; Tao, Xutang; Yu, Haohai; Dong, Chunming; Zhang, Jian; Zhang, Huaijin; Wang, Zhengping; Jiang, Minhua

    2008-10-01

    In this paper we report the growth and characterization of Nd:(Lu xGd 1-x) 3Ga 5O 12 crystal for the first time. The polycrystalline materials were synthesized by conventional solid-state reaction. Single crystal with good optical quality was successfully obtained and the dimensions of the as-grown crystal were Ø21 × 30 mm 3. X-ray powder diffraction studies confirm that the Nd:(Lu xGd 1-x) 3Ga 5O 12 crystal is isostructural with Gd 3Ga 5O 12 with unit cell parameter of 1.2361 nm which is less than that of Gd 3Ga 5O 12 crystal (1.2376 nm). The absorption and emission spectra of the crystal at room temperature have also been studied. Continuous-wave (CW) laser performance at 1.06 μm has been demonstrated on the crystal.

  5. Optical properties and radiation response of Ce{sup 3+}-doped GdScO{sub 3} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yamaji, Akihiro; Fujimoto, Yutaka; Futami, Yoshisuke; Yokota, Yuui; Kurosawa, Shunsuke [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Kochurikhin, Vladimir [General Physics Institute, 38 Vavilov Str., 119991 Moscow (Russian Federation); Yanagida, Takayuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Yoshikawa, Akira [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

    2012-12-15

    10%-Ce doped GdScO{sub 3} perovskite type single crystal was grown by the Czochralski process. The Ce concentration in the crystal was measured. No impurity phases were observed by powder X-ray diffraction analysis. We evaluated the optical and radiation properties of the grown crystal. Ce:GdScO{sub 3} crystal showed photo- and radio-luminescence peaks due to Ce{sup 3+} of 5d-4f transition and colour centre. The photoluminescence decay time was sub-ns order. The relative light yield under 5.5 MeV alpha-ray excitation was calculated to be approximately 9% of BGO. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. A Dual-Crystal Cavity Ho,Tm:GdVO4 Laser

    International Nuclear Information System (INIS)

    Zhu Guo-Li; Ju You-Lun; Yao Bao-Quan; Wang Yue-Zhu

    2012-01-01

    We report a 31.2 W cw diode-pumped cryogenic Ho(0.4at.%),Tm(4at.%):GdVO 4 laser in a dual-crystal cavity. The pumping sources are two fiber-coupled laser diodes with a fiber core diameter of 0.4 mm, both of which can supply 42 W near 802 nm. With an incident pump power of 70.3 W at 802.4 nm, a cw output power of 31.2 W at 2.05 μm is attained, corresponding to an optical-to-optical conversion efficiency of 44.4%. The M 2 factor is measured as ∼1.3 under an output power of 20 W. (fundamental areas of phenomenology(including applications))

  7. Optical waveguides in Nd:GdVO4 crystals fabricated by swift N3+ ion irradiation

    Science.gov (United States)

    Dong, Ningning; Yao, Yicun; Chen, Feng

    2012-12-01

    Optical planar waveguides have been manufactured in Nd:GdVO4 crystal by swift N3+ ions irradiation at fluence of 1.5 × 1014 ions/cm2. A typical "barrier"-style refractive index profile was formed and the light can be well confined in the waveguide region. The modal distribution of the guided modes obtained from numerical calculation has a good agreement with the experimental modal distribution. The measured photoluminescence spectra revealed that the fluorescence properties of the Nd3+ ions have been modified to some extent in the waveguide's volume. The propagation loss of the planar waveguide can decrease to lower than 1 dB/cm after adequate annealing.

  8. Structural investigation on K3Gd5(PO4)6 in between 20 K to 1073 K

    International Nuclear Information System (INIS)

    Bevara, Samatha; Achary, S.N.; Tyagi, A.K.; Mishra, K.K.; Ravindran, T.R.; Sinha, A.K.; Sastry, P.U.

    2016-01-01

    Evolution of crystal structure of K 3 Gd 5 (PO 4 ) 6 in the temperature range from 20 K to 1073 K, as observed from combined variable temperature X-ray diffraction (using both synchrotron source and Cu K α lab source) and Raman spectroscopic studies is communicated in the manuscript. The title compound has an open tunnel containing three dimensional structure built by periodic arrangements of (Gd 5 (PO 4 ) 6 ) 3- ions which in turn are formed by PO 4 tetrahedra and GdO n (n = 8 and 9) polyhedra and these tunnels are occupied by K + ions. The XRD patterns in the entire temperature range of study indicated no change in the crystal structural, which is also supported by differential thermal analyses and Raman spectroscopy. Average axial thermal expansion coefficients between 20K and 1073 K are : α a =10.6 x 10 -6 K -1 , α b = 5.5 x 10 -6 K -1 and α c = 16.4 X 10.6 -6 K -1 . (author)

  9. Room-temperature picosecond high-order stimulated Raman scattering in laser garnet crystal hosts Gd3Ga5O12, Gd3Sc2Ga3O12, and Ca3(Nb,Ga)2Ga3O12

    International Nuclear Information System (INIS)

    Kaminskii, Alexandr A; Eichler, H J; Findeisen, J; Ueda, Ken-ichi; Fernandez, J; Balda, R

    1998-01-01

    High-order Stokes and anti-Stokes generation in the visible and near-infrared in cubic laser crystal hosts Gd 3 Ga 5 O 12 , Gd 3 Sc 2 Ga 3 O 12 , and Ca 3 (Nb,Ga) 2 Ga 3 O 12 was observed for the first time. All scattering-laser components were identified and attributed to the SRS-active vibration modes of these garnet crystals. (letters to the editor)

  10. Structural characterization of the CeO{sub 2}/Gd{sub 2}O{sub 3} mixed system by synchrotron X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Artini, Cristina, E-mail: c.artini@ge.ieni.cnr.it [Dipartimento di Chimica e Chimica Industriale, Universita degli Studi di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Costa, Giorgio A., E-mail: costa@chimica.unige.it [Dipartimento di Chimica e Chimica Industriale, Universita degli Studi di Genova, Via Dodecaneso 31, 16146 Genova (Italy); CNR-SPIN Genova, Corso Perrone 24, 16152 Genova (Italy); Pani, Marcella, E-mail: marcella@chimica.unige.it [Dipartimento di Chimica e Chimica Industriale, Universita degli Studi di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Lausi, Andrea, E-mail: andrea.lausi@elettra.trieste.it [Sincrotrone Trieste S.C.p.A., ss 14, km 163, 5, 34149 Basovizza, Trieste (Italy); Plaisier, Jasper, E-mail: jasper.plaisier@elettra.trieste.it [Sincrotrone Trieste S.C.p.A., ss 14, km 163, 5, 34149 Basovizza, Trieste (Italy)

    2012-06-15

    The structural determination of the CeO{sub 2}/Gd{sub 2}O{sub 3} mixed system is a non-trivial problem because of the close resemblance between the ionic sizes of Ce{sup 4+} and Gd{sup 3+} and between the crystal structures of CeO{sub 2} and Gd{sub 2}O{sub 3}. (Ce{sub 1-x}Gd{sub x})O{sub 2-x/2} powder samples with x ranging between 0 and 1 have been synthesized by coprecipitation of mixed oxalates and subsequent thermal decomposition in air at 1200 Degree-Sign C followed by slow cooling. Synchrotron powder X-ray diffraction data were collected and refined by the Rietveld method. Lattice parameters do not follow Vegard's law and no peak splitting has been observed for any composition, meaning that no biphasic regions exist over the whole compositional range. The same hybrid structural model - a proper mixture of the structures of the two pure oxides - was used for the refinements, allowing to account for the data observed. - graphical abstract: Substituting Ce{sup 4+} by Gd{sup 3+}, a gradual transition from the F structure (typical of CeO{sub 2}) to the C structure (typical of Gd{sub 2}O{sub 3}) takes place. The lattice parameters do not follow Vegard's law. Highlights: Black-Right-Pointing-Pointer A structural study of Ce-Gd mixed oxides has been performed. Black-Right-Pointing-Pointer In (Ce{sub 1-x}Gd{sub x})O{sub 2-x/2} a solid solution forms for 0{<=}x{<=}0.3. Black-Right-Pointing-Pointer For x>0.3 a gradual transition from the C to the F structure is observed. Black-Right-Pointing-Pointer Lattice parameters do not follow Vegard's law.

  11. Magnesium substitutions in rare-earth metal germanides with the Gd5Si4 type. Synthesis, structure determination and magnetic properties of RE5-xMgxGe4 (RE=Gd-Tm, Lu and Y)

    Energy Technology Data Exchange (ETDEWEB)

    Sarrao, J L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Tobash, P H [UNIV. OF DE; Bobev, S [UNIV. OF DE

    2009-01-01

    A series of magnesium-substituted rare-earth metal germanides with a general formula RE{sub 5-x}Mg{sub x}Ge{sub 4} (x {approx} 1.0-2.3; RE =Gd-Tm, Lu, Y) have been synthesized by high-temperature reactions and structurally characterized by single-crystal X-ray diffraction. These compounds crystallize with the common Gd{sub 5}Si{sub 4} type in the orthorhombic space group Pnma (No. 62; Z =4; Pearson's code oP36) and do not appear to undergo temperature-induced crystallographic phase transitions down to 120 K. Replacing rare-earth metal atoms with Mg, up to nearly 45 % at., reduces the valence electron count and is clearly expressed in the subtle changes of the Ge-Ge and metal-metal bonding. Magnetization measurements as a function of the temperature and the applied field reveal complex magnetic structures at cryogenic temperatures, and Curie-Weiss paramagnetic behavior at higher temperatures. The observed local moment magnetism is consistent with RE+ ground states in all cases. In the magnetically ordered phases, the magnetization cannot reach saturation in fields up to 50 kOe. The structural trends across the series and the variations of hte magnetic properties as a function of the Mg content are also discussed. KEYWORDS: Rare-earth intermetallics, germanides, crystal structure,Gd{sub 5}Si{sub 4} type.

  12. Valence and magnetic state of transition-metal and rare-earth ions in single-crystal multiferroics RMn{sub 2}O{sub 5} (R = Y, Bi, Eu, Gd) from X-ray photoelectron spectroscopy data

    Energy Technology Data Exchange (ETDEWEB)

    Kozakov, A.T. [Scientific-Research Institute of Physics at Southern Federal University, 194 Stachki, Rostov-na-Donu 344194 (Russian Federation); Kochur, A.G., E-mail: agk@rgups.ru [Rostov State University of Transport Communication, 2 Narodnogo Opolcheniya, Rostov-na-Donu 344038 (Russian Federation); Nikolsky, A.V.; Googlev, K.A.; Smotrakov, V.G.; Eremkin, V.V. [Scientific-Research Institute of Physics at Southern Federal University, 194 Stachki, Rostov-na-Donu 344194 (Russian Federation)

    2011-11-15

    Highlights: {yields} Single crystals RMn{sub 2}O{sub 5} (R = Y, Bi, Eu, Gd) and YMnO{sub 3} are grown. {yields} Core level XPS are measured and calculated with inclusion of temperature effect. {yields} Mn2p, Mn3s, R4s, and R4d (R = Eu, Gd) XPS are sensitive to valence and spin state. {yields} Paramagnetic moments per structural cell are estimated. - Abstract: Single crystals of orthorhombic multiferroics RMn{sub 2}O{sub 5} (R = Y, Bi, Eu, Gd), and of hexagonal manganite YMnO{sub 3} are grown. X-ray photoelectron spectra of the core levels of the Mn, Y, Bi, Eu, Gd, and O atoms in multiferroics are obtained at room temperature with the ESCALAB 250 microprobe system with monochromatization of the exciting X-ray radiation. X-ray photoelectron spectra of Mn2p, Mn3s, R4s, and R4d (R = Eu, Gd) levels are assigned based on one-configuration isolated-ion approximation calculations with taking the temperature effect into account. It is shown using the photoelectron spectroscopy methods that both Mn{sup 3+} and Mn{sup 4+} ions are present in orthorhombic multiferroics, while Eu and Gd are in trivalent state. Paramagnetic moments per structural unit are calculated and compared with those determined from our spectroscopic data and with the data from other authors.

  13. Crystal structure, magnetization, {sup 125}Te NMR, and Seebeck coefficient of Ge{sub 49}Te{sub 50}R{sub 1} (R = La, Pr, Gd, Dy, and Yb)

    Energy Technology Data Exchange (ETDEWEB)

    Levin, E.M., E-mail: levin@iastate.edu [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Cooling, C. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Bud’ko, S.L. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Straszheim, W.E. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Lograsso, T.A. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Department of Materials Sciences and Engineering, Iowa State University, Ames, IA 50011 (United States)

    2017-05-01

    GeTe, a self-doping semiconductor, is a well-known base compound for thermoelectric and phase-change materials. It is known, that replacement of Ge in Ag{sub 6.5}Sb{sub 6.5}Ge{sub 37}Te{sub 50} (TAGS-85) material by rare earth Dy significantly enhances both the power factor and thermoelectric figure of merit. Here we demonstrate how replacement of Ge in GeTe by rare earths with different atomic size and localized magnetic moments affect XRD patterns, magnetization, {sup 125}Te NMR spectra and spin-lattice relaxation, and the Seebeck coefficient of the alloys with a nominal composition of Ge{sub 49}Te{sub 50}R{sub 1} (R = La, Pr, Gd, Dy, and Yb). SEM, EDS and WDS data show that rare earth atoms in the matrix are present at smaller extent compared to a nominal composition, whereas rare earth also is present in inclusions. Rare earths affect the Seebeck coefficient, which is a result of interplay between the reduction due to higher carrier concentration and enhancement due to magnetic contribution. The effect of replacement of Ge in GeTe by Dy on the Seebeck coefficient is smaller than that observed in Ag{sub 6.5}Sb{sub 6.5}Ge{sub 36} Te{sub 50}Dy{sub 1}. This can be explained by larger amount of rare earth, which can be embedded into the lattice of materials containing [Ag + Sb] atomic pairs and possible effect from these pairs. - Highlights: • The effects of rare earth in Ge{sub 49}Te{sub 50}R{sub 1} (R = La, Pr, Gd, Dy, and Yb) are studied. • Rare earth atoms in the matrix are present at smaller extent compared to a nominal composition. • The effect on the Seebeck coefficient is a result from carrier concentration and magnetic contribution.

  14. Inhomogeneous ferrimagnetic-like behavior in Gd2/3Ca1/3MnO3 single crystals

    International Nuclear Information System (INIS)

    Haberkorn, N.; Larregola, S.; Franco, D.; Nieva, G.

    2009-01-01

    We present a study of the magnetic properties of Gd 2/3 Ca 1/3 MnO 3 single crystals at low temperatures, showing that this material behaves as an inhomogeneous ferrimagnet. In addition to small saturation magnetization at 5 K, we have found history dependent effects in the magnetization and the presence of exchange bias. These features are compatible with microscopic phase separation in the clean Gd 2/3 Ca 1/3 MnO 3 system studied

  15. Ising-like spin anisotropy and competing antiferromagnetic-ferromagnetic orders in GdBaCo2O5.5 single crystals.

    Science.gov (United States)

    Taskin, A A; Lavrov, A N; Ando, Yoichi

    2003-06-06

    In RBaCo2O5+x compounds (R is rare earth), a ferromagnetic-antiferromagnetic competition is accompanied by a giant magnetoresistance. We study the magnetization of detwinned GdBaCo2O5.5 single crystals and find a remarkable uniaxial anisotropy of Co3+ spins which is tightly linked with the chain oxygen ordering in GdO0.5 planes. Reflecting the underlying oxygen order, CoO2 planes also develop a spin-state order consisting of Co3+ ions in alternating rows of S=1 and S=0 states. The magnetic structure appears to be composed of weakly coupled ferromagnetic ladders with Ising-like moments, which gives a simple picture for magnetotransport phenomena.

  16. Optical waveguide formed in Yb:GdCOB and Yb:YCOB crystals by 3.0MeV O{sup +} implantation

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Yang, E-mail: sdujy@163.com [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China)

    2013-07-15

    Planar optical waveguides were formed in Yb:GdCOB and Yb:YCOB crystals by 3.0 MeV O{sup +} ion implantation at fluence of 2 × 10{sup 15} ions/cm{sup 2} at room temperature, respectively. The prism coupling method was performed to characterize the dark-mode property of the waveguides. The refractive index profiles in the waveguides were reconstructed by reflectivity calculation method (RCM). The results show that after the implantation, a 1.5 μm-wide region with enhanced refractive-index was formed beneath the sample surfaces to act as waveguide structures for both Yb:GdCOB and Yb:YCOB.

  17. SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURES ...

    African Journals Online (AJOL)

    B. S. Chandravanshi

    ABSTRACT. Reaction of [VO(acac)2] (acac = acetylacetonate) with ... Single crystal X-ray structural studies indicate that the hydrazone ligands coordinate to ..... Molecular structure of complex (1) at 30% probability displacement. Figure 4.

  18. SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURE ...

    African Journals Online (AJOL)

    Preferred Customer

    Reaction of [MoO2(acac)2] (where acac = acetylacetonate) with N'-(2-hydroxy-4- ... Single crystal X-ray structural studies indicate that the hydrazone ligand coordinates .... Molecular structure of the complex at 30% probability displacement.

  19. Phase transition control, melt growth of (Gd,RE)F{sub 3} single crystal and their luminescent properties

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, Akira, E-mail: yosikawa@tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Jouini, Anis [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); BerlinSolar GmbH, Magnusstrasse 11, D-12489 Berlin (Germany); Kamada, Kei [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Boulon, Georges [Physical Chemistry of Luminescent Materials, Claude Bernard/Lyon 1 University, UMR 5620 CNRS, Villeurbanne (France); Nikl, Martin [Institute of Physics AS CR, Cukrovarnicka 10, Prague 16253 (Czech Republic); Saito, Fumio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2009-12-15

    Rare-earth sesquifluorides with no absorption in visible spectral region, such as LaF{sub 3}, GdF{sub 3}, LuF{sub 3}, YF{sub 3}, ScF{sub 3}, are the topic of intense study as a host for luminescence materials. However, except Nd:LaF{sub 3}, they are not studied as a host for laser materials. The main obstacle troubling further study of GdF{sub 3}, LuF{sub 3}, YF{sub 3}, ScF{sub 3} single crystal is the fact that there is first-order phase transition (LaF{sub 3} type{leftrightarrow}{beta}-YF{sub 3} type for GdF{sub 3}, {alpha}-YF{sub 3} type{leftrightarrow}{beta}-YF{sub 3} type for the rest) between the room and melting temperature.To prevent the phase transition, first of all, we have tried to make solid solution between GdF{sub 3} and YF{sub 3} in such a way that the average cation radii can be shifted to the size that does not have phase transition. Ce{sup 3+} perturbed luminescence was observed in the Ce- and Sr-codoped GdF{sub 3}-YF{sub 3} system. Similar solid solution concept was applied to the combination between GdF{sub 3} and YbF{sub 3}. The emission spectrum of Yb{sup 3+} that exhibits broad bands around 1 {mu}m was observed. Room temperature up-conversion luminescence spectra of Pr{sup 3+}-doped Gd{sub 1-x}Yb{sub x}F{sub 3} were studied and visible emission from Pr{sup 3+} was obtained under infrared laser pumping in the Yb{sup 3+} broad absorption band at 935.5 nm.

  20. Crystal phase transition in LixNa1-xGdF4 solid solution nanocrystals - Tuning of optical properties

    KAUST Repository

    Bański, Mateusz

    2014-01-01

    The influence of precursor composition on the crystallization of LixNa1-xGdF4 is investigated and discussed. Nanocrystals are prepared from the thermal decomposition of trifluoroacetates in the presence of trioctylphosphine oxide to provide control over particle size. A crystal phase transition from hexagonal to cubic and to tetragonal is observed by increasing lithium trifluoroacetate (Li-TFA) in the solution. Controlling the composition of LixNa1-xGdF4 nanocrystals results in modified crystal field symmetry and emission properties from doped europium (Eu3+) ions. We report that for lithium (Li+) substitution <15%, the hexagonal crystal field is preferred, while the Eu3+ emission is already tuned, whereas at higher Li+ substitution, a phase change takes place and the number of crystalline matrix defects increases which is reflected in the optical properties of Eu3+. From Eu3+ emission properties, the optimum Li+ content is determined to be ∼6.2% in the prepared LixNa1-xGdF4 nanocrystals.

  1. Crystal structure determination of Efavirenz

    International Nuclear Information System (INIS)

    Popeneciu, Horea; Dumitru, Ristoiu; Tripon, Carmen; Borodi, Gheorghe; Pop, Mihaela Maria

    2015-01-01

    Needle-shaped single crystals of the title compound, C 14 H 9 ClF 3 NO 2 , were obtained from a co-crystallization experiment of Efavirenz with maleic acid in a (1:1) ratio, using methanol as solvent. Crystal structure determination at room temperature revealed a significant anisotropy of the lattice expansion compared to the previously reported low-temperature structure. In both low- and room temperature structures the cyclopropylethynyl fragment in one of the asymmetric unit molecules is disordered. While at low-temperature only one C atom exhibits positional disorder, at room temperature the disorder is present for two C atoms of the cyclopropane ring

  2. Pressure-enhanced light emission and its structural origin in Er:GdVO 4

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Fang; Yue, Binbin; Cheng, Zhenxiang; Shen, Hui; Yang, Ke; Hong, Xinguo; Chen, Bin; Mao, Ho-Kwang

    2017-01-09

    Rare earth phosphors have been widely studied because of their sharp emission lines and excellent optical performance. However, photoluminescence (PL) tuning by crystal field in Er3+ embedded phosphors has always been a challenge. Here, we demonstrate that pressure can help to enhance the red and green light emission simultaneously in Er:GdVO4. Synchrotron X-ray diffraction investigations revealed that a structural phase transition was responsible for the enhancement. Our work brightens the future prospects for applications of Er3+-based PL materials in various fields, such as high power lasers and (bio) medical imaging.

  3. SYNTHESIS, CHARACTERIZATION, AND CRYSTAL STRUCTURE ...

    African Journals Online (AJOL)

    a

    KEY WORDS: Barium, Crystal structure, 2,6-Pyridinedicarboxylic acid .... The rational design of novel metal-organic frameworks has attracted great ..... Bond, A.D.; Jones, W. Supramolecular Organization and Materials Design, Jones, W.; Rao,.

  4. Growth and scintillation properties of Ce{sup 3+}-doped (Y{sub 1-x}Gd{sub x})AlO{sub 3} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, Yutaka; Wakahara, Shingo; Suzuki, Shotaro; Kurosawa, Shunsuke [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Yoshikawa, Akira [Institute of Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

    2012-12-15

    The optical and scintillation properties of 0.5% fixed Ce-doped (Y{sub 1-x}Gd{sub x})AlO{sub 3} single crystals have been investigated at three different levels of Gd doping: x = 0.2, 0.4 and 0.6. Single crystal of the Ce{sup 3+}-doped (Y{sub 0.8}Gd{sub 0.2})AlO{sub 3}, (Y{sub 0.6}Gd{sub 0.4})AlO{sub 3} and (Y{sub 0.4}Gd{sub 0.6})AlO{sub 3} were successfully grown by {mu}-PD technique in nitrogen atmosphere. From X-ray diffraction analysis, no impurity phase was detected for the grown Ce-doped crystals. Ce-doped (Y{sub 0.6}Gd{sub 0.4})AlO{sub 3} crystal demonstrated highest fluorescence quantum efficiency ({proportional_to} 25%) with improvement of excitation efficiency due to the Gd-doping. When irradiated by the alpha-rays from a {sup 241}Am source, all the Ce-doped crystals showed luminescence band that corresponding to 5d (t{sub 2g})-4f transition of Ce{sup 3+}. The scintillation decay time was characterized by two components; the fast component (5-15 ns) is ascribed to 5d-4f transition of Ce{sup 3+}, while the slow one (100-200 ns) may be related to energy transfer between Ce{sup 3+} and Gd{sup 3+} ion. According to the result of {sup 137}Cs gamma-ray irradiated pulse height spectra compared with BGO scintillator, the relative scintillation light output was found to be about 12200 {+-} 1220 (Gd 20%) and 16000 {+-} 1600 (Gd 40%) ph/MeV. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Optical and magneto-optical properties of single crystals of RFe{sub 2} (R = Gd, Tb, Ho, and Lu) and GdCo{sub 2} intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.J.

    1999-02-12

    The author has studied the diagonal and off-diagonal optical conductivity of RFe{sub 2}(R = Gd, Tb, Ho, Lu) and GdCo{sub 2} single crystals grown by the flux method. Using spectroscopic ellipsometry the author has measured the dielectric function from 1.5 to 5.5 eV. The magneto-optical Kerr spectrometer at temperatures between 7 and 295 K and applied magnetic fields between 0.5 to 1.6 T. The apparatus and calibration method are described in detail. Using magneto-optical data and optical constants he derives the experimental value of the off-diagonal conductivity components. Theoretical calculations of optical conductivities and magneto-optical parameters were performed using the tight binding-linear muffin tin orbitals method within the local spin density approximation. He applied this TB-LMTO method to LuFe{sub 2}. The theoretical results obtained agree well with the experimental data. The oxidation effects on the diagonal part of the optical conductivity were considered using a three-phase model. The oxidation effects on the magneto-optical parameters were also considered by treating the oxide layer as a nonmagnetic thin transparent layer. These corrections change not only the magnitude but also the shape of the optical conductivity and the magneto-optical parameters.

  6. Optical properties of Ho3+-doped NaGd(WO4)2 crystal for laser materials

    International Nuclear Information System (INIS)

    Wang, Hongyan; Li, Jianfu; Jia, Guohua; You, Zhenyu; Yang, Fugui; Wei, Yanping; Wang, Yan; Zhu, Zhaojie; Lu, Xiuai; Tu, Chaoyang

    2007-01-01

    Holmium doped sodium gadolinium tungstate crystals with sizes of about O20 mm x 40 mm were grown successfully by the Czochralski technique along the (0 0 1) orientation. Polarized absorption spectra, fluorescence spectra and fluorescence decay curve of Ho 3+ -doped NaGd(WO 4 ) 2 have been recorded at room temperature. Based on the Judd-Ofelt theory, three intensity parameters were obtained. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetimes as well as the branching ratios were calculated. The fluorescence lifetime τ f of the 5 S 2 level was measured to be 5 μs

  7. Prediction of molecular crystal structures

    International Nuclear Information System (INIS)

    Beyer, Theresa

    2001-01-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of paracetamol (acetaminophen), the influence of the variations of the molecular model on the crystal structure lattice energy minima, has also been studied. The general problem of prediction methods based on the assumption that the experimental thermodynamically stable polymorph corresponds to the global lattice energy minimum, is that more hypothetical low lattice energy structures are found within a few kJ mol -1 of the global minimum than are likely to be experimentally observed polymorphs. This is illustrated by the results for molecule I, 3-oxabicyclo(3.2.0)hepta-1,4-diene, studied for the first international blindtest for small organic crystal structures organised by the Cambridge Crystallographic Data Centre (CCDC) in May 1999. To reduce the number of predicted polymorphs, additional factors to thermodynamic criteria have to be considered. Therefore the elastic constants and vapour growth morphologies have been calculated for the lowest lattice energy

  8. Prediction of molecular crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Theresa

    2001-07-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of paracetamol (acetaminophen), the influence of the variations of the molecular model on the crystal structure lattice energy minima, has also been studied. The general problem of prediction methods based on the assumption that the experimental thermodynamically stable polymorph corresponds to the global lattice energy minimum, is that more hypothetical low lattice energy structures are found within a few kJ mol{sup -1} of the global minimum than are likely to be experimentally observed polymorphs. This is illustrated by the results for molecule I, 3-oxabicyclo(3.2.0)hepta-1,4-diene, studied for the first international blindtest for small organic crystal structures organised by the Cambridge Crystallographic Data Centre (CCDC) in May 1999. To reduce the number of predicted polymorphs, additional factors to thermodynamic criteria have to be considered. Therefore the elastic constants and vapour growth morphologies have been calculated for the lowest lattice energy

  9. Structural characteristics and corrosion behavior of biodegradable Mg-Zn, Mg-Zn-Gd alloys.

    Science.gov (United States)

    Kubásek, J; Vojtěch, D

    2013-07-01

    In this research, binary Mg-Zn (up to 3 wt% Zn) and ternary Mg-Zn-Gd (up to 3 wt% Gd, 3 wt% Zn) alloys were prepared by induction melting in an argon atmosphere. The structures of these alloys were characterized using light and scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and X-ray fluorescence. In addition, Brinell hardness measurements were taken to supplement these studies. Corrosion behavior was evaluated by immersion tests and potentiodynamic measurements in a physiological solution (9 g/l NaCl). Depending on the composition, structures of the as-cast alloys contained α-Mg dendrites, MgZn, Mg5Gd and Mg3Gd2Zn3 phases. Compared to pure Mg, zinc improved the corrosion resistance of binary Mg-Zn. Gadolinium also improved the corrosion resistance in the case of Mg-1Zn-3Gd alloy. The highest corrosion rate was observed for Mg-3Zn-3Gd alloy. Our results improve the understanding of the relationships between the structure and corrosion behavior of our studied alloy systems.

  10. Structural, spectroscopic, and tunable laser properties of Yb3+ -doped NaGd(WO4)2

    Science.gov (United States)

    Cascales, C.; Serrano, M. D.; Esteban-Betegón, F.; Zaldo, C.; Peters, R.; Petermann, K.; Huber, G.; Ackermann, L.; Rytz, D.; Dupré, C.; Rico, M.; Liu, J.; Griebner, U.; Petrov, V.

    2006-11-01

    Single crystals of Yb3+ -doped NaGd(WO4)2 with up to 20mol% ytterbium content have been grown by the Czochralski technique in air or in N2+O2 atmosphere and cooled to room temperature at different rates (4-250°C/h) . Only the noncentrosymmetric tetragonal space group I4¯ accounts for all reflections observed in the single crystal x-ray diffraction analysis. The distortion of this symmetry with respect to the centrosymmetric tetragonal space group I41/a is much lower for crystals cooled at a fast rate. Na+ , Gd3+ , and Yb3+ ions share the two nonequivalent 2b and 2d sites of the I4¯ structure, but Yb3+ (and Gd3+ ) ions are found preferentially in the 2b site. Optical spectroscopy at low (5K) temperature provides additional evidence of the existence of these two sites contributing to the line broadening. The comparison with the F7/22(n) and F5/22(n') Stark energy levels calculated using the crystallographic Yb-O bond distances allows to correlate the experimental optical bands with the 2b and 2d sites. As a novel uniaxial laser host for Yb3+ , NaGd(WO4)2 is characterized also with respect to its transparency, band-edge, refractive indices, and main optical phonons. Continuous-wave Yb3+ -laser operation is studied at room temperature both under Ti:sapphire and diode laser pumping. A maximum slope efficiency of 77% with respect to the absorbed power is achieved for the π polarization by Ti:sapphire laser pumping in a three-mirror cavity with Brewster geometry. The emission is tunable in the 1014-1079nm spectral range with an intracavity Lyot filter. Passive mode locking of this laser produces 120fs long pulses at 1037.5nm with an average power of 360mW at ≈97MHz repetition rate. Using uncoated samples of Yb:NaGd(WO4)2 at normal incidence in simple two-mirror cavities, output powers as high as 1.45W and slope efficiencies as high as 51% are achieved with different diode laser pump sources.

  11. Effects of Gd substitution on the structural and magnetic properties of strontium hexaferrites

    Science.gov (United States)

    Litsardakis, G.; Manolakis, I.; Serletis, C.; Efthimiadis, K. G.

    2007-09-01

    The effect of Gd substitution in M-type strontium hexaferrites has been examined in two series of samples, (Sr1-xGdx)O·5.25Fe2O3 and Sr1-xGdxFe12-xCoxO19, both prepared by the ceramic method, where x=0-0.40. The samples have been characterized by XRD, VSM and SEM-EDAX techniques. All substituted samples present primarily the hexaferrite structure. Sample (Sr0.95Gd)O·5.25Fe2O3 is single phase. Formation of impurity phases is affected by stoichiometry and presence of Co. In Sr-Gd samples, coercivity showed a maximum value of 305 kA/m (3.8 kOe) for x=0.20, while remanence and saturation magnetization did not decrease. Coercivity and magnetization in the Sr-Gd-Co series decreased steadily with substitution degree.

  12. Crystal structure of cafenstrole

    Directory of Open Access Journals (Sweden)

    Gihaeng Kang

    2015-08-01

    Full Text Available The title compound (systematic name: N,N-diethyl-3-mesitylsulfonyl-1H-1,2,4-triazole-1-carboxamide, C16H22N4O3S, is a triazole herbicide. The dihedral angle between the planes of the triazole and benzene ring planes is 88.14 (10°. In the crystal, C—H...O hydrogen bonds and weak C—H...π interactions link adjacent molecules, forming one-dimensional chains along the a axis.

  13. Crystal structure of pseudoguainolide

    Directory of Open Access Journals (Sweden)

    Noureddine Beghidja

    2015-03-01

    Full Text Available The lactone ring in the title molecule, C15H22O3 (systematic name: 3,4a,8-trimethyldodecahydroazuleno[6,5-b]furan-2,5-dione, assumes an envelope conformation with the methine C atom adjacent to the the methine C atom carrying the methyl substituent being the flap atom. The other five-membered ring adopts a twisted conformation with the twist being about the methine–methylene C—C bond. The seven-membered ring is based on a twisted boat conformation. No specific interactions are noted in the the crystal packing.

  14. Near-infrared and upconversion properties of neodymium-doped RE0.8La0.2VO4 (RE = Y, Gd) single-crystal fibres grown by the laser-heated pedestal growth technique

    International Nuclear Information System (INIS)

    Camargo, A S S de; Nunes, L A O; Andreeta, M R B; Hernandes, A C

    2002-01-01

    Neodymium-doped Y 0.8 La 0.2 VO 4 and Gd 0.8 La 0.2 VO 4 single-crystal fibres were successfully grown by the laser-heated pedestal growth (LHPG) technique. The fibres were completely transparent and no dark inclusions were observed by optical microscopy. In the characterization process, microprobe Raman, optical absorption, fluorescence, lifetime, and gain-excited state absorption spectra were investigated in addition to upconversion measurements. The fibres' structural and spectroscopic properties are very similar to those of YVO 4 and GdVO 4 bulk laser crystals, with the advantageous characteristic of broadened spectral linewidths that facilitate the pumping of the 1064 nm emission by a diode laser. These fairly new crystal compositions, that can be grown in fast and economical processes, are potential candidates for use as compact laser-active media

  15. Effects of Gd substitution on the structural and magnetic properties of strontium hexaferrites

    Energy Technology Data Exchange (ETDEWEB)

    Litsardakis, G. [Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)]. E-mail: Lits@eng.auth.gr; Manolakis, I. [Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Serletis, C. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Efthimiadis, K.G. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)

    2007-09-15

    The effect of Gd substitution in M-type strontium hexaferrites has been examined in two series of samples, (Sr{sub 1-x}Gd{sub x})O.5.25Fe{sub 2}O{sub 3} and Sr{sub 1-x}Gd{sub x}Fe{sub 12-x}Co{sub x}O{sub 19}, both prepared by the ceramic method, where x=0-0.40. The samples have been characterized by XRD, VSM and SEM-EDAX techniques. All substituted samples present primarily the hexaferrite structure. Sample (Sr{sub 0.95}Gd{sub x0.05})O.5.25Fe{sub 2}O{sub 3} is single phase. Formation of impurity phases is affected by stoichiometry and presence of Co. In Sr-Gd samples, coercivity showed a maximum value of 305kA/m (3.8kOe) for x=0.20, while remanence and saturation magnetization did not decrease. Coercivity and magnetization in the Sr-Gd-Co series decreased steadily with substitution degree.

  16. Comparative optical study of thulium-doped YVO4 , GdVO4 , and LuVO4 single crystals

    Science.gov (United States)

    Lisiecki, R.; Solarz, P.; Dominiak-Dzik, G.; Ryba-Romanowski, W.; Sobczyk, M.; Černý, Pavel; Šulc, Jan; Jelínková, Helena; Urata, Yoshiharu; Higuchi, Mikio

    2006-07-01

    YVO4:Tm3+ crystals grown by the Czochralski technique and GdVO4:Tm3+ and LuVO4:Tm3+ crystals grown by the floating-zone technique were investigated using methods of optical spectroscopy. Polarized absorption and emission spectra were recorded at room temperature and at 6K . The crystal-field analysis was performed assuming the D2d site symmetry for Tm3+ ions. In this way the missing crystal-field components of the H63 ground multiplet were located. Room temperature absorption spectra were analyzed in the framework of the Judd-Ofelt theory. Evaluated radiative lifetimes of luminescent levels of Tm3+ follow a general trend diminishing in agreement with the sequence: YVO4:Tm3+→GdVO4:Tm3+→LuVO4:Tm3+ . Luminescence lifetimes measured for the systems under study are similar except for the F43 lifetime, which appears to be surprisingly short for LuVO4:Tm3+ . Anisotropy of optical spectra is particularly pronounced in LuVO4:Tm3+ . Peak absorption cross section for the band relevant for optical pumping at about 805nm is roughly three times higher for π polarization. Stimulated emission cross sections for the F43-H63 transition near 1800nm were evaluated using the reciprocity method. The diode-pumped continuous wave laser operation in GdVO4:Tm3+ with a slope efficiency of up to 40% is demonstrated. In LuVO4:Tm3+ the diode-pumped laser oscillation in a pulsed mode was observed.

  17. Energy transfer phenomena and Judd-Ofelt analysis on Sm{sup 3+} ions in K{sub 2}GdF{sub 5} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Do, Phan Van [Thuyloi University, 175 Tay Son, Dong da Dist, Hanoi (Viet Nam); Tuyen, Vu Phi, E-mail: vptuyen@gust-edu.vast.vn [Graduate University of Science and Technology - VAST, 18 Hoang quoc Viet, Hanoi (Viet Nam); DuyTan University, K7/25 QuangTrung, Danang (Viet Nam); Quang, Vu Xuan [DuyTan University, K7/25 QuangTrung, Danang (Viet Nam); Khaidukov, Nicholas M. [Kurnakov Institute of General and Inorganic Chemistry, Moscow (Russian Federation); TrongThanh, Nguyen [Institute of Materials Science - VAST, 18 Hoang quoc Viet, Hanoi (Viet Nam); Sengthong, Bounyavong [DuyTan University, K7/25 QuangTrung, Danang (Viet Nam); Huy, Bui The, E-mail: buithehuy.nt@gmail.com [Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of)

    2016-11-15

    The Raman, absorption, luminescence spectra and lifetimes curves of Sm{sup 3+}-doped K{sub 2}GdF{sub 5}were measured. Based on the Judd-Ofelt analysis, the values of radiative transition probabilities, branching ratios, integrated emission cross-sections and radiative lifetimes of excited states of Sm{sup 3+} in K{sub 2}GdF{sub 5} crystal were calculated. The migration of excitation energy between the Gd{sup 3+} ions and the trapping processes of Gd{sup 3+} excitation energy by Sm{sup 3+} and Tb{sup 3+}ions in K{sub 2}GdF{sub 5} crystal are reported. The role of the overlapping between the broad, allowed absorption bands of the RE{sup 3+} ions and the narrow absorption lines {sup 6}I{sub J} and {sup 6}P{sub J} of Gd{sup 3+} ions on the trapping rates of the RE{sup 3+} was discussed. The energy transfer between the Sm{sup 3+} ions was studied by the decay measurement, which has been fitted by Inokuti-Hirayama energy transfer model and revealed that electric dipole–quadrupole interaction is responsible for the energy transfer process in Sm{sup 3+} ions doped K{sub 2}GdF{sub 5} crystal.

  18. New intermetallic compounds Ln(Ag, AL)4 (Ln-Y, Gd, Tb, Dy) and their structure

    International Nuclear Information System (INIS)

    Kuz'ma, Yu.B.; Stel'makhovich, B.M.

    1990-01-01

    By the methods of X-ray analysis crystal structure of compounds Ln(Ag,Al) 4 , where Ln-Y, Gd, Tb, Dy, posessing rhombic structure, is determined. The intermetallics have been prepared for the first time. Ways of atom distribution and their coordinates in DyAg 0.55 Al 3.45 structure (a=0.4296(1), b=04179(1), c=0.9995(3), R=0.093) are specified. Other compounds are formed in case of LnAgAl 3 compositions. Interatomic distances in Dy(Ag,Al) 4 structure are considered. A supposition is made on the formation in Ln-Ag-Al systems of a greater number of intermetallic compounds

  19. Crystal structure refinement with SHELXL

    Energy Technology Data Exchange (ETDEWEB)

    Sheldrick, George M., E-mail: gsheldr@shelx.uni-ac.gwdg.de [Department of Structural Chemistry, Georg-August Universität Göttingen, Tammannstraße 4, Göttingen 37077 (Germany)

    2015-01-01

    New features added to the refinement program SHELXL since 2008 are described and explained. The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as ‘a CIF’) containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.

  20. Crystal structure of pymetrozine

    Directory of Open Access Journals (Sweden)

    Youngeun Jeon

    2015-07-01

    Full Text Available The title compound, C10H11N5O {systematic name: 6-methyl-4-[(E-(pyridin-3-ylmethylideneamino]-4,5-dihydro-1,2,4-triazin-3(2H-one}, C10H11N5O, is used as an antifeedant in pest control. The asymmetric unit comprises two independent molecules, A and B, in which the dihedral angles between the pyridinyl and triazinyl ring planes [r.m.s. deviations = 0.0132 and 0.0255 ] are 11.60 (6 and 18.06 (4°, respectively. In the crystal, N—H...O, N—H...N, C—H...N and C—H...O hydrogen bonds, together with weak π–π interactions [ring-centroid separations = 3.5456 (9 and 3.9142 (9 Å], link the pyridinyl and triazinyl rings of A molecules, generating a three-dimensional network.

  1. Influence of Y, Gd and Sm on the glass forming ability and thermal crystallization of aluminum based alloy; Efeito das terras raras Y, Gd e Sm na tendencia a formacao de amorfo e na cristalizacao termica em ligas a base de aluminio

    Energy Technology Data Exchange (ETDEWEB)

    Aliaga, L.C.R.; Bolfarini, C.; Kiminami, C.S.; Botta Filho, W.J., E-mail: aliaga@ufscar.b [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais; Danez, G.P. [Universidade Federal de Sao Carlos (PPG-CEMUFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais

    2010-07-01

    Al-based amorphous alloys represent an important family of metals and a great scientific activity has been devoted to determine the main features of both glass forming ability (GFA) and crystallization behavior in order to have a comprehensive framework aimed at potential technological applications. Nowadays, it is well known that the best Al-based amorphous alloys are formed in ternary systems such as Al- RE-TM, where RE is a rare earth and TM a transition metal. This paper presents results of research in Al{sub 85}Ni{sub 10}RE{sub 5} alloys (RE = Y, Gd and Sm). Amorphous ribbons were processed by melt-spinning under the same conditions and subsequently characterized by x-ray diffraction (XRD) and differential scanning calorimetry (DSC). Results show appreciable micro structural differences as function of the rare earth, thus crystal is obtained for Y, nano-glassy for Gd and, fully amorphous structure for Sm. (author)

  2. Crystal Chemistry and Photocatalytic Properties of RE4S4Te3 (RE = Gd, Ho, Er, Tm): Experimental and Theoretical Investigations.

    Science.gov (United States)

    Chi, Yang; Rong, Liang-Zhen; Suen, Nian-Tzu; Xue, Huai-Guo; Guo, Sheng-Ping

    2018-04-25

    Reported are the synthesis and structural characterization of a new series of ternary rare-earth mix-chalcogenides RE 4 S 4 Te 3 (RE = Gd, Ho, Er, Tm) that have been obtained from high-temperature solid state reactions. These compounds crystallize in Ho 4 S 4 Te 2.68 structure types with monoclinic C2/ m and/or orthorhombic Immm space groups. The space group variation within this series is due to the position disorder along the Te plane (Te to TeA and TeB). The structural relationship and change between these two space groups are analyzed. It is realized that these compounds are all photocatalytic active under simulated sunlight. The trend of their photocatalytic activities and photocurrent responses is well-explained by using theoretical calculation as well as dipole moment analysis.

  3. Single-crystal-like GdNdO{sub x} thin films on silicon substrates by magnetron sputtering and high-temperature annealing for crystal seed layer application

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ziwei; Xiao, Lei; Liang, Renrong, E-mail: wang-j@tsinghua.edu.cn, E-mail: liangrr@tsinghua.edu.cn; Shen, Shanshan; Xu, Jun; Wang, Jing, E-mail: wang-j@tsinghua.edu.cn, E-mail: liangrr@tsinghua.edu.cn [Tsinghua National Laboratory for Information Science and Technology, Institute of Microelectronics, Tsinghua University, Beijing 100084 (China)

    2016-06-15

    Single-crystal-like rare earth oxide thin films on silicon (Si) substrates were fabricated by magnetron sputtering and high-temperature annealing processes. A 30-nm-thick high-quality GdNdO{sub x} (GNO) film was deposited using a high-temperature sputtering process at 500°C. A Gd{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} mixture was used as the sputtering target, in which the proportions of Gd{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} were controlled to make the GNO’s lattice parameter match that of the Si substrate. To further improve the quality of the GNO film, a post-deposition annealing process was performed at a temperature of 1000°C. The GNO films exhibited a strong preferred orientation on the Si substrate. In addition, an Al/GNO/Si capacitor was fabricated to evaluate the dielectric constant and leakage current of the GNO films. It was determined that the single-crystal-like GNO films on the Si substrates have potential for use as an insulator layer for semiconductor-on-insulator and semiconductor/insulator multilayer applications.

  4. Single-crystal-like GdNdOx thin films on silicon substrates by magnetron sputtering and high-temperature annealing for crystal seed layer application

    Directory of Open Access Journals (Sweden)

    Ziwei Wang

    2016-06-01

    Full Text Available Single-crystal-like rare earth oxide thin films on silicon (Si substrates were fabricated by magnetron sputtering and high-temperature annealing processes. A 30-nm-thick high-quality GdNdOx (GNO film was deposited using a high-temperature sputtering process at 500°C. A Gd2O3 and Nd2O3 mixture was used as the sputtering target, in which the proportions of Gd2O3 and Nd2O3 were controlled to make the GNO’s lattice parameter match that of the Si substrate. To further improve the quality of the GNO film, a post-deposition annealing process was performed at a temperature of 1000°C. The GNO films exhibited a strong preferred orientation on the Si substrate. In addition, an Al/GNO/Si capacitor was fabricated to evaluate the dielectric constant and leakage current of the GNO films. It was determined that the single-crystal-like GNO films on the Si substrates have potential for use as an insulator layer for semiconductor-on-insulator and semiconductor/insulator multilayer applications.

  5. Polarized spectral properties of Yb3+ : Li2Gd4(MoO4)7 crystal: a candidate for tunable and ultrashort pulse lasers

    International Nuclear Information System (INIS)

    Zhu Haomiao; Chen Yujin; Lin Yanfu; Gong Xinghong; Liao Jinsheng; Chen Xueyuan; Luo Zundu; Huang Yidong

    2007-01-01

    Detailed polarized spectral properties of a 3.2 at.% Yb 3+ : Li 2 Gd 4 (MoO 4 ) 7 crystal, including absorption cross-section, emission cross-section, up-conversion spectrum and intrinsic fluorescence lifetime, were investigated. The laser potentiality was also evaluated and the results show that this crystal is a good candidate for tunable and ultrashort pulse lasers

  6. X-ray absorption in GaGdN: A study of local structure

    Science.gov (United States)

    Martínez-Criado, G.; Sancho-Juan, O.; Garro, N.; Sans, J. A.; Cantarero, A.; Susini, J.; Roever, M.; Mai, D.-D.; Bedoya-Pinto, A.; Malindretos, J.; Rizzi, A.

    2008-07-01

    In this study, we report on the incorporation of dilute Gd amounts into GaN films grown by molecular beam epitaxy. A combination of x-ray fluorescence with x-ray absorption spectroscopic techniques enabled us to examine not only the distribution of rare earth atoms in the GaN matrix but also the short-range structural order. Our results show Gd atoms in a trivalent state with tetrahedral coordination, thus substituting Ga in the wurtzite GaN structure.

  7. X-ray absorption in GaGdN: A study of local structure

    International Nuclear Information System (INIS)

    Martinez-Criado, G.; Sans, J. A.; Susini, J.; Sancho-Juan, O.; Cantarero, A.; Garro, N.; Roever, M.; Mai, D.-D.; Bedoya-Pinto, A.; Malindretos, J.; Rizzi, A.

    2008-01-01

    In this study, we report on the incorporation of dilute Gd amounts into GaN films grown by molecular beam epitaxy. A combination of x-ray fluorescence with x-ray absorption spectroscopic techniques enabled us to examine not only the distribution of rare earth atoms in the GaN matrix but also the short-range structural order. Our results show Gd atoms in a trivalent state with tetrahedral coordination, thus substituting Ga in the wurtzite GaN structure

  8. Structural and dielectric properties of Gd doped bismuth ferrite-lead titanate

    International Nuclear Information System (INIS)

    Mohanty, N. K.; Behera, A. K.; Satpathy, S. K.; Behera, B.; Nayak, P.

    2014-01-01

    0.5BiGd x Fe 1−x O 3 −0.5PbTiO 3 with x=0.05, 0.10, 0.15, 0.20 composite was prepared by mixed oxide method. Structural characterization was performed by X-ray diffraction and studied that the materials show tetragonal structure at room temperature for all concentration of Gd. Studies of dielectric properties (ε r and tanδ) of the above compound at different frequencies in a wide range of temperature (25°-500°C) with an impedance analyser revealed that the dielectric constant increases with increase in Gd concentration as well temperature and the compound do not have any dielectric anomaly in the studied frequency and temperature range

  9. Tunable paramagnetic relaxation enhancements by [Gd(DPA)3]3- for protein structure analysis

    International Nuclear Information System (INIS)

    Yagi, Hiromasa; Loscha, Karin V.; Su, Xun-Cheng; Stanton-Cook, Mitchell; Huber, Thomas; Otting, Gottfried

    2010-01-01

    Paramagnetic relaxation enhancements (PRE) present a powerful source of structural information in nuclear magnetic resonance (NMR) studies of proteins and protein-ligand complexes. In contrast to conventional PRE reagents that are covalently attached to the protein, the complex between gadolinium and three dipicolinic acid (DPA) molecules, [Gd(DPA) 3 ] 3- , can bind to proteins in a non-covalent yet site-specific manner. This offers straightforward access to PREs that can be scaled by using different ratios of [Gd(DPA) 3 ] 3- to protein, allowing quantitative distance measurements for nuclear spins within about 15 A of the Gd 3+ ion. Such data accurately define the metal position relative to the protein, greatly enhancing the interpretation of pseudocontact shifts induced by [Ln(DPA) 3 ] 3- complexes of paramagnetic lanthanide (Ln 3+ ) ions other than gadolinium. As an example we studied the quaternary structure of the homodimeric GCN4 leucine zipper.

  10. Spectral properties of Er{sup 3+}-doped CaGdAlO{sub 4} crystal for laser application around 1.55 μm

    Energy Technology Data Exchange (ETDEWEB)

    Huang, J.H.; Gong, X.H.; Chen, Y.J.; Lin, Y.F; Luo, Z.D.; Huang, Y.D., E-mail: huyd@fjirsm.ac.cn

    2014-02-05

    Highlights: • Detailed spectral properties of the Er:CaGdAlO{sub 4} crystal have been investigated. • Multi-phonon relaxation rate of Er{sup 3+} ions in the Er:CaGdAlO{sub 4} crystal is estimated. • The quantum efficiency of the {sup 4}I{sub 13/2} level in the Er:CaGdAlO{sub 4} crystal is near 100%. -- Abstract: Room-temperature polarized spectral properties of the Er:CaGdAlO{sub 4} crystal are reported. The Judd–Ofelt theory was applied to analyze the polarized absorption spectra and then calculate the spontaneous emission probabilities, radiative lifetimes, and branch ratios. Room-temperature fluorescence lifetimes of the {sup 4}I{sub 13/2}, {sup 4}I{sub 11/2}, {sup 4}F{sub 9/2}, and {sup 4}S{sub 3/2} multiplets for Er{sup 3+} ions were measured. Stimulated emission cross-sections of the {sup 4}I{sub 13/2} → {sup 4}I{sub 15/2} transition obtained by the Fuchtbauer–Ladenberg formula and the reciprocity method were compared. The results show that the Er:CaGdAlO{sub 4} crystal may be a potential gain medium for a low-threshold 1.55 μm laser.

  11. Comparative study of crystallographic, spectroscopic, and laser properties of Tm3+ in NaT(WO4)2 (T=La, Gd, Y, and Lu) disordered single crystals

    Science.gov (United States)

    Cano-Torres, J. M.; Rico, M.; Han, X.; Serrano, M. D.; Cascales, C.; Zaldo, C.; Petrov, V.; Griebner, U.; Mateos, X.; Koopmann, P.; Kränkel, C.

    2011-11-01

    Tetragonal double tungstate single crystals with formula NaT(WO4)2 have been grown by the Czochralski (T = Gd, La, Y) or by the top-seeded solution growth (T = Lu) methods with Tm concentration between 8 × 1018 and 7.85 × 1020 cm-3. The spectroscopic properties of Tm3+ in these crystals are related with the peculiarities of their I4¯ crystalline structure. Sixty-five percent of La ions in NaLa(WO4)2 are in the 2d site, while in the other crystal hosts, the lanthanide occupies preferentially the 2b site (59% in T = Gd, 74% in T = Y, and 58% in T = Lu). As a consequence, the linewidths of spectral bands associated with the electronic transitions are significantly narrower in NaLa(WO4)2 than in the rest of the isostructural crystals considered. Polarized spectroscopic measurements at 5 K and at higher temperatures, along with energy level simulation of the 4f12 configuration using a single-electron Hamiltonian, including free-ion and crystal field interactions, allowed us to determine the irreducible representation and energy of Stark levels up to the 3P0 multiplet and thus to obtain realistic partition functions (Z) used for emission cross-section calculations. In particular, for the 3F4(u) → 3H6(l) laser transition at λ ≈ 2 μm, this provides: Zl/Zu = 1.436 (T = Gd), 1.464 (T = La), 1.448 (T = Y), and 1.471 (T = Lu). Radiative lifetimes calculated by the Judd-Ofelt and Füchtbauer-Ladenburg methods are in agreement and decrease in the following order T = Gd, La, Y, and Lu, however, nonradiative losses are stronger for T = Gd and La crystals; therefore, experimental lifetimes of 1D2, 1G4, 3H4, and 3F4 Tm3+ multiplets do not change too much with crystal host. For 4.68 at.% Tm:NaY(WO4)2 crystal continuous-wave laser operation is obtained with ≈42% of slope efficiency and a record (for this crystal class) tuning capability of λ = 1847-2069 nm. The broad bandwidths, ΔλFWHM > 20 nm, of the free-running laser emission are promising for ultrafast (fs) mode

  12. Linear optical properties of Ca4EuO(BO3)3 and Eu3+ : Ca4GdO(BO3)3 crystals

    International Nuclear Information System (INIS)

    Antic-Fidancev, E.; Lemaitre-Blaise, M.; Porcher, P.; Caramanian, A.; Aka, G.

    1998-01-01

    Full text: The title compounds are now intensively studied due to their quadratic nonlinear properties in view of applications, e.g. high power laser frequency conversion. Rare earth calcium oxoborates, Ca 4 REO(BO 3 ) 3 , constitute an isostructural family along the rare earth series with RE = La - Lu, Y included. These compounds crystallize in the monoclinic biaxial crystal system with Cm (N 8) space group. They are isostructural to the calcium fluoroborate Ca 5 (BO 3 ) 3 F which is related to the fluoroapatite structure Ca 5 (PO 4 ) 3 F. The rare earth ions are located in the distorted octahedron with C s point site symmetry in the mirror plane. Two types of distorted octahedral sites exist for calcium ions. The existence of some disorder between calcium and rare earth atoms is suspected from the structural analysis. Good optical quality crystals of europium (or gadolinium) oxoborate, EuCOB (GdCOB) have been grown from the stoichiometric melt by the Czochralski pulling method. From the luminescence of the Eu 3+ doped gadolinium or in the europium stoichiometric compound very complex emission spectra have been obtained. It principally depends on the preparation method of studied samples: i) for a monocrystalline sample, a single phase with a single site is observed; ii) for a polycrystalline sample complex feature occurs. It is probably due to an expanded disorder between calcium and rare earth atoms. Practically, there is one principal site corresponding to the low symmetry site of the rare earth as expected from the structural investigation. Other minor sites are attributed to the local distortion created around the active rare earth ion. The intensity of the emission lines of Eu 3+ used as a local structural probe related to these minor sites increases when the gadolinium in Ca 4 GdO(BO 0 ) 3 is substituted by lanthanum or yttrium ions. It seems therefore evident that the synthesis of these rare earth calcium oxoborates must be realised carefully. The crystal

  13. Micro structural and magnetic characterization of Gd doped SnO2 nanoparticles

    International Nuclear Information System (INIS)

    Adhikari, R.; Das, A.K.; Karmakar, D.; Chandrasekhar Rao, T.V.; Ghatak, J.

    2008-01-01

    Gd doped SnO 2 nanoparticles were prepared by a chemical co-precipitation method. The prepared samples were calcined at 600 deg C. The annealed samples were characterized using XRD, TEM and SQUID magnetometry. The structural characterizations showed formation of particles in the nanometer regime. The M(T) and M(H) studies indicated an antiferromagnetic (AFM) interaction in 3 and 6% (at. wt.) Gd doped SnO 2 nanoparticles. The M(H) plot of both samples indicate a super paramagnetic (SPM) behavior at 7K as against the perfect AFM nature at 300K. The samples exhibit an insulating DMS nature, but we do not observe any ferromagnetism as was observed for other Gd doped systems like GaN and ZnO. (author)

  14. Electrical and structural properties of GdBa2Cu3-xVxO7-x

    International Nuclear Information System (INIS)

    Javanmard, H.; Bazargan, S.; Akhavan, M.

    2007-01-01

    Full text: It is well known that the characteristics of the CuO 2 planes are essential for understanding the unconventional superconductivity and the anomalous transport behavior of the normal state in cuprate superconductors. Continuous efforts have been devoted to the study of effects of substitution for Cu, which are of great importance for understanding the role of Cu in high-Tc superconductivity. The bulk samples of GdBa 2 Cu 3-x V x O 7-x with 0.0 4+ in the compound, and because of the high tendency of the V 4+ for achieving the octahedral structure, it appears that vanadium enters the chains, which accounts for the observed changes in the crystal structure and superconducting properties. (authors)

  15. Spectroscopic study of magnetic phase transitions and magnetic structures in rare earth ferroborates RFe3(BO3)4 (R = Y, Er, Tb, Gd)

    International Nuclear Information System (INIS)

    Popova, M.N.; Chukalina, E.P.; Stanislavchuk, T.N.; Bezmaternykh, L.N.

    2006-01-01

    One investigated into the absorption spectra of RFe 3 (BO 3 ) 4 , R=Y, Er, Tb, Gd rare earth borate single crystals containing erbium (1%) introduced to serve as a probe. On the basis of the temperature dependences of Er 3+ ion spectral line splittings one determined the values of the magnetic ordering temperatures of Er, Tb and Gd ferroborates and the temperatures of the spin reoriented first order phase transition in GdFe 3 (BO 3 ) 4 :Er 3+ (1%). On the basis of comparison of the splitting values of Er 3+ ion ground state in RFe 3 (BO 3 ) 4 (R=Y, Er, Tb) and in GdFe 3 (BO 3 )4 compounds the magnetic structure of which is known one makes a concussion about the orientation of iron magnetic moments in the magneto-ordered state: a lightly planar structure is observed for YFe 3 (BO 3 ) 4 and ErFe 3 (BO 3 ) 4 and a lightly axial one - for TbFe 3 (BO 3 ) 4 . One discusses the role of R 3+ ion single ion anisotropy when determining the magnetic structure type in RFe 3 (BO 3 ) 4 [ru

  16. Influence of hydrogenation and mechanical grinding on the structural and ferromagnetic properties of GdFeSi

    Energy Technology Data Exchange (ETDEWEB)

    Chevalier, Bernard; Duttine, Mathieu; Wattiaux, Alain [Universite de Bordeaux, CNRS ICMCB, Pessac (France)

    2016-08-01

    Hydrogen insertion into GdFeSi induces (i) a structural transition from a tetragonal CeFeSi-type to a tetragonal ZrCuSiAs-type, (ii) an anisotropic expansion of the unit cell parameters because the a parameter decreases, whereas the c parameter increases, and (iii) a decrease in Curie temperature from 121 to 20 K. On the contrary, an amorphous ferromagnet (T{sub C} = 65 K) is obtained by mechanical grinding of GdFeSi. The three compounds (GdFeSi, GdFeSiH, and amorphous GdFeSi) were investigated by {sup 57}Fe Moessbauer spectroscopy. At 4.2 K, this study has revealed that the magnetically ordered Gd substructure produces a small transferred hyperfine magnetic field at the {sup 57}Fe nucleus.

  17. Structural phase transitions at high-temperature in double perovskite Sr{sub 2}GdRuO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Triana, C.A.; Corredor, L.T.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A.A. 14490, Bogota D.C (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A.A. 14490, Bogota D.C (Colombia)

    2012-08-15

    The crystal structure evolution of the Sr{sub 2}GdRuO{sub 6} complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K{<=}T{<=}1273 K. Powder X-ray diffraction measurements at room temperature and Rietveld analysis show that this compounds crystallizes in a monoclinic perovskite-type structure with P2{sub 1}/n (no. 14) space group and the 1:1 ordered arrangement of Ru{sup 5+} and Gd{sup 3+} cations over the six-coordinate M sites, with lattice parameters a=5.81032(8) A, b=5.82341(4) A, c=8.21939(7) A, V=278.11(6) A{sup 3} and angle {beta}=90.311(2){sup o}. The high-temperature analysis shows that this material suffers two-phase transitions. At 373 K it adopts a monoclinic perovskite structure with I2/m space group, and lattice parameters a=5.81383(2) A, b=5.82526(4) A, c=8.22486(1) A, V=278.56(2) A{sup 3} and angle {beta}=90.28(2){sup o}. Above of 773 K, it suffers a phase transition from monoclinic I2/m to tetragonal I4/m, with lattice parameters a=5.84779(1) A, c=8.27261(1) A, V=282.89(5) A{sup 3} and angle {beta}=90.02(9){sup o}. The high-temperature phase transition from monoclinic I2/m to tetragonal I4/m is characterized by strongly anisotropic displacements of the anions.

  18. β-Y(BO{sub 2}){sub 3}. A new member of the β-Ln(BO{sub 2}){sub 3} (Ln = Nd, Sm, Gd-Lu) structure family

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Martin K.; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie

    2017-07-01

    β-Y(BO{sub 2}){sub 3} was synthesized in a Walker-type multianvil module at 5.9 GPa/1000 C. The crystal structure has been elucidated through single-crystal X-ray diffraction. β-Y(BO{sub 2}){sub 3} crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 15.886(2), b = 7.3860(6), and c = 12.2119(9) Aa. Its crystal structure will be discussed in the context of the isotypic lanthanide borates β-Ln(BO{sub 2}){sub 3} (Ln = Nd, Sm, Gd-Lu).

  19. Luminescence and scintillation timing characteristics of (Lu{sub x}Gd{sub 2−x})SiO{sub 5}:Ce single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yawai, Nattasuda; Chewpraditkul, Warut; Sakthong, Ongsa [Faculty of Science, King Mongkut' s University of Technology Thonburi, Bangkok10140 (Thailand); Chewpraditkul, Weerapong, E-mail: weerapong.che@kmutt.ac.th [Faculty of Science, King Mongkut' s University of Technology Thonburi, Bangkok10140 (Thailand); Wantong, Kriangkrai [Faculty of Science, King Mongkut' s University of Technology Thonburi, Bangkok10140 (Thailand); Szczesniak, Tomasz; Swiderski, Lukasz; Moszynski, Marek [National Centre for Nuclear Research, A. Soltana 7, PL 05-400 Otwock-Swierk (Poland); Sidletskiy, Oleg [Institute for Scintillation Materials NAS of Ukraine, 60 Nauky Avenue, 61001 Kharkiv (Ukraine)

    2017-02-01

    The luminescence and scintillation characteristics of cerium-doped lutetium-gadolinium orthosilicate (Lu{sub x}Gd{sub 2−x}SiO{sub 5}:Ce; x=0, 0.8, 1.8) single crystals were investigated. At 662 keV γ-rays, the light yield of 29,800±3000 ph MeV{sup −1} obtained for Lu{sub 1.8}Gd{sub 0.2}SiO{sub 5}:Ce is higher than that of 20,200±2000 and 11,800±1200 ph MeV{sup −1} obtained for Lu{sub 0.8}Gd{sub 1.2}SiO{sub 5}:Ce and Gd{sub 2}SiO{sub 5}:Ce, respectively. The fast component decay time of 32, 18 and 17 ns was measured in the scintillation decay of Gd{sub 2}SiO{sub 5}:Ce, Lu{sub 0.8}Gd{sub 1.2}SiO{sub 5}:Ce and Lu{sub 1.8}Gd{sub 0.2}SiO{sub 5}:Ce, respectively. The coincidence time spectra for 511 keV annihilation quanta were measured in reference to a fast BaF{sub 2} detector and time resolution was discussed in terms of a number of photoelectrons and decay time of the fast component. The mass attenuation coefficient for studied crystals at 60 and 662 keV γ-rays was also evaluated and discussed. - Highlights: • Scintillation timing characteristics of Lu{sub x}Gd{sub 2−x}SiO{sub 5}:Ce crystals are studied. • Lu{sub 1.8}Gd{sub 0.2}SiO{sub 5}:Ce exhibits excellent light yield and timing response. • Energy resolution of 6% @662 keV is obtained for Lu{sub 0.8}Gd{sub 1.2}SiO{sub 5}:Ce. • Coincidence time resolution of 368 ps is obtained for Lu{sub 1.8}Gd{sub 0.2}SiO{sub 5}:Ce.

  20. Structural, magnetic, and electrical properties of Gd-doped BiFeO3 nanoparticles with reduced particle size

    International Nuclear Information System (INIS)

    Lotey, Gurmeet Singh; Verma, N. K.

    2012-01-01

    Pure and Gd-doped BiFeO 3 nanoparticles have been synthesized by sol–gel method. The significant effects of size and Gd-doping on structural, electrical, and magnetic properties have been investigated. X-ray diffraction study reveals that the pure BiFeO 3 nanoparticles possess rhombohedral structure, but with 10% Gd-doping complete structural transformation from rhombohedral to orthorhombic has been observed. The particle size of pure and Gd-doped BiFeO 3 nanoparticles, calculated using Transmission electron microscopy, has been found to be in the range 25–15 nm. Pure and Gd-doped BiFeO 3 nanoparticles show ferromagnetic character, and the magnetization increases with decrease in particle size and increase in doping concentration. Scanning electron microscopy study reveals that grain size decreases with increase in Gd concentration. Well-saturated polarization versus electric field loop is observed for the doped samples. Leakage current density decreases by four orders by doping Gd in BiFeO 3 . The incorporation of Gd in BiFeO 3 enhances spin as well as electric polarization at room temperature. The possible origin of enhancement in these properties has been explained on the basis of dopant and its concentration, phase purity, small particle, and grain size.

  1. Crystal structure and magnetic susceptibility of UOSe single crystals

    International Nuclear Information System (INIS)

    Kaczorowski, D.; Muenster Univ.; Poettgen, R.; Jeitschko, W.; Gajek, Z.; Zygmunt, A.

    1993-01-01

    The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T N =100±2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author)

  2. Crystal structure and magnetic susceptibility of UOSe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kaczorowski, D. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Poettgen, R.; Jeitschko, W. (Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Gajek, Z.; Zygmunt, A. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research)

    1993-01-01

    The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T[sub N]=100[+-]2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author).

  3. Structural evolution and electrical properties of BaTiO{sub 3} doped with Gd{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez Lara, Juan Pablo; Perez Labra, Miguel; Barrientos Hernandez, Francisco Raul, E-mail: miguelabra@hotmail.com [Autonomous University of Hidalgo (Mexico); Romero Serrano, Jose Antonio; Hernandez Ramirez, Aurelio [Metallurgy and Materials Department, ESIQIE-IPN, UPALM, Zacatenco (Mexico); Avila Davila, Erika Osiris [Mechanical Engineering Department, Technological Institute of Pachuca, Hidalgo (Mexico); Thangarasu, Pandiyan [Facultad de Quimica, UNAM, Mexico D.F. (Mexico)

    2017-03-15

    BaTiO{sub 3} doped with Gd{sup 3+} (Ba{sub 1-x}Gd{sub x}Ti{sub 1-x/4}O{sub 3}) was synthesized using the solid-state reaction method with x = 0.001, 0.003, 0.005, 0.01, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, and 0.35 Gd{sup 3+} (wt. %). The powders were decarbonated at 900 °C and sintered at 1400 °C for 8 hours. The tetragonality of the synthesized Gd{sup 3+}-doped BaTiO{sub 3} particles was analyzed. XRD patterns and Raman spectra revealed that the crystal phase of the obtained particles was predominately tetragonal BaTiO{sub 3}; the intensity of the Raman bands at 205 cm{sup -1}, 265 cm{sup -1}, and 304 cm{sup -1} decreased when Gd'3{sup +} was increased. A secondary phase (Gd{sub 2}Ti{sub 2}O{sub 7}) was found when the Gd{sup 3+} content was higher than 0.15 wt. %. The capacitance of the sintering pellets was measured at 1 kHz; these values were used to calculate the relative permittivity, the maximum permittivity values were recorded for the samples with x = 0.001, 0.005, and 0.1. (author)

  4. Polarized spectroscopic properties of Er{sup 3+}:Gd{sub 2}SiO{sub 5} crystal and evaluation of Er{sup 3+}:Yb{sup 3+}:Gd{sub 2}SiO{sub 5} crystal as a 1.55 μm laser medium

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H. [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Huang, J.H.; Gong, X.H.; Chen, Y.J.; Lin, Y.F.; Luo, Z.D. [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Huang, Y.D., E-mail: huyd@fjirsm.ac.cn [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

    2016-10-01

    An Er{sup 3+}-doped Gd{sub 2}SiO{sub 5} single crystal with high optical quality has been grown by the Czochralski method. Polarized absorption and fluorescence spectra and fluorescence lifetime of the crystal were measured at room temperature. Intensity parameters, spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetimes were estimated on the basis of the Judd–Ofelt theory. Besides, potentiality of 1.55 μm laser emission in an Er{sup 3+}–Yb{sup 3+} co-doped Gd{sub 2}SiO{sub 5} crystal was evaluated.

  5. Amine free crystal structure: The crystal structure of d(CGCGCG)2 and methylamine complex crystal

    International Nuclear Information System (INIS)

    Ohishi, Hirofumi; Tsukamoto, Koji; Hiyama, Yoichi; Maezaki, Naoyoshi; Tanaka, Tetsuaki; Ishida, Toshimasa

    2006-01-01

    We succeeded in the crystallization of d(CGCGCG) 2 and methylamine Complex. The crystal was clear and of sufficient size to collect the X-ray crystallographic data up to 1.0 A resolution using synchrotron radiation. As a result of X-ray crystallographic analysis of 2F o - F c map was much clear and easily traced. It is First time monoamine co-crystallizes with d(CGCGCG) 2 . However, methylamine was not found from the complex crystal of d(CGCGCG) 2 and methylamine. Five Mg ions were found around d(CGCGCG) 2 molecules. These Mg ions neutralized the anion of 10 values of the phosphate group of DNA with five Mg 2+ . DNA stabilized only by a metallic ion and there is no example of analyzing the X-ray crystal structure like this. Mg ion stabilizes the conformation of Z-DNA. To use monoamine for crystallization of DNA, we found that we can get only d(CGCGCG) 2 and Mg cation crystal. Only Mg cation can stabilize the conformation of Z-DNA. The method of using the monoamine for the crystallization of DNA can be applied to the crystallization of DNA of long chain of length in the future like this

  6. Investigation of the thermoluminescent response of K2GdF5:Dy3+ crystals to photon radiation and neutron fields

    International Nuclear Information System (INIS)

    Silva, Edna C.; Faria, Luiz O.; Santos, Joelan A.L.; Vilela, Eudice C.

    2009-01-01

    The thermoluminescent (TL) properties of undoped and Dy 3+ doped K 2 GdF 5 crystals were investigated from the point of view of gamma and neutron dosimetry. Crystalline K 2 GdF 5 platelets with thickness of about 1 mm and doped with 0.0, 0.2, 1.0, 5.0 and 10.0 at.% Dy 3+ ions, synthesized under hydrothermal conditions, were irradiated in order to study TL sensitivity, as well as dose and energy response, reproducibility and fading. As it has been turned out, crystals doped with 5.0 at% Dy 3+ show the most efficient TL response and demonstrate a linear response to doses for all the radiation fields. TL glow curves from Dy 3+ doped K 2 GdF 5 crystals can be deconvoluted into four individual TL peaks centered at 153, 185, 216 and 234 deg C. Concerning the photon fields studied, the maximum TL response has been found for the 52.5 keV photons. The intensity is 15 times more than that of the response for the 662 keV photons from a Cs-137 source. On the other hand, the K 2 GdF 5 crystals doped with 5.0 at % Dy 3+ have also been found to have the better TL response for fast neutron radiation, among all dopants studied. For fast neutron radiation produced by a 241 Am-Be source, the TL responses for doses were also linear and comparable to that of commercial TLD-600, irradiated at same conditions. It has been established that the gamma sensitivity of the crystals is about 0.07% of the neutron sensitivity and the fast neutron sensitivity is about 4.5 % of the thermal neutron sensitivity. These results points out that K 2 Gd 0.95 Dy 0.05 F 5 crystals are good candidates for use in neutron dosimetry applications. (author)

  7. Synthesis and characterization of Gd-doped magnetite nanoparticles

    International Nuclear Information System (INIS)

    Zhang, Honghu; Malik, Vikash; Mallapragada, Surya; Akinc, Mufit

    2017-01-01

    Synthesis of magnetite nanoparticles has attracted increasing interest due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. Here we investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizes under the conditions tested (0–10 at% Gd"3"+). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. Our results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd"3"+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe_(_3_−_x_)Gd_xO_4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity (~65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method. - Highlights: • Gd-doped magnetite nanoparticles are synthesized via aqueous co-precipitation method under mild conditions. • Gd doping affects growth of magnetite nanoparticles leading to tunable particle size. • Gd-doped magnetite nanoparticles exhibit ferrimagnetic properties.

  8. Lanthanide-activated Na5Gd9F32 nanocrystals precipitated from a borosilicate glass: Phase-separation-controlled crystallization and optical property

    International Nuclear Information System (INIS)

    Chen, Daqin; Wan, Zhongyi; Zhou, Yang; Chen, Yan; Yu, Hua; Lu, Hongwei; Ji, Zhenguo; Huang, Ping

    2015-01-01

    Highlights: • Na 5 Gd 9 F 32 nanocrystals embedded glass ceramics were fabricated for the first time. • Such glass ceramics were achieved by phase-separation-controlled crystallization. • Elemental mapping evidenced the segregation of activators into the Na 5 Gd 9 F 32 lattice. • Luminescent color could be tuned by controlling glass crystallization temperature. - Abstract: Lanthanide-activated cubic Na 5 Gd 9 F 32 nanocrystals were precipitated from a borosilicate glass with a specifically designed composition. The precursor glass is already phase-separated after melt-quenching, which is beneficial to the realization of the controllable glass crystallization for affording desirable size, morphology and activator partition. Elemental mapping in the scanning transmission electron microscopy evidenced that the segregation of lanthanide ions into the Na 5 Gd 9 F 32 lattice was in situ formed without the requirement of long-range ionic diffusion. Impressively, such fabricated glass ceramic co-doped with Yb 3+ /Er 3+ ions exhibited intense upconversion luminescence, which was about 500 times higher than that of the precursor glass, and its luminescent color could be easily tuned from red to green by controlling glass crystallization temperature. It is anticipated that such phase-separation synthesis strategy with precise control over nanostructure of glass ceramics offer a great opportunity to design other highly transparent nanocomposites with a wide range of tunable optical properties

  9. Growth and characterization of Nd-doped disordered Ca3Gd2(BO3)4 crystal

    Science.gov (United States)

    Pan, Z. B.; Zhang, H. J.; Yu, H. H.; Xu, M.; Zhang, Y. Y.; Sun, S. Q.; Wang, J. Y.; Wang, Q.; Wei, Z. Y.; Zhang, Z. G.

    2012-01-01

    A high-quality disordered Nd3+:Ca3Gd2(BO3)4 (Nd3+:CGB) laser crystal was grown by the Czochralski method. The space group and effective segregation coefficient of Nd3+ were determined to be Pnma and 1.06, respectively. The thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were systematically measured for the first time. It was found that the thermal conductivity increases with increasing temperature, indicating glasslike behavior. The polarized spectral properties of the crystal were investigated, including the polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay. The spectroscopic parameters of Nd3+ ions in Nd3+:CGB crystal have been obtained based on Judd-Ofelt theory. The anisotropy of the spectral properties for different polarized directions was discussed. Additionally, the continuous-wave (CW) laser performance at 1.06 μm was demonstrated for the first time. The maximum output power of 603 mW was achieved with corresponding optical conversion efficiency of 8.33% and slope efficiency of 9.95%.

  10. Doping effects on the structural, magnetic, and hyperfine properties of Gd-doped SnO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Coelho-Júnior, H.; Aquino, J. C. R.; Aragón, F. H. [Universidade de Brasília, Núcleo de Física Aplicada, Instituto de Física (Brazil); Hidalgo, P. [Universidade de Brasília, Faculdade Gama-FGA, Setor Central Gama (Brazil); Cohen, R.; Nagamine, L. C. C. M. [Universidade de São Paulo, Instituto de Física (Brazil); Coaquira, J. A. H., E-mail: coaquira@unb.br; Silva, S. W. da [Universidade de Brasília, Núcleo de Física Aplicada, Instituto de Física (Brazil); Brito, H. F. [Universidade de São Paulo, Instituto de Química (Brazil)

    2014-12-15

    In this work we present the study of the structural, magnetic, and hyperfine properties of Gd-doped SnO{sub 2} nanoparticles synthesized by a polymer precursor method. The X-ray diffraction data analysis shows the formation of the rutile-type structure in all samples with Gd content from 1.0 to 10.0 mol%. The mean crystallite size is ∼11 nm for the 1.0 mol% Gd-doped samples and it shows a decreasing tendency as the Gd content is increased. The analysis of magnetic measurements indicates the coexistence of ferromagnetic and paramagnetic phases for the 1.0 mol% Gd-doped sample; however, above that content, only a paramagnetic phase is observed. The ferromagnetic phase observed in the 1.0 mol% Gd-doped sample has been assigned to the presence of bound magnetic polarons which overlap to create a spin-split impurity band. Room-temperature {sup 119}Sn Mössbauer measurements reveal the occurrence of strong electric quadrupole interactions. It has been determined that the absence of magnetic interactions even for 1.0 mol% Gd-doped sample has been related to the weak magnetic field associated to the exchange interaction between magnetic ions and the donor impurity band. The broad distribution of electric quadrupole interactions are attributed to the several non-equivalent surroundings of Sn{sup 4+} ions provoked by the entrance of Gd{sup 3+} ions and to the likely presence of Sn{sup 2+} ions. The isomer shift seems to be nearly independent of the Gd content for samples with Gd content below 7.5 mol%.

  11. Crystal structure study of new lanthanide silicates with silico-carnotite structure

    International Nuclear Information System (INIS)

    Piccinelli, F.; Lausi, A.; Speghini, A.; Bettinelli, M.

    2012-01-01

    The crystal structures of new rare earth-based silicate compounds (Ca 3 Eu 2 Si 3 O 12 , Ca 3 Gd 2 Si 3 O 12 , Ca 3 Dy 2 Si 3 O 12 , Ca 3 Er 2 Si 3 O 12 and Ca 3 Lu 2 Si 3 O 12 ) have been determined using powder X-ray diffraction. From Rietveld refinement calculations on the collected powder patterns we observe a different distribution of the rare earth ions on the three available crystal sites characterized by different coordination numbers, depending on the ionic radius of the rare earth ion. The reasons of the instability of the silico-carnotite structure for lanthanide ions larger than Eu 3+ have been deduced. In addition, in order to detect crystal phase transitions, the powder patterns of Ca 3 Eu 2 Si 3 O 12 and Ca 3 Sm 2 Si 3 O 12 samples have been collected as a function of the temperature (RT-1000 °C range), but no phase transitions have been observed. - Graphical abstract: Synchrotron X-ray diffraction allows us the accurate determination of the RE 3+ ions distribution on the three available crystal sites of the silico-carnotite structure. Highlights: ► The structure of the Ca 3 M 2 Si 3 O 12 (M=Eu, Gd, Dy, Er and Lu) was determined. ► Different distribution of RE 3+ ions on the three available crystal sites was observed. ► The instability of the silico-carnotite structure for RE=La→Sm was discussed.

  12. The Deuteron Spin-dependent Structure Function $g^{d}_1$ and its First Moment

    CERN Document Server

    Alexakhin, V.Yu.; Alexeev, G.D.; Alexeev, M.; Amoroso, A.; Balestra, F.; Ball, J.; Barth, J.; Baum, G.; Becker, M.; Bedfer, Y.; Bernet, C.; Bertini, R.; Bettinelli, M.; Birsa, R.; Bisplinghoff, J.; Bordalo, P.; Bradamante, F.; Bressan, A.; Brona, G.; Burtin, E.; Bussa, M.P.; Bytchkov, V.N.; Chapiro, A.; Cicuttin, A.; Colantoni, M.; Colavita, A.A.; Costa, S.; Crespo, M.L.; d'Hose, N.; Dalla Torre, S.; Das, S.; Dasgupta, S.S.; De Masi, R.; Dedek, N.; Demchenko, D.; Denisov, O.Yu.; Dhara, L.; Diaz, V.; Dinkelbach, A.M.; Donskov, S.V.; Dorofeev, V.A.; Doshita, N.; Duic, V.; Dunnweber, W.; Efremov, A.; Eversheim, P.D.; Eyrich, W.; Faessler, M.; Fauland, P.; Ferrero, A.; Ferrero, L.; Finger, M.; M. Finger jr.; Fischer, H.; Franz, J.; Friedrich, J.M.; Frolov, V.; Garfagnini, R.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Geyer, R.; Giorgi, M.; Gobbo, B.; Goertz, S.; Gorin, A.M.; Grajek, O.A.; Grasso, A.; Grube, B.; Guskov, A.; Haas, F.; Hannappel, J.; von Harrach, D.; Hasegawa, T.; Hedicke, S.; Heinsius, F.H.; Hermann, R.; Hess, C.; Hinterberger, F.; von Hodenberg, M.; Horikawa, N.; Horikawa, S.; Horn, I.; Ilgner, C.; Ioukaev, A.I.; Ivanchin, I.; Ivanov, O.; Iwata, T.; Jahn, R.; Janata, A.; Joosten, R.; Jouravlev, N.I.; Kabuss, E.; Kang, D.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koblitz, S.; Koivuniemi, J.H.; Kolosov, V.N.; Komissarov, E.V.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Korentchenko, A.S.; Korzenev, A.; Kotzinian, A.M.; Koutchinski, N.A.; Kouznetsov, O.; Kowalik, K.; Kramer, D.; Kravchuk, N.P.; Krivokhizhin, G.V.; Kroumchtein, Z.V.; Kubart, J.; Kuhn, R.; Kukhtin, V.; Kunne, F.; Kurek, K.; Ladygin, M.E.; Lamanna, M.; Le Goff, J.M.; Leberig, M.; Lednev, A.A.; Lehmann, A.; Lichtenstadt, J.; Liska, T.; Ludwig, I.; Maggiora, A.; Maggiora, M.; Magnon, A.; Mallot, G.K.; Marchand, C.; Marroncle, J.; Martin, A.; Marzec, J.; Masek, L.; Massmann, F.; Matsuda, T.; Matthia, D.; Maximov, A.N.; Meyer, W.; Mielech, A.; Mikhailov, Yu. V.; Moinester, M.A.; Nagel, T.; Nahle, O.; Nassalski, J.; Neliba, S.; Neyret, D.P.; Nikolaenko, V.I.; Nikolaev, K.; Nozdrin, A.A.; Obraztsov, V.F.; Olshevsky, A.G.; Ostrick, M.; Padee, A.; Pagano, P.; Panebianco, S.; Panzieri, D.; Paul, S.; Peshekhonov, D.V.; Peshekhonov, V.D.; Piragino, G.; Platchkov, S.; Pochodzalla, J.; Polak, J.; Polyakov, V.A.; Pontecorvo, G.; Popov, A.A.; Pretz, J.; Procureur, S.; Quintans, C.; Ramos, S.; Reicherz, G.; Rondio, E.; Rozhdestvensky, A.M.; Ryabchikov, D.; Samoylenko, V.D.; Sandacz, A.; Santos, H.; Sapozhnikov, M.G.; Savin, I.A.; Schiavon, P.; Schill, C.; Schmitt, L.; Schroeder, W.; Seeharsch, D.; Seimetz, M.; Setter, D.; Shevchenko, O.Yu.; Siebert, H.W.; Silva, L.; Sinha, L.; Sissakian, A.N.; Slunecka, M.; Smirnov, G.I.; Sozzi, F.; Srnka, A.; Stinzing, F.; Stolarski, M.; Sugonyaev, V.P.; Sulc, M.; Sulej, R.; Tchalishev, V.V.; Tessaro, S.; Tessarotto, F.; Teufel, A.; Tkatchev, L.G.; Trippel, S.; Venugopal, G.; Virius, M.; Vlassov, N.V.; Webb, R.; Weise, E.; Weitzel, Q.; Windmolders, R.; Wislicki, W.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Zhao, J.; Zvyagin, A.

    2007-01-01

    We present a measurement of the deuteron spin-dependent structure function g^d_1 based on the data collected by the COMPASS experiment at CERN during the years 2002-2004. The data provide an accurate evaluation for \\Gamma^d_1, the first moment of g^d_1(x), and for the matrix element of the singlet axial current, a_0. The results of QCD fits in the next to leading order (NLO) on all g1 deep inelastic scattering data are also presented. They provide two solutions with the gluon spin distribution function \\Delta_G positive or negative, which describe the data equally well. In both cases, at Q^2 = 3(GeV/c)^2 the first moment of \\Delta G is found to be of the order of 0:2 - 0:3 in absolute value.

  13. Positron annihilation study on the superconductivity of Gd-doped YBCO system

    International Nuclear Information System (INIS)

    Chen Zhenping; Su Yuling; Xue Yuncai; Liu Haizeng; Gong Shicheng; Zhao Jingxun; Li Xigui

    2006-01-01

    To make clear the influence of magnetic rare-earth ion Gd 3+ doping in the Y site on crystal structure and localized electron structure of YBCO system, the Gd-doped Y 1-x Gd x Ba 2 Cu 3 O 7-δ (x=0-1.0) systems were studied systematically by the positron annihilation technique and X-ray diffraction (XRD). The XRD analysis reveals that Gd 3+ with bigger radius doping in Y site makes the crystal parameters and crystal volume increase, while all the samples remain the single orthorhombic phase as YBa 2 Cu 3 O 7-δ (YBCO) system does. The temperature dependence of resistance measurement shows that T c is above 90 K for all samples, and T c increases with increasing Gd 3+ content. The positron experiment indicates that the localized electronic density n e decreases with increasing Gd 3+ content. (authors)

  14. Spectroscopic properties and laser performance at 1,066 nm of a new laser crystal Nd:GdTaO4

    Science.gov (United States)

    Peng, Fang; Yang, Huajun; Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Sun, Dunlu; Dou, Renqin; Sun, Guihua

    2015-03-01

    A new laser medium Nd3+:GdTaO4 single crystal with high optical quality was grown successfully by the Czochralski method, and its high-efficiency laser operation at 1,066 nm was demonstrated for the first time. The absorption cross section of the crystal at 808 nm is 5.098 × 10-20 cm2, and the full width at half maximum of this absorption band is about 6 nm. Spectral properties are investigated by Judd-Ofelt theory. The stimulated emission cross section at 1,066 nm is 3.9 × 10-19 cm2, and the fluorescence lifetime of 4F3/2 level is 178.4 μs. A diode end-pumped Nd:GdTaO4 laser at 1,066 nm with the maximum output power of 2.5 W is achieved in the continuous-wave mode. The optical-to-optical conversion efficiency and slope efficiency are 34.6 and 36 %, respectively. In addition, the fluorescence branching ratio of 4F3/2 → 4I9/2 transition reaches 44.4 %, indicating that Nd:GdTaO4 may be an efficient laser medium at 920 nm. All the results demonstrate that Nd:GdTaO4 crystal is a good candidate for laser diode-pumped laser material.

  15. Crystal structures and some physical properties of perovskite type vanadites of lanthanide-series elements

    Energy Technology Data Exchange (ETDEWEB)

    Shinike, T [Osaka Dental Coll., Hirakata (Japan); Adachi, G; Shiokawa, J

    1980-04-01

    Crystal structures and some physical properties of the perovskite type vanadites of the lanthanide-series elements were studied. LaVO/sub 3/ and CeVO/sub 3/ had a tetragonal unit cell and other compounds studied were isostructural with orthorhombic GdFeO/sub 3/. The conductivity of all compounds showed semiconductive behavior with an activation energy about 0.1 eV. Electrical conductivity at room temperature decreased along the series from LaVO/sub 3/ to GdVO/sub 3/, and quasiconstant values were observed from TbVO/sub 3/ to LuVO/sub 3/. All the compounds studied, with the exception of LaVO/sub 3/, SmVO/sub 3/ and GdVO/sub 3/, were antiferromagnets with a weak ferromagnetism because of antisymmetric exchange interaction at low temperatures. At high temperature, all the compounds showed paragnetism.

  16. Substitution studies of Mn and Fe in Ln{sub 6}W{sub 4}Al{sub 43} (Ln=Gd, Yb) and the structure of Yb{sub 6}Ti{sub 4}Al{sub 43}

    Energy Technology Data Exchange (ETDEWEB)

    Treadwell, LaRico J.; Watkins-Curry, Pilanda [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Department of Chemistry, University of Texas at Dallas, Richardson, TX 75080 (United States); McAlpin, Jacob D. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Prestigiacomo, Joseph; Stadler, Shane [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Chan, Julia Y., E-mail: Julia.Chan@utdallas.edu [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Department of Chemistry, University of Texas at Dallas, Richardson, TX 75080 (United States)

    2014-02-15

    The synthesis and characterization of Mn- and Fe-substituted Ln{sub 6}W{sub 4}Al{sub 43} (Ln=Gd, Yb) and Yb{sub 6}Ti{sub 4}Al{sub 43} are reported. The compounds adopt the Ho{sub 6}Mo{sub 4}Al{sub 43} structure type with lattice parameters of a∼11 Å and c∼17.8 Å with structural site preferences for Mn and Fe. The magnetization of Yb{sub 6}W{sub 4}Al{sub 43} is sensitive to Mn and Fe doping, which is evident by an increase in the field dependent magnetization. Gd{sub 6}W{sub 4}Al{sub 43}, Gd{sub 6}W{sub 4}Al{sub 42.31(11)}Mn{sub 0.69(11)}, and Gd{sub 6}W{sub 4}Al{sub 41.69(12)}Fe{sub 1.30(12)} order antiferromagnetically in the ab- and c-directions at 15, 14, and 13 K, respectively, with positive Weiss constants, suggesting the presence of ferromagnetic exchange interactions. Anisotropic magnetization data of Gd{sub 6}W{sub 4}Al{sub 43−y}T{sub y} (T=Mn, Fe) analogs are discussed. - Graphical abstract: The magnetic susceptibility of Ln{sub 6}W{sub 4−x}Al{sub 43−y}T{sub x+y} (Ln = Gd, Yb; T= Mn, Fe). Display Omitted - Highlights: • Single crystals of Ln{sub 6}W{sub 4−x}Al{sub 43−y}T{sub x+y} were grown with Al-flux. • Anisotropic magnetic behavior were determined on single crystals. • Gd{sub 6}W{sub 4−x}Al{sub 43−y}T{sub x+y} (T=Mn, Fe) analogs order antiferromagnetically.

  17. Study of effect of quenching and deformation on KCl: Gd crystals by ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The study of ionic conductivity vs reciprocal temperature of pure KCl and KCl crystal doped with. 0⋅1, 0⋅3 and 0⋅5 mole% gadolinium has been carried out in as grown, quenched from elevated temperatures. (100, 350 and 500°C) and annealed at various timings i.e. 2–3 h and deformed by different percentages.

  18. Phase equilibria and crystal chemistry of the CaO-½Gd2O3-CoOz system at 885 °C in air

    Science.gov (United States)

    Wong-Ng, W.; Laws, W.; Lapidus, S. H.; Ribaud, L.; Kaduk, J. A.

    2017-10-01

    The CaO-½Gd2O3-CoOz system prepared at 885 °C in air consists of two thermoelectric calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xGdx)Co4O9-z (0 ≤ x ≤ 0.42) which has a misfit layered structure, and the 1D Ca3Co2O6 compound which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound. In the peripheral binary systems, Gd was not present in the Ca site of CaO, while a small solid solution region was identified for (Gd1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.075). A solid solution region of distorted perovskite, (Gd1-xCax)CoO3-z (0 ≤ x ≤ 0.24, space group Pnma) was established. The structure of a member of the solid solution, (Gd0.92Ca0.08)CoO3-z, was determined using high resolution synchrotron radiation. A ternary oxide compound CaGdCoO4-z which has an orthorhombic structure (Bmab) was found to be stable at this temperature. Five solid solution tie-line regions and six three-phase regions were determined in the CaO-½Gd2O3-CoOz system. A comparison of the phase diagrams of the CaO-½R2O3-CoOz (R = La, Sm and Gd) systems is provided.

  19. Synthesis, structure and photoluminescence of novel lanthanide (Tb(III), Gd(III)) complexes with 6-diphenylamine carbonyl 2-pyridine carboxylate

    International Nuclear Information System (INIS)

    An Baoli; Gong Menglian; Cheah, Kok-Wai; Wong, Wai-Kwok; Zhang Jiming

    2004-01-01

    A novel organic ligand, 6-diphenylamine carbonyl 2-pyridine carboxylic acid (HDPAP), and the corresponding lanthanide complexes, tris(6-diphenylamine carbonyl 2-pyridine carboxylato) terbium(III) (Tb-DPAP) and tris(6-diphenylamine carbonyl 2-pyridine carboxylato) gadolinium(III) (Gd-DPAP) have been designed and synthesized. The crystal structure and photoluminescence of Tb-DPAP and Gd-DPAP have been studied. The results showed that the lanthanide complexes have electroneutral structures, and the solid terbium complex emits characteristic green fluorescence of Tb(III) ions at room temperature while the gadolinium complex emits the DPAP ligand phosphorescence. The lowest triplet level of DPAP ligand was calculated from the phosphorescence spectrum of Gd-DPAP in N,N-dimethyl formamide (DMF) dilute solution determined at 77 K, and the energy transfer mechanisms in the lanthanide complexes were discussed. The lifetimes of the 5 D 4 levels of Tb 3+ ions in the terbium complex were examined using time-resolved spectroscopy, and the values are 0.0153±0.0001 ms for solid Tb(DPAP) 3 ·11.5H 2 O and 0.074±0.007 ms for 2.5x10 -5 mol/l Tb-DPAP ethanol solution

  20. Structural and optical properties of Tb-doped Na-Gd metaphosphate glasses and glass-ceramics

    Czech Academy of Sciences Publication Activity Database

    Moretti, F.; Vedda, A.; Nikl, Martin; Nitsch, Karel

    2009-01-01

    Roč. 21, č. 15 (2009), 155103/1-155103/7 ISSN 0953-8984 R&D Projects: GA AV ČR IAA200100626 Institutional research plan: CEZ:AV0Z10100521 Keywords : Na-Gd metaphosphate glass * glass -ceramics * NaGd(PO 3 ) 4 * optical properties * structural properties * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.964, year: 2009

  1. What makes a crystal structure report valid?

    NARCIS (Netherlands)

    Spek, Anthony L.|info:eu-repo/dai/nl/156517566

    2018-01-01

    Single crystal X-ray crystallography has developed into a unique, highly automated and accessible tool to obtain detailed information on molecular structures. Proper archival makes that referees, readers and users of the results of reported crystal structures no longer need to depend solely on the

  2. Crystal structure of prethrombin-1

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhiwei; Pelc, Leslie A.; Di Cera, Enrico (St. Louis-MED)

    2010-11-15

    Prothrombin is the zymogen precursor of the clotting enzyme thrombin, which is generated by two sequential cleavages at R271 and R320 by the prothrombinase complex. The structure of prothrombin is currently unknown. Prethrombin-1 differs from prothrombin for the absence of 155 residues in the N-terminal domain and is composed of a single polypeptide chain containing fragment 2 (residues 156-271), A chain (residues 272-320), and B chain (residues 321-579). The X-ray crystal structure of prethrombin-1 solved at 2.2-{angstrom} resolution shows an overall conformation significantly different (rmsd = 3.6 {angstrom}) from that of its active form meizothrombin desF1 carrying a cleavage at R320. Fragment 2 is rotated around the y axis by 29{sup o} and makes only few contacts with the B chain. In the B chain, the oxyanion hole is disrupted due to absence of the I16-D194 ion pair and the Na{sup +} binding site and adjacent primary specificity pocket are highly perturbed. A remarkable feature of the structure is that the autolysis loop assumes a helical conformation enabling W148 and W215, located 17 {angstrom} apart in meizothrombin desF1, to come within 3.3 {angstrom} of each other and completely occlude access to the active site. These findings suggest that the zymogen form of thrombin possesses conformational plasticity comparable to that of the mature enzyme and have significant implications for the mechanism of prothrombin activation and the zymogen {yields} protease conversion in trypsin-like proteases.

  3. Luminescence properties and gamma-ray response of the Ce and Ca co-doped (Gd,Y)F{sub 3} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kamada, Kei, E-mail: k-kamada@furukawakk.co.jp [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai (Japan); Furukawa Co. Ltd. (Japan); Yanagida, Takayuki; Fujimoto, Yutaka; Fukabori, Akihiro [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai (Japan); Yoshikawa, Akira [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai (Japan); New Industry Creation Hatchery Center, Tohoku University, Sendai (Japan); Nikl, Martin [Institute of Physics AS CR (Czech Republic)

    2011-12-11

    The Ca0.5% and Ce1%, 3%, 7%, 10% co-doped Gd{sub 0.5}Y{sub 0.5}F{sub 3} single crystals were grown by the {mu}-PD method. In the Ca0.5% and Ce3% co-doped sample, Ce{sup 3+}-perturbed luminescence at 380 nm was observed with 32.4 ns photoluminescence decay time. The energy transfer in the sequence of the regular Ce{sup 3+}{yields} (Gd{sup 3+}){sub n}{yields} the perturbed Ce{sup 3+} sites was evidenced through observation of decay time shortening of the regular Ce{sup 3+} and Gd{sup 3+} centers and the change between the Gd{sup 3+} and Ce{sup 3+}-perturbed emission intensity. The gamma-ray excited scintillation response of the Ca0.5%, Ce7% co-doped Gd{sub 0.5}Y{sub 0.5}F{sub 3} sample was investigated with the help of the pulse height spectra and the light yield, energy resolution and non-proportionality was evaluated in the interval of energies of 59.4-1274 keV.

  4. Luminescence properties and gamma-ray response of the Ce and Ca co-doped (Gd,Y)F3 single crystals

    International Nuclear Information System (INIS)

    Kamada, Kei; Yanagida, Takayuki; Fujimoto, Yutaka; Fukabori, Akihiro; Yoshikawa, Akira; Nikl, Martin

    2011-01-01

    The Ca0.5% and Ce1%, 3%, 7%, 10% co-doped Gd 0.5 Y 0.5 F 3 single crystals were grown by the μ-PD method. In the Ca0.5% and Ce3% co-doped sample, Ce 3+ -perturbed luminescence at 380 nm was observed with 32.4 ns photoluminescence decay time. The energy transfer in the sequence of the regular Ce 3+ → (Gd 3+ ) n → the perturbed Ce 3+ sites was evidenced through observation of decay time shortening of the regular Ce 3+ and Gd 3+ centers and the change between the Gd 3+ and Ce 3+ -perturbed emission intensity. The gamma-ray excited scintillation response of the Ca0.5%, Ce7% co-doped Gd 0.5 Y 0.5 F 3 sample was investigated with the help of the pulse height spectra and the light yield, energy resolution and non-proportionality was evaluated in the interval of energies of 59.4-1274 keV.

  5. GdCuMg with ZrNiAl-type structure. An 82.2 K ferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Sebastian; Heletta, Lukas; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2017-08-01

    GdCuMg has been synthesized by induction-melting of the elements in a sealed niobium ampoule followed by annealing in a muffle furnace. The sample was studied by powder and single crystal X-ray diffraction: ZrNiAl type, P anti 62m (a=749.2(4), c=403.3(1) pm), wR2=0.0242, 315 F{sup 2} values and 15 variables. Temperature dependent magnetic susceptibility measurements have revealed an experimental magnetic moment of 8.54(1) μ{sub B} per Gd atom. GdCuMg orders ferromagnetically below T{sub C}=82.2(5) K and based on the magnetization isotherms it can be classified as a soft ferromagnet.

  6. Crystal structure of 2-pentyloxybenzamide

    Directory of Open Access Journals (Sweden)

    Bernhard Bugenhagen

    2014-10-01

    Full Text Available In the title molecule, C12H17NO2, the amide NH2 group is oriented toward the pentyloxy substituent and an intramolecular N—H...O hydrogen bond is formed with the pentyloxy O atom. The benzene ring forms dihedral angles of 2.93 (2 and 5.60 (2° with the amide group and the pentyloxy group mean planes, respectively. In the crystal, molecules are linked by pairs of N—H...O hydrogen bonds, forming inversion dimers with their molecular planes parallel, but at an offset of 0.45 (1 Å to each other. These dimers are ordered into two types of symmetry-related columns extended along the a axis, with the mean plane of one set of dimers in a column approximately parallel to (121 and the other in a column approximately parallel to (1-21. The two planes form a dihedral angle of 85.31 (2°, and are linked via C—H...O hydrogen bonds and C—H...π interactions, forming a three-dimensional framework structure.

  7. Method of fabricating patterned crystal structures

    KAUST Repository

    Yu, Liyang

    2016-12-15

    A method of manufacturing a patterned crystal structure for includes depositing an amorphous material. The amorphous material is modified such that a first portion of the amorphous thin-film layer has a first height/volume and a second portion of the amorphous thin-film layer has a second height/volume greater than the first portion. The amorphous material is annealed to induce crystallization, wherein crystallization is induced in the second portion first due to the greater height/volume of the second portion relative to the first portion to form patterned crystal structures.

  8. Density functional studies on the exchange interaction of a dinuclear Gd(iii)-Cu(ii) complex: method assessment, magnetic coupling mechanism and magneto-structural correlations.

    Science.gov (United States)

    Rajaraman, Gopalan; Totti, Federico; Bencini, Alessandro; Caneschi, Andrea; Sessoli, Roberta; Gatteschi, Dante

    2009-05-07

    Density functional calculations have been performed on a [Gd(iii)Cu(ii)] complex [L(1)CuGd(O(2)CCF(3))(3)(C(2)H(5)OH)(2)] () (where L(1) is N,N'-bis(3-ethoxy-salicylidene)-1,2-diamino-2-methylpropanato) with an aim of assessing a suitable functional within the DFT formalism to understand the mechanism of magnetic coupling and also to develop magneto-structural correlations. Encouraging results have been obtained in our studies where the application of B3LYP on the crystal structure of yields a ferromagnetic J value of -5.8 cm(-1) which is in excellent agreement with the experimental value of -4.42 cm(-1) (H = JS(Gd).S(Cu)). After testing varieties of functional for the method assessment we recommend the use of B3LYP with a combination of an effective core potential basis set. For all electron basis sets the relativistic effects should be incorporated either via the Douglas-Kroll-Hess (DKH) or zeroth-order regular approximation (ZORA) methods. A breakdown approach has been adopted where the calculations on several model complexes of have been performed. Their wave functions have been analysed thereafter (MO and NBO analysis) in order to gain some insight into the coupling mechanism. The results suggest, unambiguously, that the empty Gd(iii) 5d orbitals have a prominent role on the magnetic coupling. These 5d orbitals gain partial occupancy via Cu(ii) charge transfer as well as from the Gd(iii) 4f orbitals. A competing 4f-3d interaction associated with the symmetry of the complex has also been observed. The general mechanism hence incorporates both contributions and sets forth rather a prevailing mechanism for the 3d-4f coupling. The magneto-structural correlations reveal that there is no unique parameter which the J values are strongly correlated with, but an exponential relation to the J value found for the O-Cu-O-Gd dihedral angle parameter is the most credible correlation.

  9. Structure and magnetic properties of Gd{sub x}Y{sub 1−x}FeO{sub 3} obtained by mechanosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Bolarín-Miró, A.M. [Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo Mineral de la Reforma, Hidalgo 42184 (Mexico); Sánchez-De Jesús, F., E-mail: fsanchez@uaeh.edu.mx [Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo Mineral de la Reforma, Hidalgo 42184 (Mexico); Cortés-Escobedo, C.A. [Centro de Investigación e Innovación Tecnológica del IPN, Distrito Federal 02250 (Mexico); Valenzuela, R. [Depto. de Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Ammar, S. [ITODYS, UMR 7086, Université de Paris-Diderot, 75250 Paris Cedex (France)

    2014-02-15

    Highlights: • Orthohombic GDxY1-xFeO3 was obtained by mechanosynthesis after 5 h of milling. • Mechanosynthesized GdxY1-xFeO3 show weak ferromagnetic behavior. • Mechanosynthesis promotes unexpected magnetic properties in GdxY1-xFeO3. • The maximum magnetization that was reached 7.7 emu/g for Gdo.75Y0.25FeO3. • For Gd0.5Y0.5FeO3, the magnetization decreases down to 2.1 emu/g. -- Abstract: Solid solutions of yttrium–gadolinium orthoferrites Gd{sub x}Y{sub 1−x}FeO{sub 3} (0 ⩽ x ⩽ 1) were prepared by high-energy ball milling. The aim of this work was to study the influence of the synthesis parameters on the crystal structure and the magnetic behavior of these solid solutions. The precursors, Fe{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and Gd{sub 2}O{sub 3}, mixed in a stoichiometric ratio to obtain these orthoferrites, were milled for different times (up to 5 h). X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the milling time. Results showed the complete formation of orthoferrite with an orthorhombic structure (S.G. Pbnm) without any annealing after 5 h of milling for all of the compositions. The effect of the synthesis process and the x value on the crystal structure and the magnetic properties were also studied. All of the synthesized powders demonstrated weak ferromagnetic behavior. In particular, an increase in the maximum magnetization for all the compositions was found, with a maximum that reached 7.7 emu/g for Gd{sub 0.75}Y{sub 0.25}FeO{sub 3}. For Gd{sub 0.5}Y{sub 0.5}FeO{sub 3}, the magnetization decreases down to 2.1 emu/g. A small contamination of metallic Fe was confirmed through electron spin resonance experiments.

  10. Probing ultrafast dynamics in electronic structure of epitaxial Gd(0 0 0 1) on W(1 1 0)

    Energy Technology Data Exchange (ETDEWEB)

    Beaulieu, Nathan [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette Cedex (France); Malinowski, Gregory [Laboratoire de Physique des Solides, Université Paris Sud, Orsay (France); Bendounan, Azzedine; Silly, Mathieu G.; Chauvet, Christian [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette Cedex (France); Krizmancic, Damjan [Instituto Officina dei Materiali (IOM)-CNR Laboratorio TASC, in Area Science Park S.S.14, Km 163.5, I-34149 Trieste (Italy); Sirotti, Fausto [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette Cedex (France)

    2013-08-15

    Highlights: •Study of the magnetism of epitaxial Gd(0 0 0 1)/W(1 1 0). •Study of Gd(0 0 0 1) band structure as a function of the temperature. •Study of the Gd magnetism dynamics probing the M5 edge. -- Abstract: The electronic and magnetic properties of Gd have been studied using time- and angle-resolved photoelectron spectroscopy employing laser pump and synchrotron radiation probe pulses. The static temperature evolution of the valence band and more precisely, the 5d6s exchange splitting is reported. Ultrafast demagnetization is measured using dichroic resonant Auger spectroscopy. Remarkably, a complete demagnetization is observed followed up by a non-monotonic recovery that could be associated to magnetization oscillations.

  11. Crystal growth, defects, and mechanical and spectral properties of a novel mixed laser crystal Nd:GdYNbO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Shoujun; Dou, Renqin [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China); University of Science and Technology of China, Hefei (China); Liu, Wenpeng; Zhang, Qingli; Peng, Fang; Luo, Jianqiao; Sun, Guihua; Sun, Dunlu [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China)

    2017-01-15

    A mixed laser crystal of Nd-doped GYNO crystal was grown successfully by Czochralski method. The crystal belongs to monoclinic system with space group I2/a, the structural parameters are obtained by the X-ray Rietveld refinement method. The defects and dislocations along three crystallographic orientations were studied by using the chemical etching method with the phosphoric acid etchant. The mechanical properties (including hardness, yield strength, fracture toughness, and brittle index) of the crystal were estimated by Vickers hardness test. The transmission spectrum was measured at room temperature, and the absorption peaks were assigned. Spectral properties of the as-grown crystal were investigated by Judd-Ofelt theory, and the Judd-Ofelt intense parameters Ω{sub 2,4,6} were obtained to be 9.674 x 10{sup -20}, 2.092 x 10{sup -20}, and 4.061 x 10{sup -20} cm{sup 2}, respectively. (orig.)

  12. Photonic Crystal Laser-Driven Accelerator Structures

    International Nuclear Information System (INIS)

    Cowan, B

    2004-01-01

    The authors discuss simulated photonic crystal structure designs for laser-driven particle acceleration. They focus on three-dimensional planar structures based on the so-called ''woodpile'' lattice, demonstrating guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice. They introduce a candidate geometry and discuss the properties of the accelerating mode. They also discuss the linear beam dynamics in the structure present a novelmethod for focusing the beam. In addition they describe ongoing investigations of photonic crystal fiber-based structures

  13. Data of evolutionary structure change: 1RAAA-3GD5C [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1RAAA-3GD5C 1RAA 3GD5 A C ANPLYQKHIISINDLSRDDLNLVLATAAKLKANPQPELL...LRDPFEAARGAHILYTDVWTHRLQLFEQYQINAALLN--------------CAAAEAIVLHCLPAHRGEEITDEVMEGPRS... 0 1RAA A 1RAAAA 1RAAA PLPRV--DEIAT...Chain> 1RAA A 1RAAA

  14. Data of evolutionary structure change: 1RAAA-3GD5D [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1RAAA-3GD5D 1RAA 3GD5 A D ANPLYQKHIISINDLSRDDLNLVLATAAKLKANPQPELL...RDPFEAARGAHILYTDVWTHRLQLFEQYQINAAL-----------LNC--AAAEAIVLHCLPAHRGEEITDEVMEGPRSRI... 0 1RAA A 1RAAA...RAA A 1RAAA P...ine> 1RAA A 1RAAA

  15. Passivation of the surfaces of single crystal gadolinium molybdate (Gd2(MoO4)3) against attack by hydrofluoric acid by inert ion beam irradiation

    International Nuclear Information System (INIS)

    Bhalla, A.; Cross, L.E.; Tongson, L.

    1978-01-01

    The passivation effect from inert ion beam bombardment has been studied on a ferroelectric surface. The mechanism in these materials may have some additional contributions because of the polarization charges of the domains and the dipole effect (ion beam and surface species) on the surfaces. For these studies Gd 2 (MoO 4 ) 3 (GMO) crystals were selected. Two possible mechanisms of passivation of GMO surfaces when bombarded with ion beams are discussed

  16. Effect of Al{sub 2}Gd on microstructure and properties of laser clad Mg–Al–Gd coatings

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hong; Zhang, Ke; Yao, Chengwu [Shanghai Key Lab of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Dong, Jie [National Engineering Research Center of Light Alloy Net Forming, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, Zhuguo, E-mail: lizg@sjtu.edu.cn [Shanghai Key Lab of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Emmelmann, Claus [Institute of Laser and System Technologies, Hamburg University of Technology, Hamburg, 21073 (Germany)

    2015-03-01

    Highlights: • Mg–Al–Gd coatings with different Gd contents were fabricated by fiber laser cladding. • Chemical compositions and crystal structures of the second phases were characterized. • Dispersion of Al{sub 2}Gd led to further grain refining and elevated mechanical properties. • Al{sub 2}Gd improved high-temperature performances by preventing tiny liquation. - Abstract: In order to investigate the effects of Gd addition on the microstructures and properties of magnesium coatings, the Mg–7.5Al–xGd (x = 0, 2.5, 5.0 and 7.5 wt.%) coatings on cast magnesium alloy were fabricated by laser cladding with wire feeding. The results indicated that the gadolinium (Gd) addition led to the formation of a cubic Al{sub 2}Gd phase as well as suppressed the precipitation of eutectic Mg{sub 17}Al{sub 12} phase. The laser clad coating containing nominally 7.5 wt.% Gd presented the highest microhardness, ultimate tensile strength and yield strength at both room temperature and high temperatures. The enhancement of heat resistant capacities was chiefly attributed to the existence of thermally stable Al{sub 2}Gd particles, which prevented tiny liquation of eutectic phases along the grain boundaries and made great contributions on maintaining high yield ratio during high-temperature deformation.

  17. Effect of Al2Gd on microstructure and properties of laser clad Mg–Al–Gd coatings

    International Nuclear Information System (INIS)

    Chen, Hong; Zhang, Ke; Yao, Chengwu; Dong, Jie; Li, Zhuguo; Emmelmann, Claus

    2015-01-01

    Highlights: • Mg–Al–Gd coatings with different Gd contents were fabricated by fiber laser cladding. • Chemical compositions and crystal structures of the second phases were characterized. • Dispersion of Al 2 Gd led to further grain refining and elevated mechanical properties. • Al 2 Gd improved high-temperature performances by preventing tiny liquation. - Abstract: In order to investigate the effects of Gd addition on the microstructures and properties of magnesium coatings, the Mg–7.5Al–xGd (x = 0, 2.5, 5.0 and 7.5 wt.%) coatings on cast magnesium alloy were fabricated by laser cladding with wire feeding. The results indicated that the gadolinium (Gd) addition led to the formation of a cubic Al 2 Gd phase as well as suppressed the precipitation of eutectic Mg 17 Al 12 phase. The laser clad coating containing nominally 7.5 wt.% Gd presented the highest microhardness, ultimate tensile strength and yield strength at both room temperature and high temperatures. The enhancement of heat resistant capacities was chiefly attributed to the existence of thermally stable Al 2 Gd particles, which prevented tiny liquation of eutectic phases along the grain boundaries and made great contributions on maintaining high yield ratio during high-temperature deformation

  18. Detection of pH and Enzyme-Free H2O2 Sensing Mechanism by Using GdO x Membrane in Electrolyte-Insulator-Semiconductor Structure.

    Science.gov (United States)

    Kumar, Pankaj; Maikap, Siddheswar; Qiu, Jian-Tai; Jana, Surajit; Roy, Anisha; Singh, Kanishk; Cheng, Hsin-Ming; Chang, Mu-Tung; Mahapatra, Rajat; Chiu, Hsien-Chin; Yang, Jer-Ren

    2016-12-01

    A 15-nm-thick GdO x membrane in an electrolyte-insulator-semiconductor (EIS) structure shows a higher pH sensitivity of 54.2 mV/pH and enzyme-free hydrogen peroxide (H2O2) detection than those of the bare SiO2 and 3-nm-thick GdO x membranes for the first time. Polycrystalline grain and higher Gd content of the thicker GdO x films are confirmed by transmission electron microscopy (TEM) and X-ray photo-electron spectroscopy (XPS), respectively. In a thicker GdO x membrane, polycrystalline grain has lower energy gap and Gd(2+) oxidation states lead to change Gd(3+) states in the presence of H2O2, which are confirmed by electron energy loss spectroscopy (EELS). The oxidation/reduction (redox) properties of thicker GdO x membrane with higher Gd content are responsible for detecting H2O2 whereas both bare SiO2 and thinner GdO x membranes do not show sensing. A low detection limit of 1 μM is obtained due to strong catalytic activity of Gd. The reference voltage shift increases with increase of the H2O2 concentration from 1 to 200 μM owing to more generation of Gd(3+) ions, and the H2O2 sensing mechanism has been explained as well.

  19. CW and AO Q-switched operation of a dual-crystal Tm, Ho:GdVO4 laser pumped by two diodes

    International Nuclear Information System (INIS)

    Li, L J; Bai, Y F; Liu, Y W; He, Z L; Wang, J; Yao, B Q; Zhou, S; Xing, M N

    2013-01-01

    Continuous wave (CW) mode and acousto-optic (AO) Q-switched mode operation of a dual-crystal Tm, Ho:GdVO 4 laser is reported. The dual-crystal Tm, Ho:GdVO 4 laser with output wavelength of 2.05 μm was pumped by two laser diodes (LDs). The Tm, Ho:GdVO 4 crystals were cooled by liquid nitrogen and pumped by two fiber-coupled LDs with a center output wavelength of 801.0 nm. A 20.5 W output power was obtained at a 255 mm physical cavity length in CW mode operation, and a 19.6 W average power was obtained at a pulse repetition frequency (PRF) of 10 kHz with a 19 ns pulse duration. Also, the efficiency loss of the laser is not more than 4.4% from CW mode to Q-switch mode, and the M 2 factor, which is measured by the traveling knife-edge method, does not exceed 1.2. (paper)

  20. Luminescent and laser properties of Yb Er:GdCa4O(BO3)3: a new crystal for eye-safe 1.5-μm lasers

    Science.gov (United States)

    Denker, B.; Galagan, B.; Ivleva, L.; Osiko, V.; Sverchkov, S.; Voronina, I.; Hellstrom, J. E.; Karlsson, G.; Laurell, F.

    2004-09-01

    We present for the first time 1.5-μm laser emission in Yb Er:GdCa4O(BO3)3 (GdCOB). The crystals were grown by the Czochralski method from platinum crucibles. Spectroscopic and laser tests of the crystals are described. A continuous-wave output power of 80 mW was achieved in a monolithic microchip cavity under laser-diode pumping.

  1. Enhanced flux pinning by BaZrO3 and (Gd,y)2O3 nano-structures in metal organic chemical vapor deposited GdYBCO high temperature superconductor tapes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Paranthaman, Mariappan Parans [ORNL; Cantoni, Claudia [ORNL; Aytug, Tolga [ORNL; Goyal, Amit [ORNL; Lee, Dominic F [ORNL; Specht, Eliot D [ORNL; Zuev, Yuri L [ORNL; Zhang, Yifei [ORNL

    2009-01-01

    We have formed BaZrO3 nano-columns and (Gd,Y)2O3 nano-precipitates in reel-to-reel MOCVD processed (Gd,Y)Ba2Cu3O7-x coated conductors and increased the critical currents (Ic) of the conductors in applied magnetic fields to remarkable levels. A (Gd,Y)Ba2Cu3O7-x tape of 1m length with 6.5% Zr-additions and 30% composition rich in both Gd and Y showed Ic values of 813 A/cm-width at (self-field, 77K) and above 186 A/cm-width at (1T, 77K). The strongly enhanced flux pinning over a wide range of magnetic field orientations can be attributed to the bidirectionally aligned defect structures of BaZrO3 and (Gd,Y)2O3 created by optimized MOCVD conditions.

  2. Hydrothermal synthesis, crystal structure and luminescence property ...

    Indian Academy of Sciences (India)

    The design and construction of ... dination polymers. It is difficult to design coordination .... The first endotherm at about 180 ... graphic data for coordination polymer 1. ... Sheldrick G M 1997 SHELXS-97: Program for solution of crystal structures ...

  3. imide, crystal structure, thermal and dielectric studies

    Indian Academy of Sciences (India)

    methyl imidazolium methylidene bis(trifluoromethanesulfonyl)imide, crystal structure, thermal and dielectric studies. BOUMEDIENE HADDAD1,2,3,∗, TAQIYEDDINE MOUMENE2, DIDIER VILLEMIN1,. JEAN-FRANÇOIS LOHIER1 and EL-HABIB ...

  4. SYNTHESIS, CRYSTAL STRUCTURE AND MAGNETIC ...

    African Journals Online (AJOL)

    Preferred Customer

    Much of the current effort on such extended hybrid metal organic complexes is ... In this paper, we report the synthesis, single crystal X-ray diffraction analysis and ..... with g = 2.0 (0.37 cm3 mol−1 K), and smoothly increases to a value of 0.45 ...

  5. Exploration of R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd2AlGe2 and Analysis of the U3Si2 and Zr3Al2 Structure Types

    Energy Technology Data Exchange (ETDEWEB)

    McWhorter, Sean William [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd5(SixGe1-x)4 several new compounds were synthesized with different crystal structures, but similar structural features. In Gd5(SixGe1-x)4, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd5(SixGe1-x)4 can be thought of as being formed from two 32434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd2MgGe2 and Gd2InGe2 both possess the same 32434 nets of Gd atoms as Gd5(SixGe1-x)4, but these nets are connected differently, forming the Mo2FeB2 crystal structure. A search of the literature revealed that compounds with the composition R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo2FeB2, Zr3Al2, Mn2AlB2 and W2CoB2 crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd2AlGe2 forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how

  6. Effect of Gd"3"+ substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe_2O_4

    International Nuclear Information System (INIS)

    Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Kumar, Arun; Singh, Mahavir

    2017-01-01

    Nanoparticles of CoGd_xFe_2_−_xO_4 with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd"3"+ substitution effect on different properties of nanocrystalline CoFe_2O_4 has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd"3"+ ions occupy the octahedral site in CoFe_2O_4. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd"3"+ substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd"3"+ substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd"3"+ substitution for Fe"3"+ at the octahedral sites. Low dielectric loss suggested the applicability of Gd"3"+ doped CoFe_2O_4 nanoparticles for high frequency microwave device applications. - Highlights: • Gd"3"+ ions were successfully added in to the spinel lattice of CoFe_2O_4. • Magnetic hysteresis loss is influenced by Gd"3"+ doping. • All doped samples exhibit normal dielectric dispersion behaviour of spinel ferrites. • UV–vis diffuse spectroscopy concludes band gap is reduced by Gd"3"+ doping.

  7. Effect of Mg$^{2+}$ ions co-doping on timing performance and radiation tolerance of Cerium doped Gd$_{3}$Al$_{2}$Ga$_{3}$O$_{12}$ crystals

    CERN Document Server

    Lucchini, M.T.; Bohacek, P.; Gundacker, S.; Kamada, K.; Nikl, M.; Petrosyan, A.; Yoshikawa, A.; Auffray, E.

    2016-01-01

    Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd3Al2Ga3O12 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd3Al2Ga3O12 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd3Al2Ga3O12 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233 ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments.

  8. Effect of Mg"2"+ ions co-doping on timing performance and radiation tolerance of Cerium doped Gd_3Al_2Ga_3O_1_2 crystals

    International Nuclear Information System (INIS)

    Lucchini, M.T.; Babin, V.; Bohacek, P.; Gundacker, S.; Kamada, K.; Nikl, M.; Petrosyan, A.; Yoshikawa, A.; Auffray, E.

    2016-01-01

    Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd_3Al_2Ga_3O_1_2 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd_3Al_2Ga_3O_1_2 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd_3Al_2Ga_3O_1_2 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233 ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments.

  9. Structural transition in lanthanum gallate and transformation of the fine structure of the EPR spectrum of a Gd3+ impurity center

    Science.gov (United States)

    Vazhenin, V. A.; Guseva, V. B.; Fokin, A. V.; Potapov, A. P.; Artyomov, M. Yu.

    2011-04-01

    Abrupt changes in resonance positions, hysteretic temperature behavior, and coexistence of phases, which indicate a first-order phase transition, have been revealed from measurements of temperature dependences of the EPR spectra of Gd3+ and Mn4+ centers in the vicinity of the structural transition of lanthanum gallate. The transformation of monoclinic Gd3+ centers into trigonal Gd3+ centers upon the phase transition has been used to estimate the adequacy of two approximations of the superposition model for parameters of the zero-field splitting of the ground state.

  10. Thermal, Spectral and Laser Properties of Er3+:Yb3+:GdMgB₅O10: A New Crystal for 1.5 μm Lasers.

    Science.gov (United States)

    Huang, Yisheng; Yuan, Feifei; Sun, Shijia; Lin, Zhoubin; Zhang, Lizhen

    2017-12-25

    A novel laser crystal of Er 3+ :Yb 3+ :GdMgB₅O 10 with dimension of 26 × 16 × 12 mm³ was grown successfully from K₂Mo₃O 10 flux by the top seeded solution growth method. The thermal diffusivity and specific heat capacity were measured to calculate the thermal conductivity of the crystal. The absorption and fluorescence properties of the crystal at room temperature were investigated in detail. The Judd-Ofelt method was used to analyze the polarized absorption spectra. The emission cross-section of the ⁴I 13/2 →⁴I 15/2 transition was calculated by the Füchtbauer-Ladenburg formula and the relevant gain cross-sections were estimated. Continuous-wave laser output of 140 mW at 1569 nm with the slope efficiency of 17.8% was demonstrated in a plano-concave resonator. The results reveal that Er 3+ :Yb 3+ :GdMgB₅O 10 crystal is a promising material for 1.5 μm lasers.

  11. Crystal structure from one-electron theory

    DEFF Research Database (Denmark)

    Skriver, H. L.

    1985-01-01

    The authors have studied the crystal structure of all the 3d, 4d, and 5d transition metals at zero pressure and temperature by means of the linear muffin-tin orbital method and Andersen's force theorem. They find that, although the structural energy differences seem to be overestimated by the the......The authors have studied the crystal structure of all the 3d, 4d, and 5d transition metals at zero pressure and temperature by means of the linear muffin-tin orbital method and Andersen's force theorem. They find that, although the structural energy differences seem to be overestimated...

  12. Scintillation and optical properties of Ce{sup 3+}-doped CaGdAl{sub 3}O{sub 7} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Masaki, E-mail: masaki.mori.mz4@ms.naist.jp [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan); Nakauchi, Daisuke; Okada, Go [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan); Fujimoto, Yutaka [Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai, 980-8579 (Japan); Kawaguchi, Noriaki [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan); Koshimizu, Masanori [Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai, 980-8579 (Japan); Yanagida, Takayuki [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192 (Japan)

    2017-06-15

    The single crystals of 0, 0.6, 1, 1.6 and 2 mol% Ce doped CaGdAl{sub 3}O{sub 7} (Ce:CGAM) were grown by the Floating Zone method, and investigated on photoluminescence (PL) and scintillation properties. In the PL spectra, a broad emission appeared over 380–500 nm under 280 and 360 nm excitations with the quantum yield of 33.8–38.8%. Under a vacuum ultraviolet excitation (90 nm) using a synchrotron source, non-doped CGAM single crystal showed broad emissions over 250–650 nm. The PL decay time profiles followed a monotonic exponential decay with a decay time constant of around 33 ns. The scintillation spectra were similar to those of PL. All of the samples exhibited a clear photoabsorption peak and Compton edge in the pulse height spectra measured under {sup 137}Cs γ-ray irradiation, and the absolute scintillation light yield (LY) was highest for the 2% Ce-doped sample with the value of 3300±300 ph/MeV. The scintillation decay profiles were approximated by a third order exponential decay function, and the extracted decay time of Ce{sup 3+} emission component was around 36–44 ns. Among all the samples, 2%Ce:CGAM single crystal sample showed the best afterglow level as a scintillator under X-ray irradiation. - Highlights: •Ce{sup 3+}-doped CaGdAl{sub 3}O{sub 7} single crystals were synthesized by the FZ method. •Optical and scintillation properties of Ce{sup 3+}-doped CaGdAl{sub 3}O{sub 7} were investigated. •Photoabsorption peak in a pulse height spectrum was clearly observed under γ-rays.

  13. Continuous-wave and acousto-optically Q-switched 1066 nm laser performance of a novel Nd:GdTaO4 crystal

    Science.gov (United States)

    Ma, Yufei; He, Ying; Peng, Zhenfang; Sun, Haiyue; Peng, Fang; Yan, Renpeng; Li, Xudong; Yu, Xin; Zhang, Qingli; Ding, Shoujun

    2018-05-01

    A diode-pumped acousto-optically (AO) Q-switched 1066 nm laser with a novel Nd:GdTaO4 crystal was demonstrated for the first time to the best of our knowledge. The optimization selection of output coupler was carried out in the continuous-wave (CW) operation. After that the pulsed Nd:GdTaO4 laser performances using different modulation repetition rates of 10 kHz and 20 kHz were investigated. At an absorbed pump power of 10 W and repetition rates of 10 kHz, the obtained minimum pulse width was 28 ns and the maximum peak power was 5.4 kW.

  14. Structure, magnetism, and transport of single-crystalline R NiSi3 (R = Y, Gd-Tm, Lu)

    Science.gov (United States)

    Arantes, Fabiana R.; Aristizábal-Giraldo, Deisy; Masunaga, Sueli H.; Costa, Fanny N.; Ferreira, Fabio F.; Takabatake, Toshiro; Mendonça-Ferreira, Leticie; Ribeiro, Raquel A.; Avila, Marcos A.

    2018-04-01

    We report on the physical properties of the intermetallic series R NiSi3 (R =Y , Gd-Tm, Lu). High quality single crystals with platelike morphology were grown using the Sn flux method. X-ray powder diffraction data show that this series crystallizes in the orthorhombic space group Cmmm, and Laue patterns indicate that the b axis remains perpendicular to the plane of the plates. Magnetization measurements show anisotropic antiferromagnetic ground states for R = Gd-Tm with Néel temperatures ranging from TN=2.6 K (TmNiSi3) up to 32.2 K (TbNiSi3), as well as metamagnetic transitions that in some cases appear together with hysteresis (TbNiSi3,DyNiSi3, and HoNiSi3). The easy axis changes from a axis to b axis on going from R = Gd-Ho to R = Er-Tm. All transitions from antiferromagnetic to paramagnetic states are clearly marked by sharp peaks in specific heat as well as in the derivative of resistivity measurements, which show metallic temperature dependence for all compounds and residual values in the range of 1 μ Ω cm . DyNiSi3 has two close phase transitions, while HoNiSi3 presents distinct critical temperatures for applied fields in the a or c directions (10.4 and 6.3 K, respectively), pointing to possible component-specific ordering of the local magnetic moments.

  15. Solvothermal syntheses, crystal structures, and properties of lanthanide(III) thioarsenates [Ln(dien)2(μ-1κ,2κ2-AsS4)]n (Ln==Sm, Eu, Gd) and [Ln(dien)2(1κ2-AsS4)] (Ln==Tb, Dy, Ho)

    International Nuclear Information System (INIS)

    Wang, Fang; Tang, Chunying; Chen, Ruihong; Zhang, Yong; Jia, Dingxian

    2013-01-01

    Solvothermal reactions of Ln 2 O 3 , As and S in diethylenetriamine (dien) at 170 °C for 6 days afforded two structural types of lanthanide thioarsenates with the general formulae [Ln(dien) 2 (μ-1κ,2κ 2 -AsS 4 )] n [Ln=Sm(1), Eu(2), Gd(3)] and [Ln(dien) 2 (1κ 2 -AsS 4 )] [Ln=Tb(4), Dy(5), Ho(6)]. The Ln 2 O 3 oxides were converted to [Ln(dien) 2 ] 3+ complex units in the solvothermal reactions. The As atom binds four S atoms, forming a tetrahedral AsS 4 unit. In 1−3, the AsS 4 units interconnect the [Ln(dien) 2 ] 3+ cations via Ln−S bonds as tridentate μ-1κ,2κ 2 -AsS 4 bridging ligands, resulting in the neutral coordination polymers [Ln(dien) 2 (μ-1κ,2κ 2 -AsS 4 )] n (Ln1). In 4−6, the AsS 4 units coordinate with the Ln 3+ ion of [Ln(dien) 2 ] 3+ as 1κ 2 -AsS 4 chelating ligands to form neutral coordination compounds [Ln(dien) 2 (1κ 2 -AsS 4 )] (Ln2). The Ln 3+ ions are in nine- and eight-coordinated environments in Ln1 and Ln2, respectively. The formation of Ln1 and Ln2 is related with ionic size of the Ln 3+ ions. Optical absorption spectra showed that 1−6 have potential use as semiconductors with the band gaps in the range 2.18−3.21 eV. - Graphical abstract: Two types of Ln-thioarsenates [Ln(dien) 2 (μ-1κ,2κ 2 -AsS 4 )] n and [Ln(dien) 2 (1κ 2 -AsS 4 )] were prepared by solvothermal methods and the soft Lewis basic AsS 4 3– ligand to Ln(III) centers with polyamine co-ligand was obtained. Display Omitted - Highlights: • Lanthanide thioarsenates were prepared by solvothermal methods. • The soft Lewis basic AsS 4 ligand coordinate Ln 3+ ions with coexistence polyamine ligands. • Two structural types of Ln-thioarsenates with structural turnover at Tb were obtained along Ln series. • The Ln-thioarsenates are potential semiconductors with optical band gaps in the range 2.18−3.21 eV

  16. Spectroscopic analysis and efficient diode-pumped 1.9 μm Tm3+-doped β'-Gd2(MoO4)3 crystal laser.

    Science.gov (United States)

    Tang, Jianfeng; Chen, Yujin; Lin, Yanfu; Gong, Xinghong; Huang, Jianhua; Luo, Zundu; Huang, Yidong

    2011-07-04

    Tm3+-doped β'-Gd2(MoO4)3 single crystal was grown by the Czochralski method. Spectroscopic analysis was carried out along different polarizations. End-pumped by a quasi-cw diode laser at 795 nm in a plano-concave cavity, an average laser output power of 58 mW around 1.9 μm was achieved in a 0.93-mm-thick crystal when the output coupler transmission was 7.1%. The absorbed pump threshold was 8 mW and the slope efficiency of the laser was 57%. This crystal has smooth and broad gain curve around 1.9 μm, which shows that it is also a potential gain medium for tunable and short pulse lasers.

  17. Role of anion doping on electronic structure and magnetism of GdN by first principles calculations

    KAUST Repository

    Zhang, Xuejing; Mi, Wenbo; Guo, Zaibing; Cheng, Yingchun; Chen, Guifeng; Bai, Haili

    2014-01-01

    We have investigated the electronic structure and magnetism of anion doped GdN1-yXy (X = B, C, O, F, P, S and As) systems by first-principles calculations based on density functional theory. GdN 1-yXy systems doped by O, C, F, P, and S atoms are more stable than those doped by B and As atoms because of relatively high binding energies. The anion doping and the N defect states modify the density of states at the Fermi level, resulting in a decrease in spin polarization and a slight increase in the magnetic moment at the Gd and N sites. © 2014 The Royal Society of Chemistry.

  18. Multiple crossovers between positive and negative magnetoresistance versus field due to fragile spin structure in metallic GdPd3

    Science.gov (United States)

    Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Johnston, D. C.

    2017-01-01

    Studies on the phenomenon of magnetoresistance (MR) have produced intriguing and application-oriented outcomes for decades–colossal MR, giant MR and recently discovered extremely large MR of millions of percents in semimetals can be taken as examples. We report here the discovery of novel multiple sign changes versus applied magnetic field of the MR in the cubic intermetallic compound GdPd3. Our study shows that a very strong correlation between magnetic, electrical and magnetotransport properties is present in this compound. The magnetic structure in GdPd3 is highly fragile since applied magnetic fields of moderate strength significantly alter the spin arrangement within the system–a behavior that manifests itself in the oscillating MR. Intriguing magnetotransport characteristics of GdPd3 are appealing for field-sensitive device applications, especially if the MR oscillation could materialize at higher temperature by manipulating the magnetic interaction through perturbations caused by chemical substitutions. PMID:28211520

  19. Two-dimensional photonic crystal accelerator structures

    Directory of Open Access Journals (Sweden)

    Benjamin M. Cowan

    2003-10-01

    Full Text Available Photonic crystals provide a method of confining a synchronous speed-of-light mode in an all-dielectric structure, likely a necessary feature in any optical accelerator. We explore computationally a class of photonic crystal structures with translational symmetry in a direction transverse to the electron beam. We demonstrate synchronous waveguide modes and discuss relevant parameters of such modes. We then explore how accelerator parameters vary as the geometry of the structure is changed and consider trade-offs inherent in the design of an accelerator of this type.

  20. Crystal structure of enolase from Drosophila melanogaster.

    Science.gov (United States)

    Sun, Congcong; Xu, Baokui; Liu, Xueyan; Zhang, Zhen; Su, Zhongliang

    2017-04-01

    Enolase is an important enzyme in glycolysis and various biological processes. Its dysfunction is closely associated with diseases. Here, the enolase from Drosophila melanogaster (DmENO) was purified and crystallized. A crystal of DmENO diffracted to 2.0 Å resolution and belonged to space group R32. The structure was solved by molecular replacement. Like most enolases, DmENO forms a homodimer with conserved residues in the dimer interface. DmENO possesses an open conformation in this structure and contains conserved elements for catalytic activity. This work provides a structural basis for further functional and evolutionary studies of enolase.

  1. Crystal structure of isomeric boron difluoride acetylnaphtholates

    International Nuclear Information System (INIS)

    Bukvetskij, B.V.; Fedorenko, E.V.; Mirochnik, A.G.; Karasev, V.E.

    2006-01-01

    Crystal structures of luminescent isomeric acetylnaphtholates of boron difluoride are investigated. Full X-ray structural analysis is done at 293 K. Coordinated of atoms, bond angles, bond lengths, interatomic distances are determined. Results of comparative evaluations of the isomers are represented [ru

  2. Crystal structure of levomepromazine maleate

    Directory of Open Access Journals (Sweden)

    Gyula Tamás Gál

    2016-05-01

    Full Text Available The asymmetric unit of the title salt, C19H25N2OS+·C4H3O4− [systematic name: (S-3-(2-methoxyphenothiazin-10-yl-N,N,2-trimethylpropanaminium hydrogen maleate], comprises two (S-levomepromazine cations and two hydrogen maleate anions. The conformations of the two cations are similar. The major difference relates to the orientation of the methoxy substituent at the phenothiazine ring system. The crystal components form a three-dimensional supramolecular network via N—H...O, C—H...O and C—H...π interactions. A comparison of the conformations of the levomepromazine cations with those of the neutral molecule and similar protonated molecules reveals significant conformational flexibility of the phenothiazine ring system and the substituent at the phenothiazine N atom.

  3. Data of evolutionary structure change: 1RAAA-3GD5F [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1RAAA-3GD5F 1RAA 3GD5 A F ANPLYQKHIISINDLSRDDLNLVLATAAKLKANPQPELL...ARGAHILYTDVWTHR---LQLFEQ----YQINAALLNCAAAEAIVLHCLPAHRGEEITDEVMEGPRSRIWDEAENRLHAQK...ex> 1RAA A 1RAAA DML...> A 1RAAA PLPRV--DEIA...dbChain> 1RAAA TEFSGNVPVLN HHHH

  4. Data of evolutionary structure change: 1RAAA-3GD5A [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1RAAA-3GD5A 1RAA 3GD5 A A ANPLYQKHIISINDLSRDDLNLVLATAAKLKANPQPELL...ARGAHILYTDVWTHR---LQLFEQYQ----INAALLNCAAAEAIVLHCLPAHRGEEITDEVMEGPRSRIWDEAENRLHAQK...index> 1RAA A 1RAAA ... 1RAA A 1RAAA...ntryChain> 1RAA A 1RAAA

  5. Data of evolutionary structure change: 1RAAA-3GD5E [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1RAAA-3GD5E 1RAA 3GD5 A E ANPLYQKHIISINDLSRDDLNLVLATAAKLKANPQPELL...LRDPFEAARGAHILYTDVWTHRLQLFEQYQINAAL------------LNC--AAAEAIVLHCLPAHRGEEITDEVMEGPRS...ID> 0 1RAA A 1RAAA 1RAA A 1RAAA1RAA A 1RAAA TEFSGNVPVLN

  6. Development and measurement of luminescence properties of Ce-doped Cs2LiGdBr6 crystals irradiated with X-ray, γ-ray and proton beam

    Science.gov (United States)

    Jang, Jonghun; Kim, H. J.; Rooh, Gul; Kim, Sunghwan

    2017-12-01

    The effect of higher Ce-concentration on the luminescence and scintillation properties of Cs2LiGdBr6 single crystals are studied. We used the Bridgman method for the growth of Ce-doped Cs2LiGdBr6 single crystals. Luminescence properties of the grown crystals are measured by X-ray and proton excitations. We measured the pulse height and fluorescence decay time spectra of Cs2LiGdBr6:Ce3+ with a bi-alkali photo multiplier tube (PMT) under γ-ray excitation from 137Cs source. Improvements in the scintillation properties are observed with the increase of Ce-concentration in the lattice. Detailed procedure of the crystal growth is also discussed.

  7. Some particularities of impurity center structure in concentrated solid solutions MeF2-GdF3, where Me-Ca2+, Sr2+ and Ba2+

    International Nuclear Information System (INIS)

    Karelin, V.V.; Orlov, Yu.N.; Bozhevol'nov, V.E.; Ivanov, L.N.

    1981-01-01

    The monocrystalline CaF 2 -GdF 3 , SrF 2 -GdF 3 and BaF 2 -GdF 3 systems are studied using the methods of EPR, photo-, radio-, cathode- and thermoluminescence. It is shown that the structure of fluorite solid solutions changes considerably with the growth of the rare earth component concentration. At that, in the systems investigated at least three concentration regions can be singled out: (up to 1%; from 1 to 15%, and > 15% GdF 3 ) which are characterized by their certain selection of impurity centres [ru

  8. Magnetic properties of the filled skutterudite-type structure compounds GdRu4P12 and TbRu4P12 synthesized under high pressure

    OpenAIRE

    Sekine, C; Uchiumi, T; Shirotani, I; Matsuhira, kazuyuki; Sakakibara, T; Goto, T; Yagi, T

    2000-01-01

    We have succeeded in synthesizing filled skutterudite-type structure compounds GdRu4P12 and TbRu4P12 under high pressure. The magnetic properties of GdRu4P12 and TbRu4P12 have been studied by means of electrical resistivity, magnetic susceptibility, and magnetization measurements. Magnetic experiments suggest that the Gd and Tb ions in the compounds have trivalent state. The compound GdRu4P12 displays features that suggest the occurrence of antiferromagnetic ordering below TN=22 K. In TbRu4P1...

  9. A comparative study on the luminescence properties of Ce3+/Tb3+ doped Gd-based host nanomaterials

    Science.gov (United States)

    Jadhao, Charushila Vasant; Rani, Barkha; Sahu, Niroj Kumar

    2018-04-01

    A comparative study on the crystal phases and their respective luminescence behaviour of Gd3+ based host materials such as GdPO4, GdF3, GdVO4 and Gd2O3 sensitized with 7at.% Ce3+ and activated with 5 at.% Tb3+ have been reported. The nanomaterials were prepared by polyol method using ethylene glycol as solvent and found to have different crystal structures such as monoclinic, orthorhombic, tetragonal and cubic phase. Clear characteristics emission from Tb3+ has been observed in all the samples when excited in the absorption wavelength of Ce3+ and Gd3+ (˜280 nm). Among all the above materials, intense emission of Tb3+ is found in GdPO4 followed by GdF3, Gd2O3 and GdVO4 respectively. The Tb3+ emission is strongly influenced by the energy transfer process and crystal structure of the host materials and hence this study will be important for choosing suitable materials for display devices and biomedical applications.

  10. Crystal structure of rubidium methyldiazotate

    Directory of Open Access Journals (Sweden)

    Tobias Grassl

    2017-02-01

    Full Text Available The title compound, Rb+·H3CN2O−, has been crystallized in liquid ammonia as a reaction product of the reductive ammonolysis of the natural compound streptozocin. Elemental rubidium was used as reduction agent as it is soluble in liquid ammonia, forming a blue solution. Reductive bond cleavage in biogenic materials under kinetically controlled conditions offers a new approach to gain access to sustainably produced raw materials. The anion is nearly planar [dihedral angle O—N—N—C = −0.4 (2°]. The Rb+ cation has a coordination number of seven, and coordinates to five anions. One anion is bound via both its N atoms, one by both O and N, two anions are bound by only their O atoms, and the last is bound via the N atom adjacent to the methyl group. The diazotate anions are bridged by cations and do not exhibit any direct contacts with each other. The cations form corrugated layers that propagate in the (-101 plane.

  11. Effect of Gd3+ substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe2O4

    Science.gov (United States)

    Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Kumar, Arun; Singh, Mahavir

    2017-03-01

    Nanoparticles of CoGdxFe2-xO4 with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd3+ substitution effect on different properties of nanocrystalline CoFe2O4 has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd3+ ions occupy the octahedral site in CoFe2O4. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd3+ substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd3+ substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd3+ substitution for Fe3+ at the octahedral sites. Low dielectric loss suggested the applicability of Gd3+ doped CoFe2O4 nanoparticles for high frequency microwave device applications.

  12. Electronic structure and exchange interactions in GdB{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Baranovskiy, A., E-mail: andriy.baranovskiy@gmail.com; Grechnev, A.

    2015-02-01

    The electronic structure of the antiferromagnetic Shastry–Sutherland compound GdB{sub 4} has been analyzed with density functional theory and the all-electron full-potential linearized augmented-plane wave (FP-LAPW) code. Different magnetic configurations, including the realistic dimer one, have been considered. The exchange interactions were found to be J{sub 1}/k{sub B}=−12K and J{sub 2}/k{sub B}=−2–0.8K, where, J{sub 1} and J{sub 2} are the diagonal exchange interaction and the exchange interaction along the edges of a square, respectively. - Highlights: • Electronic structure of AFM Shastry–Sutherland compound GB{sub 4} is calculated. • The mechanism of exchange parameters evaluation within Heisenberg model is proposed. • Calculated exchange parameters are found to be in agreement with experimental data. • Higher-order exchange interactions are important for dimer structure stabilizing.

  13. Alignment structures in ferroelectric liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Islam, N.U

    1998-07-01

    Although for many years liquid crystals were of purely scientific interest, they have now become ubiquitous in everyday life. The use of the nematic liquid crystal phase in flat panel display applications has been the main factor in this popularity. However, with the advent of the SuperTwist Nematic (STN) device, the limits to which this phase could be exploited for display applications was perhaps reached. With the discovery by Clark et al. of the Surface Stabilised Ferroelectric Liquid Crystal (SSFLC) configuration, the possibility arose of using chiral smectic liquid crystals to create large area, passively addressed, fast switching, flat panel displays. Unfortunately, the structures that form within smectic liquid crystals, and the dynamics of the switching within these, are still not fully understood. In this thesis we address the former of these, making a detailed the study of the structures that form within tilted smectic liquid crystal devices. We present here the first complete theoretical and experimental study of various different ferroelectric liquid crystal materials, where we employed theoretical models based on a simple set of assumptions to understand the behaviour of a set of increasingly complex experimental systems. We started with the simplest of these, Freely Suspended Smectic Films (FSSFs) and then worked with progressively more realistic systems in the form of homeotropically, and later, homogeneously aligned liquid crystal cells. The equilibrium structures that form get particularly complex in the last case, taking the form of tilted and chevron layering structures. In each of these cases, the predictions of the modelling are compared with our experimental results. Further, we present here the first model of the chevron cusp that seeks to include the effects of biaxiality in the S{sub C} phase. We also present a model that seeks to analyse the stability of the chevron layering structure and its relationship with tilted layers. This includes

  14. Alignment structures in ferroelectric liquid crystals

    International Nuclear Information System (INIS)

    Islam, N.U.

    1998-01-01

    Although for many years liquid crystals were of purely scientific interest, they have now become ubiquitous in everyday life. The use of the nematic liquid crystal phase in flat panel display applications has been the main factor in this popularity. However, with the advent of the SuperTwist Nematic (STN) device, the limits to which this phase could be exploited for display applications was perhaps reached. With the discovery by Clark et al. of the Surface Stabilised Ferroelectric Liquid Crystal (SSFLC) configuration, the possibility arose of using chiral smectic liquid crystals to create large area, passively addressed, fast switching, flat panel displays. Unfortunately, the structures that form within smectic liquid crystals, and the dynamics of the switching within these, are still not fully understood. In this thesis we address the former of these, making a detailed the study of the structures that form within tilted smectic liquid crystal devices. We present here the first complete theoretical and experimental study of various different ferroelectric liquid crystal materials, where we employed theoretical models based on a simple set of assumptions to understand the behaviour of a set of increasingly complex experimental systems. We started with the simplest of these, Freely Suspended Smectic Films (FSSFs) and then worked with progressively more realistic systems in the form of homeotropically, and later, homogeneously aligned liquid crystal cells. The equilibrium structures that form get particularly complex in the last case, taking the form of tilted and chevron layering structures. In each of these cases, the predictions of the modelling are compared with our experimental results. Further, we present here the first model of the chevron cusp that seeks to include the effects of biaxiality in the S C phase. We also present a model that seeks to analyse the stability of the chevron layering structure and its relationship with tilted layers. This includes an

  15. Solvothermal syntheses, crystal structures, and properties of lanthanide(III) thioarsenates [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} (Ln==Sm, Eu, Gd) and [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] (Ln==Tb, Dy, Ho)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fang; Tang, Chunying; Chen, Ruihong; Zhang, Yong; Jia, Dingxian, E-mail: jiadingxian@suda.edu.cn

    2013-10-15

    Solvothermal reactions of Ln{sub 2}O{sub 3}, As and S in diethylenetriamine (dien) at 170 °C for 6 days afforded two structural types of lanthanide thioarsenates with the general formulae [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} [Ln=Sm(1), Eu(2), Gd(3)] and [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] [Ln=Tb(4), Dy(5), Ho(6)]. The Ln{sub 2}O{sub 3} oxides were converted to [Ln(dien){sub 2}]{sup 3+} complex units in the solvothermal reactions. The As atom binds four S atoms, forming a tetrahedral AsS{sub 4} unit. In 1−3, the AsS{sub 4} units interconnect the [Ln(dien){sub 2}]{sup 3+} cations via Ln−S bonds as tridentate μ-1κ,2κ{sup 2}-AsS{sub 4} bridging ligands, resulting in the neutral coordination polymers [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} (Ln1). In 4−6, the AsS{sub 4} units coordinate with the Ln{sup 3+} ion of [Ln(dien){sub 2}]{sup 3+} as 1κ{sup 2}-AsS{sub 4} chelating ligands to form neutral coordination compounds [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] (Ln2). The Ln{sup 3+} ions are in nine- and eight-coordinated environments in Ln1 and Ln2, respectively. The formation of Ln1 and Ln2 is related with ionic size of the Ln{sup 3+} ions. Optical absorption spectra showed that 1−6 have potential use as semiconductors with the band gaps in the range 2.18−3.21 eV. - Graphical abstract: Two types of Ln-thioarsenates [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} and [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] were prepared by solvothermal methods and the soft Lewis basic AsS{sub 4}{sup 3–} ligand to Ln(III) centers with polyamine co-ligand was obtained. Display Omitted - Highlights: • Lanthanide thioarsenates were prepared by solvothermal methods. • The soft Lewis basic AsS{sub 4} ligand coordinate Ln{sup 3+} ions with coexistence polyamine ligands. • Two structural types of Ln-thioarsenates with structural turnover at Tb were obtained along Ln series. • The Ln-thioarsenates are potential semiconductors

  16. Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study

    Energy Technology Data Exchange (ETDEWEB)

    Ritter, C [Institut Lauer-Langevin, Grenoble (France); Dhar, S K [TIFR, Mumbai (India); Kulkarni, R [TIFR, Mumbai (India); Provino, A [Inst. SPIN-CNR, Genova (Italy); Univ. of Genova (Italy); Ames Lab., Ames, IA (United States); Paudyal, Durga [Ames Lab., Ames, IA (United States); Manfrinetti, Pietro [Inst. SPIN-CNR, Genova (Italy); Univ. of Genova (Italy); Ames Lab., Ames, IA (United States); Gschneidner, Karl A [Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)

    2014-08-14

    The synthesis of the new equiatomic RScSb ( R = La-Nd, Sm, Gd-Tm, Lu, Y) compounds has been recently reported. These rare earth compounds crystallize in two different crystal structures, adopting the CeScSi-type ( I 4/ mmm) for the lighter R (La-Nd, Sm) and the CeFeSi-type (P4 /nmm) structure for the heavier R ( R = Gd-Tm, Lu, Y). Here we report the results of neutron diffraction, magnetization and heat capacity measurements on some of these compounds ( R = Ce, Pr, Nd, Gd and Tb). Band structure calculations have also been performed on CeScSb and GdScGe (CeScSi-type), and on GdScSb and TbScSb (CeFeSi-type) to compare and understand the exchange interactions in CeScSi and CeFeSi structure types. The neutron diffraction investigation shows that all five compounds order magnetically, with the highest transition temperature of 66 K in TbScSb and the lowest of about 9 K in CeScSb. The magnetic ground state is simple ferromagnetic (τ = [0 0 0]) in CeScSb, as well in NdScSb for 32 >T > 22 K. Below 22 K a second magnetic transition, with propagation vector τ = [¼ ¼ 0], appears in NdScSb. PrScSb has a magnetic structure within, determined by mostly ferromagnetic interactions and antiferromagnetic alignment of the Pr-sites connected through the I-centering ( τ = [1 0 0]). A cycloidal spiral structure with a temperature dependent propagation vector τ = [δ δ ½] is found in TbScSb. The results of magnetization and heat capacity lend support to the main conclusions derived from neutron diffraction. As inferred from a sharp peak in magnetization, GdScSb orders antiferromagnetically at 56 K. First principles calculations show lateral shift of spin split bands towards lower energy from the Fermi level as the CeScSi-type structure changes to the CeFeSi-type structure. This rigid shift may force the system to transform from exchange split ferromagnetic state to the antiferromagnetic state in RScSb compounds (as seen for example in GdScSb and TbScSb) and is proposed to

  17. Information and crystal structure estimation

    International Nuclear Information System (INIS)

    Wilkins, S.W.; Commonwealth Scientific and Industrial Research Organization, Clayton; Varghese, J.N.; Steenstrup, S.

    1984-01-01

    The conceptual foundations of a general information-theoretic based approach to X-ray structure estimation are reexamined with a view to clarifying some of the subtleties inherent in the approach and to enhancing the scope of the method. More particularly, general reasons for choosing the minimum of the Shannon-Kullback measure for information as the criterion for inference are discussed and it is shown that the minimum information (or maximum entropy) principle enters the present treatment of the structure estimation problem in at least to quite separate ways, and that three formally similar but conceptually quite different expressions for relative information appear at different points in the theory. One of these is the general Shannon-Kullback expression, while the second is a derived form pertaining only under the restrictive assumptions of the present stochastic model for allowed structures, and the third is a measure of the additional information involved in accepting a fluctuation relative to an arbitrary mean structure. (orig.)

  18. Timing characteristics of Ce doped Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12} single crystals in comparison with CsI(Tl) scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, M.; Singh, A.K.; Singh, S.G.; Sen, S.; Gadkari, S.C. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Desai, V.V.; Nayak, B.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India)

    2015-10-15

    Single crystals of Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12}:Ce with B codopants were successfully grown using the Czochralski technique. The timing characteristics of the crystal was measured by coupling the crystal to photomultiplier tubes (PMT) or silicon photodiodes [Si(PIN)]. The two prompt γ-rays emitted in a cascade from {sup 60}Co or {sup 22}Na source were detected in coincidence using Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12}:Ce,B crystal detectors and a BaF{sub 2} detector. The time resolution of these crystals are observed to be better than that measured for CsI:Tl crystal coupled to PMT or Si(PIN) in an identical measurement setup. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Relativistic electronic structure calculations on endohedral Gd rate at C60, La rate at C60, Gd rate at C74, and La rate at C74

    International Nuclear Information System (INIS)

    Lu, J.; Zhang, X.; Zhao, X.

    2000-01-01

    Relativistic discrete-variational local density functional calculations on endohedral Gd rate at C 60 , La rate at C 60 ,Gd rate at C 74 , and La rate at C 74 are performed. All the C 60 - and C 74 -derived levels are lowered upon endohedral Gd and La doping. Both the Gd (4f 7 5d 1 6s 2 ) and La (5d 1 6s 2 ) atoms only donate their two 6s valence electrons to the cages, leaving behind their 5d electrons when they are placed at the cage centers. Compared with large-band-gap C 60 , small-band-gap C 74 and Gd (La)-metallofullerenes have strong both electron-donating and electron-accepting characters, and the calculated ionization potentials and electron affinities for them agree well with the available experimental data. (orig.)

  20. Shear induced structures in crystallizing cocoa butter

    Science.gov (United States)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  1. Magnetic properties of GdMnO3 nanoparticles embedded in mesoporous silica

    Science.gov (United States)

    Tajiri, Takayuki; Mito, Masaki; Deguchi, Hiroyuki; Kohno, Atsushi

    2018-05-01

    Perovskite manganite GdMnO3 nanoparticles were synthesized using mesoporous silica as a template, and their magnetic properties and crystal structure were investigated. Powder X-ray diffraction data indicated successful synthesis of the GdMnO3 nanoparticles, with mean particle sizes of 13.9 and 20.9 nm. The lattice constants for the nanoparticles were slightly different from those for the bulk material and varied with the particle size. The magnetic transition temperatures for the nanoparticles were higher than those of the bulk crystal. The synthesized GdMnO3 nanoparticles exhibited superparamagnetic behaviors: The blocking temperature, coercive field, and transition temperature depended on the particle size. Magnetic measurements and crystal structure analysis suggest that the changes in the magnetic properties for GdMnO3 nanoparticles can be attributed to the modulation of the crystallographic structure.

  2. Structure analysis on synthetic emerald crystals

    Science.gov (United States)

    Lee, Pei-Lun; Lee, Jiann-Shing; Huang, Eugene; Liao, Ju-Hsiou

    2013-05-01

    Single crystals of emerald synthesized by means of the flux method were adopted for crystallographic analyses. Emerald crystals with a wide range of Cr3+-doping content up to 3.16 wt% Cr2O3 were examined by X-ray single crystal diffraction refinement method. The crystal structures of the emerald crystals were refined to R 1 (all data) of 0.019-0.024 and w R 2 (all data) of 0.061-0.073. When Cr3+ substitutes for Al3+, the main adjustment takes place in the Al-octahedron and Be-tetrahedron. The effect of substitution of Cr3+ for Al3+ in the beryl structure results in progressively lengthening of the Al-O distance, while the length of the other bonds remains nearly unchanged. The substitution of Cr3+ for Al3+ may have caused the expansion of a axis, while keeping the c axis unchanged in the emerald lattice. As a consequence, the Al-O-Si and Al-O-Be bonding angles are found to decrease, while the angle of Si-O-Be increases as the Al-O distance increases during the Cr replacement.

  3. Synthesis, characterization and crystal structure of a ...

    African Journals Online (AJOL)

    The Mo atom in the complex is in octahedral coordination. Thermal stability of the complex has also been studied. KEY WORDS: Molybdenum complex, Hydrazone ligand, Crystal structure, X-ray diffraction, Thermal property. Bull. Chem. Soc. Ethiop. 2014, 28(3), 409-414. DOI: http://dx.doi.org/10.4314/bcse.v28i3.10 ...

  4. Synthesis, crystal structure, thermal analysis and dielectric ...

    Indian Academy of Sciences (India)

    [13] Perry C H and Lowdes R P 1969 J. Chem. Phys. 51 3648. [14] Sheldrick G M 1997 SHELXS9, Program for the Refinement of Crystal Structures (Germany: University of Gottingen). [15] Loukil M, Kabadou A, Salles Ph and Ben Salah A 2004 Chem. Phys. 300 247. [16] Rolies M M and De Ranter C J 1978 Acta Crystallogr.

  5. Growth, spectral properties, and laser demonstration of Nd:(Lu0.5Gd0.5)2SiO5 crystal

    International Nuclear Information System (INIS)

    Li, D Z; Xu, X D; Wu, F; Xia, C T; Zhang, J; Ma, J; Cong, Z H; Tang, D Y; Zhu, H M; Chen, X Y; Xu, J

    2011-01-01

    A Nd:(Lu 0.5 Gd 0.5 ) 2 SiO 5 (Nd:LGSO) crystal has been grown by the Czochralski method. The cell parameters were analyzed with X-ray diffraction (XRD). The Judd-Ofelt intensity parameters Ω 2,4,6 were obtained to be 5.37, 1.63, and 5.57×10 -20 cm 2 , respectively. The absorption and emission cross sections and branching ratios were calculated. The Nd:LGSO crystal reveals a broadband emission feature (FWHM = 9.8 nm), which shows potential as gain medium for ultrashort pulse lasers. The radiative and fluorescence lifetimes are 299 and 230 μs, respectively, resulting in a quantum efficiency of 77%. Pumped by a laser diode, the maximum continuous wave (CW) output power of 444 mW and a slope efficiency of 17.7% have been obtained

  6. Growth, spectral properties, and laser demonstration of Nd:(Lu0.5Gd0.5)2SiO5 crystal

    Science.gov (United States)

    Li, D. Z.; Xu, X. D.; Zhang, J.; Cong, Z. H.; Tang, D. Y.; Ma, J.; Zhu, H. M.; Chen, X. Y.; Wu, F.; Xia, C. T.; Xu, J.

    2011-09-01

    A Nd:(Lu0.5Gd0.5)2SiO5 (Nd:LGSO) crystal has been grown by the Czochralski method. The cell parameters were analyzed with X-ray diffraction (XRD). The Judd-Ofelt intensity parameters Ω2,4,6 were obtained to be 5.37, 1.63, and 5.57×10-20 cm2, respectively. The absorption and emission cross sections and branching ratios were calculated. The Nd:LGSO crystal reveals a broadband emission feature (FWHM = 9.8 nm), which shows potential as gain medium for ultrashort pulse lasers. The radiative and fluorescence lifetimes are 299 and 230 μs, respectively, resulting in a quantum efficiency of 77%. Pumped by a laser diode, the maximum continuous wave (CW) output power of 444 mW and a slope efficiency of 17.7% have been obtained.

  7. Magnetic ordering of GdMn2

    International Nuclear Information System (INIS)

    Ouladdiaf, B.; Ritter, C.; Ballou, R.; Deportes, J.

    1999-01-01

    Complete text of publication follows. GdMn 2 crystallizes in the C15 cubic Laves phase structure. Within this structure Mn atoms lie at the vertices of regular tetrahedra stacked in the diamond arrangement connected by sharing vertices, leading to a strong geometric frustration. An antiferromagnetic magnetic order sets in below T N ∼ 105 K. It gives rise to a large magnetovolume effect (ΔV/V ∼ 1%). Thermal expansion data show two anomalies at 105 K and 35 K. The second anomaly was often interpreted as the ferromagnetic ordering of Gd sublattice. Moessbauer data indicate however, that Gd sublattice orders at T N ∼ 105 K as the Mn moments. Elastic neutron scattering measurements were performed using short wavelength neutron beam (λ = 0.5 A) on D9 at ILL. No magnetic contribution to the nuclear peaks was found excluding thereby any K = [0 0 0] component. However antiferromagnetic peaks indexed by a propagation vector [2/3 2/3 0] were observed leading to a non collinear magnetic arrangement of both Mn and Gd sublattices. The results are discussed by invoking the geometric frustration associated with the Mn atomic packing and the singlet state of the Gd ions. (author)

  8. Magnetic and structural studies on nanostructured Gd/Cr multilayer films

    International Nuclear Information System (INIS)

    Gadioli, G.Z.; Rouxinol, F.P.; Gelamo, R.V.; Cardoso, L.P.; Gama, S.; Bica de Moraes, M.A.

    2013-01-01

    Investigations of magnetic phases, transition temperatures and coercivity were performed in multilayered Gd/Cr films as a function of the crystalline state and morphology of the Gd layers. The films were deposited by dc magnetron sputtering at three substrate temperatures, T s , (room temperature, 300 and 500 °C). The Gd and Cr thicknesses were of 10 and 30 nm, respectively. Two series of three films were prepared. In one of the series, the films had a single Gd/Cr bilayer; in the other, 15 bilayers. The discontinuous or granular nature of the Gd layers was revealed by scanning electron microscopy Grazing incidence angle x-ray diffraction was used to investigate the crystalline state of the Gd and Cr layers. These techniques revealed that grain average size and crystalline order increase with increasing T s . From dc magnetic measurements, the co-existence of ferromagnetic and superferromagnetic phases in the Gd layers was observed, and Curie transition temperatures, T C , were determined. High coercive fields at low temperature (2 K) were measured in hysteresis cycles. Field-cooled and zero field-cooled magnetizations as functions of temperature curves exhibited, for some of the samples, a low temperature peak suggesting a freezing transition to a cluster glass state. This was confirmed by complementary ac-susceptibility measurements carried out as a function of temperature, for various frequencies of the ac field. Some results of this work – the decline in T C for decreasing Gd grain size, the high coercive field and its dependence on particle size, and the behavior of the magnetization at low temperatures for the sample deposited at room temperature – are discussed in terms of finite size and surface effects in nanosized particles. - Highlights: • Sputter-deposited Gd/Cr multilayer films with nanostructured Gd layers • Ferromagnetic and superferromagnetic phases are observed. • Ferromagnetic phase dependent of the deposition temperature • Improved

  9. Magnetic exchange in {Gd(III)-radical} complexes: method assessment, mechanism of coupling and magneto-structural correlations.

    Science.gov (United States)

    Gupta, Tulika; Rajeshkumar, Thayalan; Rajaraman, Gopalan

    2014-07-28

    Density functional studies have been performed on ten different {Gd(III)-radical} complexes exhibiting both ferro and antiferromagnetic exchange interaction with an aim to assess a suitable exchange-correlation functional within DFT formalism. This study has also been extended to probe the mechanism of magnetic coupling and to develop suitable magneto-structural correlations for this pair. Our method assessments reveal the following order of increasing accuracy for the evaluation of J values compared to experimental coupling constants: B(40HF)LYP X3LYP < B3LYP < B2PLYP. Grimme's double-hybrid functional is found to be superior compared to other functionals tested and this is followed very closely by the conventional hybrid B3LYP functional. At the basis set front, our calculations reveal that the incorporation of relativistic effect is important in these calculations and the relativistically corrected effective core potential (ECP) basis set is found to yield better Js compared to other methods. The supposedly empty 5d/6s/6p orbitals of Gd(III) are found to play an important role in the mechanism of magnetic coupling and different contributions to the exchange terms are probed using Molecular Orbital (MO) and Natural Bond Orbital (NBO) analysis. Magneto-structural correlations for Gd-O distances, Gd-O-N angles and Gd-O-N-C dihedral angles are developed where the bond angles as well as dihedral angle parameters are found to dictate the sign and strength of the magnetic coupling in this series.

  10. Crystal Structure of Human Enterovirus 71

    Energy Technology Data Exchange (ETDEWEB)

    Plevka, Pavel; Perera, Rushika; Cardosa, Jane; Kuhn, Richard J.; Rossmann, Michael G. (Purdue); (Sentinext)

    2013-04-08

    Enterovirus 71 is a picornavirus associated with fatal neurological illness in infants and young children. Here, we report the crystal structure of enterovirus 71 and show that, unlike in other enteroviruses, the 'pocket factor,' a small molecule that stabilizes the virus, is partly exposed on the floor of the 'canyon.' Thus, the structure of antiviral compounds may require a hydrophilic head group designed to interact with residues at the entrance of the pocket.

  11. Modular crystals as modulated structures

    DEFF Research Database (Denmark)

    Elcoro, L.; Perez-Mato, J.M.; Friese, K.

    2008-01-01

    The use of the superspace formalism is extended to the description and refinement of the homologous series of modular structures with two symmetry-related modules with different orientations. The lillianite homologous series has been taken as a study case. Starting from a commensurate modulated...... composite description with two basic subsystems corresponding to the two different modules, it is shown how a more efficient description can be achieved using so-called zigzag modulation functions. These linear zigzag modulations, newly implemented in the program JANA2006, have very large fixed amplitudes...... and introduce in the starting model the two orientations of the underlying module sublattices. We show that a composite approach with this type of function, which treats the cations and anions as two separate subsystems forming a misfit compound, is the most appropriate and robust method for the refinements....

  12. Correlation between structural, electrical and magnetic properties of GdMnO3 bulk ceramics

    International Nuclear Information System (INIS)

    Samantaray, S.; Mishra, D.K.; Pradhan, S.K.; Mishra, P.; Sekhar, B.R.; Behera, Debdhyan; Rout, P.P.; Das, S.K.; Sahu, D.R.; Roul, B.K.

    2013-01-01

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO 3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO 3 . Room temperature dielectric constant (ε r ) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO 3 at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO 3 sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO 3 . • Possibility of room temperature application of GdMnO 3 as multifunctional material

  13. Correlation between structural, electrical and magnetic properties of GdMnO{sub 3} bulk ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Samantaray, S. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, D.K. [Department of Physics, Institute of Technical Education and Research, S ‘O’ A University, Bhubaneswar 751030, Odisha (India); Pradhan, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, P.; Sekhar, B.R. [Institue of Physics, Sachivalaya Marg, Bhubaneswar, Odisha (India); Behera, Debdhyan [Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, Odisha (India); Rout, P.P.; Das, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Sahu, D.R. [School of Physics, University of the Witwatersrand, Johannesburg (South Africa); Roul, B.K., E-mail: ims@iopb.res.in [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India)

    2013-08-15

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO{sub 3} (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO{sub 3}. Room temperature dielectric constant (ε{sub r}) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO{sub 3} at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO{sub 3} sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO{sub 3}. • Possibility of room temperature application of GdMnO{sub 3} as multifunctional material.

  14. Optical and crystal chemistry studies of Na3Ln(PO4)2-K3Ln(PO4)2 (Ln=Eu, Gd)

    International Nuclear Information System (INIS)

    Mesnaoui, M.; Maazaz, M.

    1987-01-01

    In these systems, large single phase domains are separated by two phase regions. The structural evolution as a function of composition is analysed both by X-ray diffraction and by using Eu 3+ and Gd 3+ as luminescent local structural probes. Due to layer type structure of the K 3 Ln(PO 4 ) 2 phases an exchange reaction resulting in total substitution of sodium for potassium can be carried out with formation of metastable Na 3 Ln(PO 4 ) 2 phases, the structure of which is close to those of the potassium compounds. 10 refs.; 18 figs [fr

  15. Photonic Crystal Laser-Driven Accelerator Structures

    International Nuclear Information System (INIS)

    Cowan, Benjamin M.

    2007-01-01

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques

  16. Crystal structure of riboflavin synthase

    Energy Technology Data Exchange (ETDEWEB)

    Liao, D.-I.; Wawrzak, Z.; Calabrese, J.C.; Viitanen, P.V.; Jordan, D.B. (DuPont); (NWU)

    2010-03-05

    Riboflavin synthase catalyzes the dismutation of two molecules of 6,7-dimethyl-8-(1'-D-ribityl)-lumazine to yield riboflavin and 4-ribitylamino-5-amino-2,6-dihydroxypyrimidine. The homotrimer of 23 kDa subunits has no cofactor requirements for catalysis. The enzyme is nonexistent in humans and is an attractive target for antimicrobial agents of organisms whose pathogenicity depends on their ability to biosynthesize riboflavin. The first three-dimensional structure of the enzyme was determined at 2.0 {angstrom} resolution using the multiwavelength anomalous diffraction (MAD) method on the Escherichia coli protein containing selenomethionine residues. The homotrimer consists of an asymmetric assembly of monomers, each of which comprises two similar {beta} barrels and a C-terminal {alpha} helix. The similar {beta} barrels within the monomer confirm a prediction of pseudo two-fold symmetry that is inferred from the sequence similarity between the two halves of the protein. The {beta} barrels closely resemble folds found in phthalate dioxygenase reductase and other flavoproteins. The three active sites of the trimer are proposed to lie between pairs of monomers in which residues conserved among species reside, including two Asp-His-Ser triads and dyads of Cys-Ser and His-Thr. The proposed active sites are located where FMN (an analog of riboflavin) is modeled from an overlay of the {beta} barrels of phthalate dioxygenase reductase and riboflavin synthase. In the trimer, one active site is formed, and the other two active sites are wide open and exposed to solvent. The nature of the trimer configuration suggests that only one active site can be formed and be catalytically competent at a time.

  17. Chemical bonding and magnetic properties of gadolinium (Gd) substituted cobalt ferrite

    International Nuclear Information System (INIS)

    Puli, Venkata Sreenivas; Adireddy, Shiva; Ramana, C.V.

    2015-01-01

    Graphical abstract: Room temperature Raman spectra of CoFe 2−x Gd x O 4 (CFGO, x = 0.0–0.3) compounds as a function of wavenumber (cm −1 ). - Highlights: • Gd substituted ferrites were synthesized under controlled concentration. • Gd ion induced lattice dynamical changes are significant. • Enhanced magnetization is observed upon Gd-incorporation in cobalt ferrite. • A correlation between lattice dynamics and magnetic properties is established. - Abstract: Polycrystalline gadolinium (Gd) substituted cobalt ferrites (CoFe 2−x Gd x O 4 ; x = 0–0.3, referred to CFGO) ceramics have been synthesized by solid state reaction method. Chemical bonding, crystal structure and magnetic properties of CFGO compounds have been evaluated as a function of Gd-content. X-ray diffraction (XRD) and Raman spectroscopic analyses confirmed the formation of inverse spinel cubic structure. However, a secondary ortho-ferrite phase (GdFeO 3 ) nucleates for higher values of Gd-content. A considerable increase in the saturation magnetization has been observed upon the initial substitution of Gd (x = 0.1). The saturation magnetization drastically decreases at higher Gd content (x ⩾ 0.3). No contribution from ortho-ferrite GdFeO 3 phase is noted to the magnetic properties. The increase in the magnetic saturation magnetization is attributed to the higher magnetic moment of Gd 3+ (4f 7 ) residing in octahedral sites is higher when compared to that of Fe 3+ (3d 5 ) and as well due to the migration of Co 2+ (3d 7 ) ions from the octahedral to the tetrahedral sites with a magnetic moment aligned anti-parallel to those of rare earth (RE 3+ ) ions in the spinel lattice. Increase in coercivity with increase in Gd 3+ is content is attributed to magnetic anisotropy in the ceramics

  18. Nonlinear coherent structures in granular crystals

    Science.gov (United States)

    Chong, C.; Porter, Mason A.; Kevrekidis, P. G.; Daraio, C.

    2017-10-01

    The study of granular crystals, which are nonlinear metamaterials that consist of closely packed arrays of particles that interact elastically, is a vibrant area of research that combines ideas from disciplines such as materials science, nonlinear dynamics, and condensed-matter physics. Granular crystals exploit geometrical nonlinearities in their constitutive microstructure to produce properties (such as tunability and energy localization) that are not conventional to engineering materials and linear devices. In this topical review, we focus on recent experimental, computational, and theoretical results on nonlinear coherent structures in granular crystals. Such structures—which include traveling solitary waves, dispersive shock waves, and discrete breathers—have fascinating dynamics, including a diversity of both transient features and robust, long-lived patterns that emerge from broad classes of initial data. In our review, we primarily discuss phenomena in one-dimensional crystals, as most research to date has focused on such scenarios, but we also present some extensions to two-dimensional settings. Throughout the review, we highlight open problems and discuss a variety of potential engineering applications that arise from the rich dynamic response of granular crystals.

  19. Calculations of the Low-Lying Structures in the Even-Even Nd/Sm/Gd/Dy Isotopes

    Science.gov (United States)

    Lee, Su Youn; Lee, J. H.; Lee, Young Jun

    2018-05-01

    The nuclear structure of deformed nuclei has been studied using the interacting boson model (IBM). In this study, energy levels and E2 transition probabilities were determined for even nuclei in the Nd/Sm/Gd/Dy chains which have a transition characteristic between the rotational, SU(3) and vibrational, U(5) limits. The structure of the nuclei exhibits a slight breaking of the SU(3) symmetry in the direction of U(5), and therefore, we add the d-boson number operator n d , which is the main term of the U(5) symmetric Hamiltonian, to the SU(3) Hamiltonian of the IBM. The calculated results for low-lying energy levels and E2 transition rates in Nd/Sm/Gd/Dy isotopes are in reasonably good agreement with known experimental results.

  20. Structural relaxation of scintillating Ce doped NaGd(PO.sub.3./sub.).sub.4./sub. glass

    Czech Academy of Sciences Publication Activity Database

    Chromčíková, M.; Rodová, Miroslava; Nitsch, Karel; Liška, M.

    2010-01-01

    Roč. 102, č. 3 (2010), 961-964 ISSN 1388-6150 R&D Projects: GA AV ČR KAN300100802 Institutional research plan: CEZ:AV0Z10100521 Keywords : structural relaxation * Tool-Narayanaswamy-Mazurin model * thermo-mechanical analysis * Ce:NaGd(PO 3 ) 4 glass * dynamic viscosity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.752, year: 2010

  1. Solving crystal structures from neutron diffraction data

    International Nuclear Information System (INIS)

    Wilson, C.C.

    1987-07-01

    In order to pursue crystal structure determination using neutron diffraction data, and given the wide experience available of solving structures using X-ray data, the codes used in X-ray structural analysis should be adapted to the different requirements of a neutron experiment. Modifications have been made to a direct methods program MITHRIL and to a Patterson methods program PATMET to incorporate into these the features of neutron rather than X-ray diffraction. While to date these modifications have been fairly straightforward and many sophistications remain to be exploited, results obtained from the neutron versions of both programs are promising. (author)

  2. Probing structural homogeneity of La{sub 1-x}Gd{sub x}PO{sub 4} monazite-type solid solutions by combined spectroscopic and computational studies

    Energy Technology Data Exchange (ETDEWEB)

    Huittinen, N., E-mail: n.huittinen@hzdr.de [Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden (Germany); Arinicheva, Y. [Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6), 52425 Jülich (Germany); Kowalski, P.M.; Vinograd, V.L. [Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6), 52425 Jülich (Germany); JARA High-Performance Computing, Schinkelstraße 2, 52062 Aachen (Germany); Neumeier, S. [Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6), 52425 Jülich (Germany); Bosbach, D. [Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6), 52425 Jülich (Germany); JARA High-Performance Computing, Schinkelstraße 2, 52062 Aachen (Germany)

    2017-04-01

    Here we study the homogeneity of Eu{sup 3+}-doped La{sub 1-x}Gd{sub x}PO{sub 4} (x = 0, 0.11, 0.33, 0.55, 0.75, 0.92, 1) monazite-type solid solutions by a combination of Raman and time-resolved laser fluorescence spectroscopies (TRLFS) with complementary quasi-random structure-based atomistic modeling studies. For the intermediate La{sub 0.45}Gd{sub 0.55}PO{sub 4} composition we detected a significant broadening of the Raman bands corresponding to the lattice vibrations of the LnO{sub 9} polyhedron, indicating much stronger distortion of the lanthanide cation site than the PO{sub 4} tetrahedron. A distortion of the crystal lattice around the dopant site was also confirmed in our TRLFS measurements of Eu{sup 3+} doped samples, where both the half width (FWHM) of the excitation peaks and the {sup 7}F{sub 2}/{sup 7}F{sub 1} ratio derived from the emission spectra increase for intermediate solid-solution compositions. The observed variation in FWHM correlates well with the simulated distribution of Eu···O bond distances within the investigated monazites. The combined results imply that homogenous Eu{sup 3+}-doped La{sub 1-x}Gd{sub x}PO{sub 4} monazite-type solid solutions are formed over the entire composition range, which is of importance in the context of using these ceramics for immobilization of radionuclides. - Highlights: •Homogenous Eu{sup 3+}-doped La{sub 1-x}Gd{sub x}PO{sub 4} monazite-type solid solutions have been synthesized. •Solid solution formation is accompanied by slight distortion of the LnO{sub 9} polyhedron. •Raman and laser spectroscopic trends are observed within the monazite series. •Results are explained with atomistic simulations of Eu-O bond distance distribution.

  3. STREAMFINDER II: A possible fanning structure parallel to the GD-1 stream in Pan-STARRS1

    Science.gov (United States)

    Malhan, Khyati; Ibata, Rodrigo A.; Goldman, Bertrand; Martin, Nicolas F.; Magnier, Eugene; Chambers, Kenneth

    2018-05-01

    STREAMFINDER is a new algorithm that we have built to detect stellar streams in an automated and systematic way in astrophysical datasets that possess any combination of positional and kinematic information. In Paper I, we introduced the methodology and the workings of our algorithm and showed that it is capable of detecting ultra-faint and distant halo stream structures containing as few as ˜15 members (ΣG ˜ 33.6 mag arcsec-2) in the Gaia dataset. Here, we test the method with real proper motion data from the Pan-STARRS1 survey, and by selecting targets down to r0 = 18.5 mag we show that it is able to detect the GD-1 stellar stream, whereas the structure remains below a useful detection limit when using a Matched Filter technique. The radial velocity solutions provided by STREAMFINDER for GD-1 candidate members are found to be in good agreement with observations. Furthermore, our algorithm detects a ˜ {40}° long structure approximately parallel to GD-1, and which fans out from it, possibly a sign of stream-fanning due to the triaxiality of the Galactic potential. This analysis shows the promise of this method for detecting and analysing stellar streams in the upcoming Gaia DR2 catalogue.

  4. Pinning performance of (Nd,Eu,Gd)-123 superconductors: Comparison of melt-textured pellet and single crystal

    Czech Academy of Sciences Publication Activity Database

    Jirsa, Miloš; Rameš, Michal; Jurek, Karel; Muralidhar, M.; Das, P.; Koblischka, M.R.; Wolf, T.

    2008-01-01

    Roč. 151, č. 1 (2008), s. 25-30 ISSN 0921-5107 R&D Projects: GA ČR GA202/05/0173; GA MŠk 1P05ME728 Institutional research plan: CEZ:AV0Z10100520 Keywords : high-temperature superconductors * cuprous oxides * superconductivity perovskites, * (Nd,Eu,Gd)BaCuO * ternary compounds * melt-textured materials Subject RIV: BM - Solid Matter Physics ; Magnetism

  5. Crystal structure of tris(hydroxylammonium orthophosphate

    Directory of Open Access Journals (Sweden)

    Malte Leinemann

    2015-11-01

    Full Text Available The crystal structure of the title salt, ([H3NOH]+3·[PO4]3−, consists of discrete hydroxylammonium cations and orthophosphate anions. The atoms of the cation occupy general positions, whereas the anion is located on a threefold rotation axis that runs through the phosphorus atom and one of the phosphate O atoms. In the crystal structure, cations and anions are linked by intermolecular O—H...O and N—H...O hydrogen bonds into a three-dimensional network. Altogether, one very strong O—H...O, two N—H...O hydrogen bonds of medium strength and two weaker bifurcated N—H...O interactions are observed.

  6. CCDC 1416891: Experimental Crystal Structure Determination : Methyl-triphenyl-germanium

    KAUST Repository

    Bernatowicz, Piotr; Shkurenko, Aleksander; Osior, Agnieszka; Kamieński, Bohdan; Szymański, Sławomir

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  7. Multi-scale 3D characterization of long period stacking ordered structure in Mg-Zn-Gd cast alloys.

    Science.gov (United States)

    Ishida, Masahiro; Yoshioka, Satoru; Yamamoto, Tomokazu; Yasuda, Kazuhiro; Matsumura, Syo

    2014-11-01

    Magnesium alloys containing rare earth elements are attractive as lightweight structural materials due to their low density, high-specific strength and recycling efficiency. Mg-Zn-Gd system is one of promising systems because of their high creep-resistant property[1]. It is reported that the coherent precipitation formation of the 14H long period stacking ordered structure (LPSO) in Mg-Zn-Gd system at temperatures higher than 623 K[2,3]. In this study, the 14H LPSO phase formed in Mg-Zn-Gd alloys were investigated by multi-scale characterization with X-ray computer tomography (X-CT), focused ion beam (FIB) tomography and aberration-corrected STEM observation for further understanding of the LPSO formation mechanism.The Mg89.5 Zn4.5 Gd6 alloy ingots were cast using high-frequency induction heating in argon atmosphere. The specimens were aged at 753 K for 24 h in air. The aged specimen were cut and polished mechanically for microstructural analysis. The micrometer resolution X-CT observation was performed by conventional scaner (Bruker SKY- SCAN1172) at 80 kV. The FIB tomography and energy dispersive x-ray spectroscopy (EDS) were carried out by a dual beam FIB-SEM system (Hitachi MI-4000L) with silicon drift detector (SDD) (Oxford X-Max(N)). The electron acceleration voltages were used with 3 kV for SEM observation and 10 kV for EDX spectroscopy. The 3D reconstruction from image series was performed by Avizo Fire 8.0 software (FEI). TEM/STEM observations were also performed by transmission electron microscopes (JEOL JEM 2100, JEM-ARM 200F) at the acceleration voltage of 200 keV.The LPSO phase was observed clearly in SEM image of the Mg89.5Zn4.5Gd6 alloy at 753 K for 2h (Fig.1 (a)). The atomic structure of LPSO phase observed as white gray region of SEM image was also confirmed as 14H LPSO structure by using selected electron diffraction patterns and high-resolution STEM observations. The elemental composition of LPSO phase was determined as Mg97Zn1Gd2 by EDS analyses

  8. First measurement of the nonlinear coefficient for Gd1-xLux Ca4O(BO3)3 and Gd1-xScxCa4O(BO3)3 crystals

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Mortensen, Jesper Liltorp; Germershausen, Sven

    2007-01-01

    The effective nonlinear coefficient and temperature acceptance bandwidth of three Lu and Sc co-doped GdCa4O(B03)3 type nonlinear crystals were measured. NCPM for SHG in to the blue-UV spectral region can be obtained by controlling the co-dopant concentration. Measurements were based on intra-cavi...

  9. Optically induced structural phase transitions in ion Coulomb crystals

    DEFF Research Database (Denmark)

    Horak, Peter; Dantan, Aurelien Romain; Drewsen, Michael

    2012-01-01

    We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures, such as b......We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures...

  10. Analysis on the energetics, magnetism and electronic properties in a 45° ZnO grain boundary doped with Gd

    KAUST Repository

    Devi, Assa Aravindh Sasikala

    2018-04-13

    The structural stability and magnetic properties of a grain boundary (GB) formed by aligning two ZnO single crystals oriented at an angle of 45° is investigated by density functional theory, using generalized gradient approximation (GGA) and taking the U parameter into consideration for the 4f impurity states. We found that the GB is stable with no dangling bonds and inter-granular structures. The stability of defects such as Gd substituted to the Zn site (Gd), Zn vacancy (V) and O vacancy (V) as well as defect complexes Gd-Gd, Gd-V, and Gd-V are analyzed using formation energy calculations. It is found that Gd-Gd clusters prefers to form at the GB. The spin polarization at the Gd sites is too localized and the exchange coupling energy is insufficient to overcome the thermal fluctuations. However, we show that the presence of V increases the hybridization between p orbitals of O as well as d orbitals of Zn, which can assist in increasing the magnetic polarization of the system. This work advances the understanding of the ferromagnetism in Gd-doped ZnO, indicating that Gd clustering at the GB is not likely to contribute to the ferromagnetism.

  11. Detailed crystallization study of co-precipitated Y1.47 Gd1.53 Fe5 O12 and relevant magnetic properties

    International Nuclear Information System (INIS)

    Serra, Rogerio Arving; Ogasawara, Tsuneharu; Ogasawara, Angelica Soares

    2007-01-01

    The crystallization process of co-precipitated Y 1.5 Gd 1.5 Fe 5 O 12 powder heated up to 1000 deg C at rate of 5 deg C min -1 was investigated. Above 810 deg C crystalline Y 1.47 Gd 1.53 Fe 5 O 12 was obtained with a lattice parameter of 12.41 A and a theoretical density of 5.84 g cm -3 . Dry pressed rings were sintered at 1270 and 1320 deg C, increasing the grain-size from 3.1 to 6.5 μm, the theoretical density by 87.6 to 95.3% and decreasing H c from 2.9725 to 1.4005 Oe. Additionally, Hc increased when the frequency of the hysteresis graph varied from 60 Hz to 10 kHz, the curie temperature was 282.4 deg C and Ms equalled 9.25 emu g -1 (0.17 kG) agreeing well with the B s -value of the hysteresis graph and literature values. (author)

  12. Glass-ceramic nuclear waste forms obtained by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

    Science.gov (United States)

    Loiseau, P.; Caurant, D.

    2010-07-01

    Glass-ceramic materials containing zirconolite (nominally CaZrTi 2O 7) crystals in their bulk can be envisaged as potential waste forms for minor actinides (Np, Am, Cm) and Pu immobilization. In this study such matrices are synthesized by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th) as surrogates. A thin partially crystallized layer containing titanite and anorthite (nominally CaTiSiO 5 and CaAl 2Si 2O 8, respectively) growing from glass surface is also observed. The effect of the nature and concentration of surrogates on the structure, the microstructure and the composition of the crystals formed in the surface layer is presented in this paper. Titanite is the only crystalline phase able to significantly incorporate trivalent lanthanides whereas ThO 2 precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 °C) is shown to strongly affect glass-ceramics microstructure. For the system studied in this paper, it appears that zirconolite is not thermodynamically stable in comparison with titanite growing form glass surface. Nevertheless, for kinetic reasons, such transformation (i.e. zirconolite disappearance to the benefit of titanite) is not expected to occur during interim storage and disposal of the glass-ceramic waste forms because their temperature will never exceed a few hundred degrees.

  13. Recent experiments at Brookhaven: level structure of N = 86 isotones 156Yb and 150Gd

    International Nuclear Information System (INIS)

    Sunyar, A.W.

    1980-01-01

    States of the N = 86 isotones 156 Yb and 150 Gd have been studied by means of the 144 Sm( 16 O,4n) 156 Yb, 113 In( 46 Ti,p2n) 156 Yb, and 124 Sn( 30 Si,4n) 150 Gd reactions. Levels have been established to spin 36 h-bar and over 12.5 MeV in excitation in 150 Gd and to beyond spin 25 h-bar in 156 Yb. The systematics of levels in the N = 86 isotones from 150 Gd to 156 Yb are described, and the near-spherical shell model description for states in this region to near spin 30 h-bar is discussed. A T/sub 1/2/ = 6 ns, 72-keV isomeric transition in 156 Yb has been discovered, and an E1 multipolarity is assigned to this transition. The spin-parity of the isomeric state is established as 11 - . 6 figures

  14. Structural and optical characteristics of Ce, Nd, Gd, and Dy-doped ...

    Indian Academy of Sciences (India)

    Ashwini S Varpe

    2017-06-19

    Jun 19, 2017 ... Al2O3-Gd. Al2O3-Dy. Figure 2. XRD patterns of RE:Al2O3 thin films for 5 mol% concentration of RE elements ... is due to more segregation of Ce3+ ions along the grain ..... to the split ground state into their 2F7/2 and 2F5/2.

  15. Crystal structure of natural phaeosphaeride A

    Directory of Open Access Journals (Sweden)

    Victoria V. Abzianidze

    2015-08-01

    Full Text Available The asymmetric unit of the title compound, C15H23NO5, contains two independent molecules. Phaeosphaeride A contains two primary sections, an alkyl chain consisting of five C atoms and a cyclic system consisting of fused five- and six-membered rings with attached substituents. In the crystal, the molecules form layered structures. Nearly planar sheets, parallel to the (001 plane, form bilayers of two-dimensional hydrogen-bonded networks with the hydroxy groups located on the interior of the bilayer sheets. The network is constructed primarily of four O—H...O hydrogen bonds, which form a zigzag pattern in the (001 plane. The butyl chains interdigitate with the butyl chains on adjacent sheets. The crystal was twinned by a twofold rotation about the c axis, with refined major–minor occupancy fractions of 0.718 (6:0.282 (6.

  16. Diode-laser-pumped high efficiency continuous-wave operation at 912 nm laser in Nd:GdVO4 crystal

    International Nuclear Information System (INIS)

    Yu, X; Chen, F; Gao, J; Li, X D; Yan, R P; Zhang, K; Yu, J H; Zhang, Z H

    2009-01-01

    High efficiency operation on continuous-wave (cw) 912 nm laser at room temperature in Nd:GdVO 4 crystal pumped by 808 nm diode-laser is reported in this letter. The maximum output power of 8.0 W was obtained at the incident un-polarized pump power of 47.0 W, giving the corresponding optical-to-optical conversion efficiency of 17.0% and the average slope efficiency of 22.9%. Further tests show that the lasing threshold is reduced and the efficiency is increased evidently when using the π-polarized 808 nm pump source. 4.8 W 912 nm laser was achieved at the polarized pump power of 21.8 W, optical-to-optical conversion efficiency is increased to 22.0% and average slope efficiency is up to 33.6%

  17. 926 nm laser operation in Nd:GdNbO4 crystal based on 4F3/2 → 4I9/2 transition

    Science.gov (United States)

    Yan, Renpeng; Li, Xudong; Yao, Wenming; Shen, Yingjie; Zhou, Zhongxiang; Peng, Fang; Zhang, Qingli; Dou, Renqing; Gao, Jing

    2018-05-01

    926 nm laser operation in a Nd:GdNbO4 crystal based on quasi-three-level 4F3/2 → 4I9/2 transition is reported, for the first time to our best knowledge. An average output power of 393 mW at 926 nm under 879 nm LD pumping is obtained with a slope efficiency of 33.3% and an optical-to-optical efficiency of 26.0%. The slope efficiency with respect to absorbed pump power is estimated to be 47.7%. Comparison between output characters of 926 nm laser under direct and indirect pumping is conducted. The average output power at 926 nm under 808 nm LD pumping reaches 305 mW with an optical-to-optical efficiency of 16.1%.

  18. Efficient infrared (≈1.9-2.0 μm) laser operation in color-defect-free Tm:NaGd(MoO4)2 crystal

    Science.gov (United States)

    Han, X.; Rico, M.; Serrano, M. D.; Cascales, C.; Zaldo, C.

    2013-04-01

    Color-defect-free 5 at.% Tm:NaGd(MoO4)2 crystals have been grown in a Na2MoO4/Na2Mo2O7 flux. Using a hemispherical optical cavity and pumping at λ = 794.5 nm with a Ti-sapphire laser, up to 850 mW of output power at λ ≈ 1900 nm was obtained at 300 K with an output coupler transmission of 8%. In the cw regime, the slope efficiency versus absorbed power was η = 45% and the pump power laser threshold was ≈180 mW. The laser was tunable from 1875 to 1975 nm and the emission had a FWHM bandwidth ≈20 nm, indicating the potential for ultrashort laser pulse generation.

  19. Electronic structure and metallization of cubic GdH{sub 3} under pressure: Ab initio many-body GW calculations

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Bo, E-mail: kong79@yeah.net, E-mail: yachao.zhang@pku.edu.cn [School of Physics and Electronic Sciences, Guizhou Education University, Guiyang 550018 (China); Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang 550018 (China); Zhang, Yachao, E-mail: kong79@yeah.net, E-mail: yachao.zhang@pku.edu.cn [Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang 550018 (China)

    2016-07-07

    The electronic structures of the cubic GdH{sub 3} are extensively investigated using the ab initio many-body GW calculations treating the Gd 4f electrons either in the core (4f-core) or in the valence states (4f-val). Different degrees of quasiparticle (QP) self-consistent calculations with the different starting points are used to correct the failures of the GGA/GGA + U/HSE03 calculations. In the 4f-core case, GGA + G{sub 0}W{sub 0} calculations give a fundamental band gap of 1.72 eV, while GGA+ GW{sub 0} or GGA + GW calculations present a larger band gap. In the 4f-val case, the nonlocal exchange-correlation (xc) functional HSE03 can account much better for the strong localization of the 4f states than the semilocal or Hubbard U corrected xc functional in the Kohn–Sham equation. We show that the fundamental gap of the antiferromagnetic (AFM) or ferromagnetic (FM) GdH{sub 3} can be opened up by solving the QP equation with improved starting point of eigenvalues and wave functions given by HSE03. The HSE03 + G{sub 0}W{sub 0} calculations present a fundamental band gap of 2.73 eV in the AFM configuration, and the results of the corresponding GW{sub 0} and GW calculations are 2.89 and 3.03 eV, respectively. In general, for the cubic structure, the fundamental gap from G{sub 0}W{sub 0} calculations in the 4f-core case is the closest to the real result. By G{sub 0}W{sub 0} calculations in the 4f-core case, we find that H or Gd defects can strongly affect the band structure, especially the H defects. We explain the mechanism in terms of the possible electron correlation on the hydrogen site. Under compression, the insulator-to-metal transition in the cubic GdH{sub 3} occurs around 40 GPa, which might be a satisfied prediction.

  20. A new ~1 μm laser crystal Nd:Gd2SrAl2O7: growth, thermal, spectral and lasing properties

    Science.gov (United States)

    Yuan, Feifei; Liao, Wenbin; Huang, Yisheng; Zhang, Lizhen; Sun, Shijia; Wang, Yeqing; Lin, Zhoubin; Wang, Guofu; Zhang, Ge

    2018-03-01

    Nd:Gd2SrAl2O7 crystals were grown by the Czochralski technique; thermal, spectral and laser properties were investigated in detail. The average thermal expansion coefficients along a- and c-axis are 12.6  ×  10-6 K-1 and 14.9  ×  10-6 K-1, respectively. At room temperature, the thermal conductivities are 4.98 and 5.24 W (m-1 * K-1) along the a- and c-axis, respectively. The absorption cross sections at ~808 nm are 13.7  ×  10-20 cm2 with a FWHM of 3.3 nm for π-polarization and 11.84  ×  10-20 cm2 with a FWHM of 3.4 nm for σ-polarization. The emission cross sections at ~1080 nm are 15  ×  10-20 cm2 and 12.7  ×  10-20 cm2 with a FWHM of about 5.1 nm and 12.5 nm for π- and σ-polarization, respectively. The fluorescence lifetime for the 4F3/2  →  4I11/2 transition was fitted to be 118 µs. Pumped by a fiber-coupled 808 nm laser diode, the maximum 1.55 W continuous-wave laser output at ~1.08 µm was achieved with a slope efficiency of 30.5%. All the results show that Nd:Gd2SrAl2O7 crystal is a promising laser material.

  1. Crystal structure of Cryptosporidium parvum pyruvate kinase.

    Directory of Open Access Journals (Sweden)

    William J Cook

    Full Text Available Pyruvate kinase plays a critical role in cellular metabolism of glucose by serving as a major regulator of glycolysis. This tetrameric enzyme is allosterically regulated by different effector molecules, mainly phosphosugars. In response to binding of effector molecules and substrates, significant structural changes have been identified in various pyruvate kinase structures. Pyruvate kinase of Cryptosporidium parvum is exceptional among known enzymes of protozoan origin in that it exhibits no allosteric property in the presence of commonly known effector molecules. The crystal structure of pyruvate kinase from C. parvum has been solved by molecular replacement techniques and refined to 2.5 Å resolution. In the active site a glycerol molecule is located near the γ-phosphate site of ATP, and the protein structure displays a partially closed active site. However, unlike other structures where the active site is closed, the α6' helix in C. parvum pyruvate kinase unwinds and assumes an extended conformation. In the crystal structure a sulfate ion is found at a site that is occupied by a phosphate of the effector molecule in many pyruvate kinase structures. A new feature of the C. parvum pyruvate kinase structure is the presence of a disulfide bond cross-linking the two monomers in the asymmetric unit. The disulfide bond is formed between cysteine residue 26 in the short N-helix of one monomer with cysteine residue 312 in a long helix (residues 303-320 of the second monomer at the interface of these monomers. Both cysteine residues are unique to C. parvum, and the disulfide bond remained intact in a reduced environment. However, the significance of this bond, if any, remains unknown at this time.

  2. Crystal structure of MboIIA methyltransferase.

    Science.gov (United States)

    Osipiuk, Jerzy; Walsh, Martin A; Joachimiak, Andrzej

    2003-09-15

    DNA methyltransferases (MTases) are sequence-specific enzymes which transfer a methyl group from S-adenosyl-L-methionine (AdoMet) to the amino group of either cytosine or adenine within a recognized DNA sequence. Methylation of a base in a specific DNA sequence protects DNA from nucleolytic cleavage by restriction enzymes recognizing the same DNA sequence. We have determined at 1.74 A resolution the crystal structure of a beta-class DNA MTase MboIIA (M.MboIIA) from the bacterium Moraxella bovis, the smallest DNA MTase determined to date. M.MboIIA methylates the 3' adenine of the pentanucleotide sequence 5'-GAAGA-3'. The protein crystallizes with two molecules in the asymmetric unit which we propose to resemble the dimer when M.MboIIA is not bound to DNA. The overall structure of the enzyme closely resembles that of M.RsrI. However, the cofactor-binding pocket in M.MboIIA forms a closed structure which is in contrast to the open-form structures of other known MTases.

  3. Pulse shape discrimination properties of Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12}:Ce,B single crystal in comparison with CsI:Tl

    Energy Technology Data Exchange (ETDEWEB)

    Rawat, S. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Department of Physics, Indian Institute of Technology, Roorkee 247667 (India); Tyagi, Mohit [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Netrakanti, P.K.; Kashyap, V.K.S.; Mitra, A. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Singh, A.K.; Desai, D.G. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kumar, G. Anil [Department of Physics, Indian Institute of Technology, Roorkee 247667 (India); Gadkari, S.C. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2016-12-21

    Single crystals of Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12}:Ce,B and CsI:Tl were grown by Czochralski and Bridgman techniques, respectively. While both the crystals exhibited similar emission at about 550 nm, their scintillation decay times showed significantly different characteristics. The average scintillation decay time of Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12}:Ce,B crystal was found to be about 284 ns for alpha excitation compared to 108 ns measured for a gamma source. On the other hand in CsI:Tl crystals, the alpha excitation resulted in a lower average decay time of 600 ns compared to 1200 ns with gamma excitation. Their pulse shape discrimination (PSD) for gamma and alpha radiations were studied by coupling the scintillators with photomultiplier tube or SiPM and employing an advanced digitizer as well as a conventional zero-crossing setup. In spite of having a poor α/γ light yield ratio, the PSD figure of merit and the difference of zero-crossing time in Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12}:Ce,B crystals were found to be superior in comparison to CsI:Tl crystals.

  4. Polymorphous GdScO3 as high permittivity dielectric

    International Nuclear Information System (INIS)

    Schäfer, A.; Rahmanizadeh, K.; Bihlmayer, G.; Luysberg, M.; Wendt, F.; Besmehn, A.; Fox, A.

    2015-01-01

    Four different polymorphs of GdScO 3 are assessed theoretically and experimentally with respect to their suitability as a dielectric. The calculations carried out by density functional theory reveal lattice constants, band gaps and the energies of formation of three crystal phases. Experimentally all three crystal phases and the amorphous phase can be realized as thin films by pulsed laser deposition using various growth templates. Their respective crystal structures are confirmed by X-ray diffraction and transmission electron microscopy reflecting the calculated lattice constants. X-ray photoelectron spectroscopy unveils the band gaps of the different polymorphs of GdScO 3 which are above 5 eV for all films demonstrating good insulating properties. From capacitance voltage measurements, high permittivities of up to 27 for hexagonal GdScO 3 are deduced. - Highlights: • Different epitaxial polymorph phases of GdScO 3 were grown by pulsed laser deposition. • The cubic phase of GdScO 3 is reported for the first time. • All phases are proven to be useful for the use in silicon based and III–V based microelectronic devices.

  5. Crystal Structure of the 30S Ribosomal Subunit from Thermus Thermophilus: Purification, Crystallization and Structure Determination

    International Nuclear Information System (INIS)

    Clemons, William M. Jr.; Brodersen, Ditlev E.; McCutcheonn, John P.; May, Joanna L.C.; Carter, Andrew P.; Morgan-Warren, Robert J.; Wimberly, Brian T.; Ramakrishnan, Venki

    2001-01-01

    We describe the crystallization and structure determination of the 30 S ribosomal subunit from Thermus thermophilus. Previous reports of crystals that diffracted to 10 (angstrom) resolution were used as a starting point to improve the quality of the diffraction. Eventually, ideas such as the addition of substrates or factors to eliminate conformational heterogeneity proved less important than attention to detail in yielding crystals that diffracted beyond 3 (angstrom) resolution. Despite improvements in technology and methodology in the last decade, the structure determination of the 30 S subunit presented some very challenging technical problems because of the size of the asymmetric unit, crystal variability and sensitivity to radiation damage. Some steps that were useful for determination of the atomic structure were: the use of anomalous scattering from the LIII edges of osmium and lutetium to obtain the necessary phasing signal; the use of tunable, third-generation synchrotron sources to obtain data of reasonable quality at high resolution; collection of derivative data precisely about a mirror plane to preserve small anomalous differences between Bijvoet mates despite extensive radiation damage and multi-crystal scaling; the pre-screening of crystals to ensure quality, isomorphism and the efficient use of scarce third-generation synchrotron time; pre-incubation of crystals in cobalt hexaammine to ensure isomorphism with other derivatives; and finally, the placement of proteins whose structures had been previously solved in isolation, in conjunction with biochemical data on protein-RNA interactions, to map out the architecture of the 30 S subunit prior to the construction of a detailed atomic-resolution model.

  6. Gadolinium scandium germanide, Gd2Sc3Ge4

    Directory of Open Access Journals (Sweden)

    Sumohan Misra

    2009-04-01

    Full Text Available Gd2Sc3Ge4 adopts the orthorhombic Pu5Rh4-type structure. The crystal structure contains six sites in the asymmetric unit: two sites are statistically occupied by rare-earth atoms with Gd:Sc ratios of 0.967 (4:0.033 (4 and 0.031 (3:0.969 (3, one site (.m. symmetry is occupied by Sc atoms, and three distinct sites (two of which with .m. symmetry are occupied by Ge atoms. The rare-earth atoms form two-dimensional slabs with Ge atoms occupying the trigonal-prismatic voids.

  7. Synthesis, electronic structure and luminescent properties of a new red-emitting phosphor GdBiW2O9:Eu3+

    Science.gov (United States)

    Xie, Zhi; Zhou, Weiwei; Zhao, Wang; Zhang, Hao; Hu, Qichang; Xu, Xuee

    2017-10-01

    Red phosphor of GdBiW2O9:Eu3+ was prepared by solid-state reaction method. The phase purity and structure of the samples were characterized by XRD. The electronic structures of GdBiW2O9 host were estimated by DFT calculation. The PLE and PL spectra were also investigated. The optimal luminescent properties of GdBiW2O9:Eu3+ phosphors were obtained at 900 °C with 40 mol% of Eu3+ concentration. The phosphors can be excited efficiently by 396 nm NUV light and emit intense red light peaking at 618 nm. The results indicate GdBiW2O9:Eu3+ can act as a potential red-emitting phosphor for LEDs application.

  8. Accuracy of crystal structure error estimates

    International Nuclear Information System (INIS)

    Taylor, R.; Kennard, O.

    1986-01-01

    A statistical analysis of 100 crystal structures retrieved from the Cambridge Structural Database is reported. Each structure has been determined independently by two different research groups. Comparison of the independent results leads to the following conclusions: (a) The e.s.d.'s of non-hydrogen-atom positional parameters are almost invariably too small. Typically, they are underestimated by a factor of 1.4-1.45. (b) The extent to which e.s.d.'s are underestimated varies significantly from structure to structure and from atom to atom within a structure. (c) Errors in the positional parameters of atoms belonging to the same chemical residue tend to be positively correlated. (d) The e.s.d.'s of heavy-atom positions are less reliable than those of light-atom positions. (e) Experimental errors in atomic positional parameters are normally, or approximately normally, distributed. (f) The e.s.d.'s of cell parameters are grossly underestimated, by an average factor of about 5 for cell lengths and 2.5 for cell angles. There is marginal evidence that the accuracy of atomic-coordinate e.s.d.'s also depends on diffractometer geometry, refinement procedure, whether or not the structure has a centre of symmetry, and the degree of precision attained in the structure determination. (orig.)

  9. The Crystal Structures of Potentially Tautomeric Compounds

    Science.gov (United States)

    Furmanova, Nina G.

    1981-08-01

    Data on the structures of potentially proto-, metallo-, and carbono-tropic compounds, obtained mainly by X-ray diffraction, are surveyed. The results of neutron and electron diffraction studies have also been partly used. It is shown that a characteristic feature of all the systems considered is the formation of hydrogen or secondary bonds ensuring the contribution of both possible tautomeric forms to the structure. Systematic consideration of the experimental data leads to the conclusion that there is a close relation between the crystal structure and the dynamic behaviour of the molecules in solution and that secondary and hydrogen bonds play a significant role in the tautomeric transition. The bibliography includes 152 references.

  10. Novel Crystal Structure C60 Nanowire

    Science.gov (United States)

    Mickelson, William; Aloni, Shaul; Han, Weiqiang; Cumings, John; Zettl, Alex

    2003-03-01

    We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride (BN) nanotubes. For small-diameter BN tubes, the wire consists of a linear chain of C60's. With increasing BN tube inner diameter, novel C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) which are unknown for bulk or thin film forms of C60. C60 in BN nanotubes presents a model system for studying the properties of new dimensionally-constrained "silo" crystal structures.

  11. Crystal structure of MboIIA methyltransferase

    OpenAIRE

    Osipiuk, Jerzy; Walsh, Martin A.; Joachimiak, Andrzej

    2003-01-01

    DNA methyltransferases (MTases) are sequence-specific enzymes which transfer a methyl group from S-adenosyl-l-methionine (AdoMet) to the amino group of either cytosine or adenine within a recognized DNA sequence. Methylation of a base in a specific DNA sequence protects DNA from nucleolytic cleavage by restriction enzymes recognizing the same DNA sequence. We have determined at 1.74 Å resolution the crystal structure of a β-class DNA MTase MboIIA (M·MboIIA) from the bacterium Moraxella bovis,...

  12. Structure and magnetism in Fe-Gd based dinuclear and chain systems: the interplay of weak exchange coupling and zero field splitting effects

    NARCIS (Netherlands)

    Ferbinteanu, M.; Cimpoesu, F.; Gîrtu, M. A.; Enachescu, C.; Tanase, S.

    2012-01-01

    The synthesis and characterization of two Fe-Gd systems based on bpca- (Hbpca = bis(2-pyridilcarbonyl)amine) as bridging ligand is presented, taking the systems as a case study for structure-property correlations. Compound 1, [FeLSII(μ-bpca)2Gd(NO3)2(H2O)]NO3·2CH3NO2, is a zigzag polymer,

  13. Crystal phase transition in LixNa1-xGdF4 solid solution nanocrystals - Tuning of optical properties

    KAUST Repository

    Bański, Mateusz; Afzaal, Mohammad; Cha, Dong Kyu; Wang, X.; Tan, Hua; Misiewicz, Jan J.; Podhorodecki, Artur P.

    2014-01-01

    field symmetry and emission properties from doped europium (Eu3+) ions. We report that for lithium (Li+) substitution <15%, the hexagonal crystal field is preferred, while the Eu3+ emission is already tuned, whereas at higher Li+ substitution, a phase

  14. Crystal and molecular structure of 2-thiouridine

    Energy Technology Data Exchange (ETDEWEB)

    Hawkinson, S W

    1977-01-01

    The ''minor'' nucleoside 2-thiouridine, C/sub 9/H/sub 12/O/sub 5/N/sub 2/S, crystallizes in a monoclinic cell, space group P2/sub 1/ with a = 5.049 (2), b = 7.526 (2), c = 14.050 (3) A, ..beta.. = 90.17 (2)/sup 0/, and d = 1.619 g cm/sup -3/ (for Z = 2) at 22 +- 2/sup 0/C. The structure was derived from 1334 unique intensities measured with an Oak Ridge computer-controlled diffractometer to a limit of sin theta/lambda = 0.65 A/sup -1/ with Nb-filtered Mo K..cap alpha.. radiation. Atomic parameters were obtained by a combination of Patterson and Fourier techniques and refined by full-matrix least squares to a final R(F) value of 0.023 for all data. The bond lengths and angles in the molecule agree well with those of other thiopyrimidines (C(2) - S = 1.677 A). The conformation of the sugar ring relative to the base is anti with a torsion angle chi(O(1')--C(1') ..-->.. N(1)--C(6)) of 17/sup 0/. The sugar exists in the 3'-endo conformation. The O(5')--C(5') bond is gauche to C(4) - O(1') and trans to C(4')--C(3') (torsion angles of 74 and -169/sup 0/ respectively). The molecules are linked together in the crystal by hydrogen bonds in an intricate network which is identical to that inferred by Kojic-Prodic, Liminga, Sljukic and Ruzic-Toros (Acta Cryst. (1974), B30, 1550-1555) for the crystal structure of 5,6-dihydro-2-thiouridine. 2 figures; 6 tables.

  15. Glass formation ability, structure and magnetocaloric effect of a heavy rare-earth bulk metallic glassy Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Jo, C.-L. [Shanghai University, School of Materials Science and Engineering, Yanchang Road 149, Zhabei District, 200072 Shanghai (China)], E-mail: jochollong@163.com; Xia Lei; Ding Ding; Dong Yuanda; Gracien, Ekoko [Shanghai University, School of Materials Science and Engineering, Yanchang Road 149, Zhabei District, 200072 Shanghai (China)

    2008-06-30

    The glass formation ability, the structure and the magnetocaloric effect of the bulk metallic glassy Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy were investigated. Bulk metallic glassy (BMGs) alloys were prepared by a copper-mold casting method. The glass forming ability and their structure were studied by using X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The XRD analysis revealed that the as-cast cylinder of Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy showed fully amorphous structure in 2 mm diameter. The DSC revealed that the bulk cylinder of the Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy showed a distinct glass transition temperature and a relatively wide supercooled liquid region before crystallization. SQUID investigated the magnetic properties and the entropy changes. The Curie temperature of Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} BMGs alloy was about 130 K, but the maximum magnetic entropy changes(-{delta}S{sub M}) showed at about 125 K, a little lower than the Curie temperature 130 K. The reason could probably be due to the presence of a little amount of nanocrystalline particles between amorphous phases. The BMG alloy has the characteristic of second-order transition (SOT) on Arrott plots. The results showed that the amorphous sample had a relatively improved magnetocaloric effect, indicating that the amorphous alloy could be considered as a candidate for magnetic refrigeration applications in the temperature interval range of 100-200 K.

  16. Structure and Chemical Bonding of the Li-Doped Polar Intermetallic RE2In1−xLixGe2 (RE = La, Nd, Sm, Gd; x = 0.13, 0.28, 0.43, 0.53 System

    Directory of Open Access Journals (Sweden)

    Junsu Lee

    2018-03-01

    Full Text Available Four polar intermetallic compounds belonging to the RE2In1−xLixGe2 (RE = La, Nd, Sm, Gd; x = 0.13(1, 0.28(1, 0.43(1, 0.53(1 system have been synthesized by the traditional solid-state reaction method, and their crystal structures have been characterized by single-crystal X-ray diffraction (SXRD analyses. The isotypic crystal structures of four title compounds adopt the Mo2FeB2-type structure having the tetragonal space group P4/mbm (Z = 2, Pearson code tP40 with three crystallographically independent atomic sites and can be simply described as a pile of the identical 2-dimensioanl (2D RE2In1-xLixGe2 slabs stacked along the c-axis direction. The substituting Li atom shows a particular site preference for replacing In at the Wyckoff 2a site rather than Ge at the Wyckoff 4g in this crystal structure. As the size of a used rare-earth metal decreases from La3+ to Gd3+ throughout the title system, the Ge-Ge and Ge-In/Li bond distances, both of which consist of the 2D anionic Ge2(In/Li layer, gradually decrease resulting in the reduction of a unit cell volume. A series of theoretical investigations has been performed using a hypothetical structure model Gd2In0.5Li0.5Ge2 by tight-binding linear muffin-tin orbital (TB-LMTO method. The resultant densities of states (DOS value at the Fermi level (EF suggests a metallic conductivity for this particular composition, and this calculation result is in a good agreement with the formal charge distribution assigning two extra valence electrons for a metal-metal bond in the conduction band. The thorough analyses of six crystal orbital Hamilton population (COHP curves representing various interatomic interactions and an electron localization function (ELF diagram indicating the locations of paired-electron densities are also provided in this article.

  17. Ab initio molecular dynamics simulation of the liquid and amorphous structure of Mg65Cu25Gd10 alloy

    International Nuclear Information System (INIS)

    Gao, R.; Zhao, Y.F.; Liu, X.J.; Liu, Z.K.; Hui, X.

    2013-01-01

    The liquid and amorphous structures of Mg 65 Cu 25 Gd 10 alloy were studied by using molecular dynamics methods within the frame of density functional theory. The generalized and partial pair correlation functions, structure factors, coordination numbers and bond pairs for this alloy were analyzed. It is shown that this alloy exhibit typical characterization of liquid structure at the temperature higher than 750 K, and of amorphous structure with shoulders on the second diffuse peaks of the pair correlation functions curves at room temperature. The local short and medium range ordering tends to be increased with the decrease of temperature. Both the liquid and the amorphous structures are mainly composed of icosahedral type of bond pairs. Perfect and distorted icosahedra can be differentiated from the atomic configuration of the amorphous alloy

  18. Syntheses and Crystal Structures of Ferrocenoindenes

    Directory of Open Access Journals (Sweden)

    Gerhard Laus

    2013-02-01

    Full Text Available Ferrocenoindenes display planar chirality and thus represent valuable ligands for asymmetric catalysis. Here, we report on the synthesis of novel 3-(1,1-dibromomethyleneferroceno[1,2-a]indene, (Z-3-(1-bromomethylene-6-iodoferroceno[1,2-a]indene, and benzo[5,6-f]ferroceno[2,3,a]inden-1-one. Any application-oriented design of chiral catalysts requires fundamental knowledge about the ligands involved, not only in terms of atom-connectivity, but also in terms of their three-dimensional structure and steric demand. Therefore, the crystal structures of 2-ferrocenylbenzoic acid, ferroceno[1,2-a]indene, and (Z-3-(1-bromomethylene-6-iodoferroceno[1,2-a]indene have been determined. The bond-lengths that can be retrieved therefrom also allow for an estimation of the reactivity of the aryl-iodo, bromo-methylidene and dibromomethylidene moieties.

  19. The crystal structure of scandium dyhydrate triglycolate

    International Nuclear Information System (INIS)

    Dukareva, L.M.; Antishkina, A.S.; Porai-Koshits, M.A.; Ostrikova, V.N.; Arkhangel'skij, I.V.; Amanov, A.Z.

    1978-01-01

    The structure of colorless crystals of scandium glycolate dehydrate Sc(CH 2 OHCOO) 3 x2H 2 O, synthesized at the chemical department of MSU has been investigated. Parameters of the monoclinic lattice are determined according to roentgenograms of swing and Kforograms and are specified using the DRON-1 diffractor: a=14.624-+0.005 A; b=13.052-+0.003 A; c=5.730+-0.003 A; γ=96.26 deg+-0.01 deg; rhosub(exper.)=1.09 g/cm 3 ; Z=4; Sp.=P 2/b. Experimental photographic data are obtained using the KFOR chamber. Scannings of the layer lines h anti Ko-h anti K4, containing 742 independent reflexes are taken. Deciphering of the structure is carried out by means of analysis of the Paterson functions distribution and conventional and differential electron densities. Description of the system is presented

  20. Structure, thermodynamics, and crystallization of amorphous hafnia

    International Nuclear Information System (INIS)

    Luo, Xuhui; Demkov, Alexander A.

    2015-01-01

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO 2 . The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia

  1. The Crystal Structures of Two Novel Cadmium-Picolinic Acid ...

    African Journals Online (AJOL)

    The crystal structures of two novel cadmium-picolinic acid complexes grown in aqueous solutions at selected pH values are reported. The structures are compared to expected solution species under the same conditions. The crystal structure of complex 1 exhibits a seven coordinate structure which contains a protonated ...

  2. EPR spectroscopy of MRI-related Gd(III) complexes: simultaneous analysis of multiple frequency and temperature spectra, including static and transient crystal field effects.

    Science.gov (United States)

    Rast, S; Borel, A; Helm, L; Belorizky, E; Fries, P H; Merbach, A E

    2001-03-21

    For the first time, a very general theoretical method is proposed to interpret the full electron paramagnetic resonance (EPR) spectra at multiple temperatures and frequencies in the important case of S-state metal ions complexed in liquid solution. This method is illustrated by a careful analysis of the measured spectra of two Gd3+ (S = 7/2) complexes. It is shown that the electronic relaxation mechanisms at the origin of the EPR line shape arise from the combined effects of the modulation of the static crystal field by the random Brownian rotation of the complex and of the transient zero-field splitting. A detailed study of the static crystal field mechanism shows that, contrarily to the usual global models involving only second-order terms, the fourth and sixth order terms can play a non-negligible role. The obtained parameters are well interpreted in the framework of the physics of the various underlying relaxation processes. A better understanding of these mechanisms is highly valuable since they partly control the efficiency of paramagnetic metal ions in contrast agents for medical magnetic resonance imaging (MRI).

  3. Angular non-critical phase-matching second-harmonic-generation characteristics of RECOB (RE = Tm, Y, Gd, Sm, Nd and La) crystals.

    Science.gov (United States)

    Liu, Yanqing; Wang, Zhengping; Yu, Fapeng; Qi, Hongwei; Yang, Xiuqin; Yu, Xiaoqiang; Zhao, Xian; Xu, Xinguang

    2017-05-15

    For the first time, the angular non-critical phase-matching (A-NCPM) second-harmonic-generation (SHG) characteristics of a family of monoclinic oxoborate crystals, RECa 4 O(BO 3 ) 3 (RECOB, RE = Tm, Y, Gd, Sm, Nd and La), were comprehensively investigated. For all of the realizable A-NCPM SHG styles, the feature parameters including PM wavelength, angular, wavelength and temperature acceptance bandwidths, have been derived from the theory and verified by the experiments. We discovered that the closer the ion radius between RE 3+ and Ca 2+ , the smaller the birefringence, and the better the A-NCPM SHG properties. As a result, for the Type-I SHG on Y-axis which has the largest effective nonlinear optical coefficient (d eff ) among the three realizable A-NCPM styles, NdCOB crystal presents the longest PM wavelength (927 nm), the largest angular acceptance bandwidth (Δθ⋅l 1/2 = 84.3 mrad·cm 1/2 , Δϕ⋅l 1/2 = 58.8 mrad·cm 1/2 ), and the broadest wavelength acceptance bandwidth (8.7 nm). This discovery will contribute to the design of new NCPM materials, at the same time the parameter formula will be helpful for the theoretical prediction of NCPM performance.

  4. Structural Transitions in Cholesteric Liquid Crystal Droplets

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ye; Bukusoglu, Emre; Martínez-González, José A.; Rahimi, Mohammad; Roberts, Tyler F.; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L.; de Pablo, Juan J.

    2016-07-26

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.

  5. Crystal structure of strontium dinickel iron orthophosphate

    Directory of Open Access Journals (Sweden)

    Said Ouaatta

    2015-10-01

    Full Text Available The title compound, SrNi2Fe(PO43, synthesized by solid-state reaction, crystallizes in an ordered variant of the α-CrPO4 structure. In the asymmetric unit, two O atoms are in general positions, whereas all others atoms are in special positions of the space group Imma: the Sr cation and one P atom occupy the Wyckoff position 4e (mm2, Fe is on 4b (2/m, Ni and the other P atom are on 8g (2, one O atom is on 8h (m and the other on 8i (m. The three-dimensional framework of the crystal structure is built up by [PO4] tetrahedra, [FeO6] octahedra and [Ni2O10] dimers of edge-sharing octahedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge-sharing octahedra ([Ni2O10] dimer linked to [PO4] tetrahedra via common edges while the second layer is built up from a strontium row followed by infinite chains of alternating [PO4] tetrahedra and FeO6 octahedra sharing apices. The layers are held together through vertices of [PO4] tetrahedra and [FeO6] octahedra, leading to the appearance of two types of tunnels parallel to the a- and b-axis directions in which the Sr cations are located. Each Sr cation is surrounded by eight O atoms.

  6. Structural and electrical properties of Na{sub 1/2}Gd{sub 1/2}TiO{sub 3} nanoceramics

    Energy Technology Data Exchange (ETDEWEB)

    Barik, Subrat K [Department of Physics and Meteorology, IIT Kharagpur, Kharagpur 721302 (India); Choudhary, R N.P. , [Department of Physics and Meteorology, IIT Kharagpur, Kharagpur 721302 (India); Mahapatra, P K [Department of Physics and Technophysics, Vidyasagar University, Midnapur 721102, West Bengal (India)

    2008-07-14

    The polycrystalline fine (i.e., 38 nm) powder of Na{sub 1/2}Gd{sub 1/2}TiO{sub 3} was prepared by a high-temperature solid-state reaction technique. The formation of single phase compound was confirmed by an X-ray diffraction technique. A preliminary structural analysis exhibited the orthogonal crystal structure of the compound. The surface morphology was studied by scanning electron microscopy. The dielectric permittivity and the loss tangent of the pellet sample were obtained in a wide frequency range (1 kHz-1 MHz) at different temperatures (28-500 deg. C). A dielectric anomaly was observed at 73 deg. C which may be related to ferroelectric-paraelectric phase transition. The ferroelectric transition was confirmed by observation of hysteresis loop at room temperature. Electrical properties of the pellet sample were studied using an AC impedance spectroscopic technique. Detailed analysis of impedance spectra indicated the bulk contribution to electrical properties below 375 deg. C, and the grain boundary above 375 deg. C. The negative temperature coefficient of resistance (NTCR) effect and the temperature dependant electrical relaxation phenomenon in the sample were also observed. Studies of DC conductivity exhibited that the material has a thermally activated process. AC conductivity spectrum obeys Jonscher's universal power law.

  7. Structure and magnetic properties of Gd2Co17-xCr x (1.17 ≤ x ≤ 3.0) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Tegus, O.; Dagula, W.; Brueck, E.; Klaasse, J.C.P.; Buschow, K.H.J.

    2007-01-01

    The structure and magnetic properties of Gd 2 Co 17-x Cr x (1.17 ≤ x ≤ 3.0) compounds have been investigated by means of X-ray diffraction (XRD) and magnetization measurements. The powder X-ray diffraction patterns show that all samples crystallize as a single phase with the rhombohedral Th 2 Zn 17 -type structure. The lattice parameters a and the unit cell volume V increases slightly with increasing Cr content, but the c parameter varies in a less simple way with increasing Cr content. The X-ray diffraction patterns of the magnetically aligned samples show that all compounds investigated have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. The Curie temperature T C , the spin reorientation temperature T sr , the spontaneous magnetization M 0 and the saturation magnetization M s decrease with the increasing Cr content. The anisotropy constant K 1 and the anisotropy field B a of the compounds at room temperature reach a maximum for x = 1.76. The M 0 and M s increase with increasing temperature from 5 K to 300 K. The easy-axis anisotropy of all compounds changes to easy-plane anisotropy at low temperatures and the spin reorientation phenomena are more pronounced for low Cr concentration

  8. Preparation, structural, optical, electrical, and magnetic characterisation of orthorhombic GdCr{sub 0.3}Mn{sub 0.7}O{sub 3} multiferroic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Deepa; Bamzai, K.K. [Jammu Univ. (India). Crystal Growth and Materials Research Laboratory

    2017-04-01

    In this article, chromium-doped gadolinium manganate (GdCr{sub 0.3}Mn{sub 0.7}O{sub 3}) nanoparticles has been prepared by wet-chemical route in order to investigate their structural, optical, electrical, and room temperature magnetic properties. Microstructural and compositional analyses have been carried out by X-ray diffraction and scanning electron microscopy (SEM). Synthesised material is found to be in orthorhombic crystal structure with Pbnm space group. The spherical morphology of the nanoparticles has been examined from the SEM images. Functional groups have been identified using Fourier transform infrared spectroscopy. Dielectric constant, dielectric loss, AC conductivity (σ{sub ac}), and activation energy in the range of 1 kHz-1 MHz from room temperature to high temperature (400 C) have been investigated. The frequency dependence of AC conductivity obeys the universal power law. The value of activation energy depends on increase in frequency. Room temperature magnetic behaviour suggests the material to be paramagnetic in nature.

  9. Structural and optical properties of Gd implanted GaN with various crystallographic orientations

    Czech Academy of Sciences Publication Activity Database

    Macková, Anna; Malinský, Petr; Jagerová, Adéla; Sofer, Z.; Klímová, K.; Sedmidubský, D.; Pristovsek, M.; Mikulics, M.; Lorinčík, Jan; Bottger, R.; Akhmadaliev, S.

    2017-01-01

    Roč. 638, SEP (2017), s. 63-72 ISSN 0040-6090 R&D Projects: GA ČR GA13-20507S; GA ČR GA15-01602S; GA MŠk LM2015056 Institutional support: RVO:67985882 ; RVO:61389005 Keywords : GaN implantation * RBS channelling * optical properties of Gd implanted GaN Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders; BH - Optics, Masers, Lasers (URE-Y) OBOR OECD: 1.3 Physical sciences; Optics (including laser optics and quantum optics) (URE-Y) Impact factor: 1.879, year: 2016

  10. General synthesis and structural evolution of a layered family of Ln8(OH)20Cl4 x nH2O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y).

    Science.gov (United States)

    Geng, Fengxia; Matsushita, Yoshitaka; Ma, Renzhi; Xin, Hao; Tanaka, Masahiko; Izumi, Fujio; Iyi, Nobuo; Sasaki, Takayoshi

    2008-12-03

    The synthesis process and crystal structure evolution for a family of stoichiometric layered rare-earth hydroxides with general formula Ln(8)(OH)(20)Cl(4) x nH(2)O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y; n approximately 6-7) are described. Synthesis was accomplished through homogeneous precipitation of LnCl(3) x xH(2)O with hexamethylenetetramine to yield a single-phase product for Sm-Er and Y. Some minor coexisting phases were observed for Nd(3+) and Tm(3+), indicating a size limit for this layered series. Light lanthanides (Nd, Sm, Eu) crystallized into rectangular platelets, whereas platelets of heavy lanthanides from Gd tended to be of quasi-hexagonal morphology. Rietveld profile analysis revealed that all phases were isostructural in an orthorhombic layered structure featuring a positively charged layer, [Ln(8)(OH)(20)(H(2)O)(n)](4+), and interlayer charge-balancing Cl(-) ions. In-plane lattice parameters a and b decreased nearly linearly with a decrease in the rare-earth cation size. The interlamellar distance, c, was almost constant (approximately 8.70 A) for rare-earth elements Nd(3+), Sm(3+), and Eu(3+), but it suddenly decreased to approximately 8.45 A for Tb(3+), Dy(3+), Ho(3+), and Er(3+), which can be ascribed to two different degrees of hydration. Nd(3+) typically adopted a phase with high hydration, whereas a low-hydration phase was preferred for Tb(3+), Dy(3+), Ho(3+), Er(3+), and Tm(3+). Sm(3+), Eu(3+), and Gd(3+) samples were sensitive to humidity conditions because high- and low-hydration phases were interconvertible at a critical humidity of 10%, 20%, and 50%, respectively, as supported by both X-ray diffraction and gravimetry as a function of the relative humidity. In the phase conversion process, interlayer expansion or contraction of approximately 0.2 A also occurred as a possible consequence of absorption/desorption of H(2)O molecules. The hydration difference was also evidenced by refinement results. The number of coordinated water

  11. Pr:Ca1-xRxF2+x (R=Y or Gd) crystals: Modulated blue, orange and red emission spectra with the proportion of R3+ ions

    Science.gov (United States)

    Yu, Hao; Qian, Xiaobo; Guo, Linyang; Jiang, Dapeng; Wu, Qinghui; Tang, Fei; Su, Liangbi; Ju, Qiangwen; Wang, Jingya; Xu, Jun

    2018-04-01

    The spectroscopic properties of 0.6at.%:Pr:Ca1-xRxF2+x (R = Y, Gd; x = 0,0.006, 0.012, 0.03, 0.06) crystals were investigated and compared. The XRD tests were conducted and the cell dimensions of the crystals were calculated. Room temperature absorption spectra have been registered and analyzed. The emission spectra and decay curves of the crystals were obtained at room temperature. Increasing the proportion of the lattice regulators of Y3+ or Gd3+ ions could significantly enhance the luminescence intensity of all visible emission bands with different ratios. Particularly, the emission intensity ratio of orange to red increased from 0.15 to 1.9 in Pr:Ca1-xYxF2+x crystals and to 1.02 in Pr:Ca1-xGdxF2+x crystals, respectively. Furthermore, Pr:Ca1-xGdxF2+x crystals have substantially strong emission at orange and red region of 580-660 nm, comparable with blue light at 482 nm. The quantum efficiency of the crystals increased rapidly with the increment of R3+ concentration, and finally tend to be 100%.

  12. Crystal structure of a snake venom cardiotoxin

    International Nuclear Information System (INIS)

    Rees, B.; Samama, J.P.; Thierry, J.C.; Gilibert, M.; Fischer, J.; Schweitz, H.; Lazdunski, M.; Moras, D.

    1987-01-01

    Cardiotoxin V/sup II/4 from Naja mossambica crystallizes in space group P6 1 (a = b = 73.9 A; c = 59.0 A) with two molecules of toxin (molecular mass = 6715 Da) in the asymmetric unit. The structure was solved by using a combination of multiple isomorphous replacement and density modification methods. Model building and least-squares refinement led to an agreement factor of 27% for a data set to 3-A resolution prior to any inclusion of solvent molecules. The topology of the molecule is similar to that found in short and long snake neurotoxins, which block the nicotinic acetylcholine receptor. Major differences occur in the conformation of the central loop, resulting in a change in the concavity of the molecule. Hydrophobic residues are clustered in two distinct areas. The existence of stable dimeric entities in the crystalline state, with the formation of a six-stranded antiparallel β sheet, may be functionally relevant

  13. Electronic structure of single crystal C60

    International Nuclear Information System (INIS)

    Wu, J.; Shen, Z.X.; Dessau, D.S.; Cao, R.; Marshall, D.S.; Pianetta, P.; Lindau, I.; Yang, X.; Terry, J.; King, D.M.; Wells, B.O.; Elloway, D.; Wendt, H.R.; Brown, C.A.; Hunziker, H.; Vries, M.S. de

    1992-01-01

    We report angle-resolved photoemission data from single crystals of C 60 cleaved in UHV. Unlike the other forms of pure carbon, the valence band spectrum of C 60 consists of many sharp features that can be essentially accounted for by the quantum chemical calculations describing individual molecules. This suggests that the electronic structure of solid C 60 is mainly determined by the bonding interactions within the individual molecules. We also observe remarkable intensity modulations of the photoemission features as a function of photon energy, suggesting strong final state effects. Finally, we address the issue of the band width of the HOMO state of C 60 . We assert that the width of the photoemission peak of C 60 does not reflect the intrinsic band width because it is broadened by the non 0-0 transitions via the Franck-Condon principle. Our view point provides a possible reconciliation between these photoemission data and those measured by other techniques. (orig.)

  14. Crystal growth and optical properties of Gd admixed Ce-doped Lu.sub.2./sub.Si.sub.2./sub.O.sub.7./sub. single crystals

    Czech Academy of Sciences Publication Activity Database

    Horiai, T.; Kurosawa, S.; Murakami, R.; Yamaji, A.; Shoji, Y.; Ohashi, Y.; Pejchal, Jan; Kamada, K.; Yokota, Y.; Yoshikawa, A.

    2017-01-01

    Roč. 468, Jun (2017), s. 391-394 ISSN 0022-0248 Grant - others:AV ČR(CZ) JSPS-17-18 Program:Bilaterální spolupráce Institutional support: RVO:68378271 Keywords : growth from melt * seed crystals * single crystal growth * oxides * scintillator materials Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.751, year: 2016

  15. Judd–Ofelt analysis and transition probabilities of Er{sup 3+} doped KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Martínez de Mendívil, Jon, E-mail: jon.martinez@uam.es [Departamento de Física de Materiales, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Lifante, Ginés [Departamento de Física de Materiales, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Pujol, Maria Cinta; Aguiló, Magdalena; Díaz, Francesc [Física i Cristalografia de Materials i Nanomaterials (FiCMA-FiCNA), Universitat Rovira i Virgili, Tarragona (Spain); Cantelar, Eugenio [Departamento de Física de Materiales, Universidad Autónoma de Madrid, 28049 Madrid (Spain)

    2015-09-15

    In this work the transition probabilities, radiative lifetimes and branching ratios of Er{sup 3+} ions in KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals have been determined. With this aim, Er{sup 3+} doped KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals have been grown by means of the high temperature Top-Seeded Solution Growth. A spectroscopic analysis of Er{sup 3+} ions in this crystal has been performed following anisotropic Judd–Ofelt analysis to obtain basic spectroscopic properties. A quantum efficiency over 97% has been determined for the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition, indicating that this material is adequate for the development of lasers and amplifiers working in the third telecommunication window. - Highlights: • Er{sub 0.01}:KY{sub 1−x−y}Gd{sub x}Lu{sub y}(WO{sub 4}){sub 2} crystals have been grown. • Anisotropic Judd Ofelt analysis has been carried out. • Optical transition probabilities and branching ratios have been calculated. • Radiative and non-radiative lifetimes have been obtained.

  16. Enhanced refrigerant capacity in Gd-Al-Co microwires with a biphase nanocrystalline/amorphous structure

    Energy Technology Data Exchange (ETDEWEB)

    Shen, H. X. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Department of Physics, University of South Florida, Tampa, Florida 33620 (United States); Xing, D. W.; Liu, Y. F.; Sun, J. F. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Sánchez Llamazares, J. L. [Instituto Potosino de Investigación Científica y Tecnológica A.C., Camino a la Presa San José 2055 Col. Lomas 4a, San Luis Potosí, S.L.P. 78216 (Mexico); Sánchez-Valdés, C. F. [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, AP 14, Ensenada 22860, Baja California (Mexico); Belliveau, H.; Srikanth, H.; Phan, M. H., E-mail: phanm@usf.edu [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States); Wang, H.; Qin, F. X. [Institute for Composites Science and Innovation (InCSI), College of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2016-02-29

    A class of biphase nanocrystalline/amorphous Gd{sub (50+5x)}Al{sub (30−5x)}Co{sub 20} (x = 0, 1, 2) microwires fabricated directly by melt-extraction is reported. High resolution transmission electron microscopy and Fourier function transform based analysis indicate the presence of a volume fraction (∼20%) of ∼10 nm sized nanocrystallities uniformly embedded in an amorphous matrix. The microwires possess excellent magnetocaloric properties, with large values of the isothermal entropy change (−ΔS{sub M} ∼ 9.7 J kg{sup −1} K{sup −1}), the adiabatic temperature change (ΔT{sub ad} ∼ 5.2 K), and the refrigerant capacity (RC ∼ 654 J kg{sup −1}) for a field change of 5 T. The addition of Gd significantly alters T{sub C} while preserving large values of the ΔS{sub M} and RC. The nanocrystallites allow for enhanced RC as well as a broader operating temperature span of a magnetic bed for energy-efficient magnetic refrigeration.

  17. Bulk glass ceramics containing Yb{sup 3+}/Er{sup 3+}: β-NaGdF{sub 4} nanocrystals: Phase-separation-controlled crystallization, optical spectroscopy and upconverted temperature sensing behavior

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Daqin, E-mail: dqchen@fjirsm.ac.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Wan, Zhongyi; Zhou, Yan [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Huang, Ping, E-mail: phuang@fjirsm.ac.cn [Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China); Zhong, Jiasong; Ding, Mingye [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Xiang, Weidong; Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Ji, Zhenguo, E-mail: jizg@hdu.edu.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China)

    2015-07-25

    Highlights: • Hexagonal NaGdF{sub 4} nanocrystals embedded bulk glass ceramics were fabricated. • The incorporation of Ln{sup 3+} dopants into the β-NaGdF{sub 4} lattice was demonstrated. • Upconversion luminescence was highly intensified after glass crystallization. • Such glass ceramics had possible application in the optical temperature sensors. - Abstract: Lanthanide doped hexagonal β-NaGdF{sub 4} nanocrystals embedded transparent bulk glass ceramics were successfully fabricated via a phase-separation-controlled crystallization route. Elemental mapping in the scanning transmission electron microscope and optical spectroscopy analysis demonstrated the partition of the active centers into the β-NaGdF{sub 4} crystalline lattice. As a result, upconversion luminescence of the glass ceramic co-doped with Yb{sup 3+} and Er{sup 3+} is about 60 times as high as that of the precursor glass, attributing to the modification of Yb{sup 3+}/Er{sup 3+} surrounding from phase-separated amorphous nanoparticle to β-NaGdF{sub 4} crystalline lattice with low phonon energy and high crystallinity after crystallization. Furthermore, the temperature-dependent green upconversion emissions assigned to {sup 2}H{sub 11/2} → {sup 4}I{sub 15/2} (520 nm) and {sup 4}S{sub 3/2} → {sup 4}I{sub 15/2} (540 nm) transitions were investigated, and the corresponding fluorescence intensity ratio of these two thermally coupled emitting-states greatly enhanced with increase of temperature. Using such fabricated glass ceramic as an optical thermometric medium, the maximum sensitivity reached as high as 0.0037 K{sup −1} at 580 K. It is expected that the investigated Er{sup 3+}/Yb{sup 3+} codoped glass ceramic might be a very promising candidate for accurate optical temperature sensors.

  18. Optical and scintillation properties of Sr7%:Ce15%:GdF.sub.3./sub. single crystal

    Czech Academy of Sciences Publication Activity Database

    Fukabori, A.; Kamada, K.; Yanagida, T.; Chani, V.; Aoki, K.; Yokota, Y.; Maeo, S.; Nikl, Martin; Yoshikawa, A.

    2011-01-01

    Roč. 318, č. 1 (2011), s. 1175-1178 ISSN 0022-0248. [International Conference on Crystal Growth (ICCG16) /16./ and International Conference on Vapor Growth and Epitaxy (ICVGE14) /14./. Beijing, 08.08.2010-13.08.2010] Institutional research plan: CEZ:AV0Z10100521 Keywords : radiation * inorganic compounds * scintillator materials * scintillators Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.726, year: 2011

  19. Crystal-field analysis for RE3+ ions in laser materials: II. Absorption spectra and energy levels calculations for Nd3+ ions doped into SrLaGa3O7 and BaLaGa3O7 crystals and Tm3+ ions in SrGdGa3O7

    International Nuclear Information System (INIS)

    Karbowiak, M.; Gnutek, P.; Rudowicz, C.; Ryba-Romanowski, W.

    2011-01-01

    Graphical abstract: In this paper we report a detailed analysis of spectroscopic data obtained from low temperature absorption spectra, which enabled assignment of energy levels, and subsequently their analysis in terms of the free-ion and crystal field (CF) parameters. Highlights: → Polarized absorption spectra measured for Nd 3+ and Tm 3+ ions in ABC 3 O 7 crystals. → Energy levels analyzed in terms of the free-ion and crystal-field (CF) parameters. → The combined ADS/SPM procedure have been successfully applied. → The B-bar k parameters and the power law exponents t k of SPM model are determined. → The energies of levels are important for evaluation of the emission cross-section. - Abstract: Low temperature polarized absorption spectra are analyzed to achieve assignments of energy levels for Nd 3+ and Tm 3+ ions at monoclinic C s site symmetry in ABC 3 O 7 crystals. Based on the concept of average optical center, the experimental energy levels for single crystals of SrLaGa 3 O 7 :Nd 3+ (SLG:Nd), BaLaGa 3 O 7 :Nd 3+ (BLG:Nd), and SrGdGa 3 O 7 :Tm 3+ (SGG:Tm) were analyzed in terms of the free-ion parameters and the crystal field (CF) ones, B kq . Assignments of the energy levels resolved in the spectra were done in stages applying the ascent/descent in symmetry method in CF analysis. The actual monoclinic C s site symmetry at the metal centers in ABC 3 O 7 crystals and the approximated orthorhombic C 2v and tetragonal C 4v symmetry were considered. The starting values of B kq 's for SLG:Nd and BLG:Nd crystals were obtained from superposition model (SPM) analysis. The final fitted crystal field parameters show high compatibility with the existing data for structurally similar ion-host systems. The obtained values of the intrinsic parameters provide basis for SPM analysis of CF parameters for rare earth ions in other similar systems, especially those exhibiting low-symmetry sites. The SPM parameters derived for SLG:Nd are used for simulation and

  20. Formamidinium iodide: crystal structure and phase transitions

    Directory of Open Access Journals (Sweden)

    Andrey A. Petrov

    2017-04-01

    Full Text Available At a temperature of 100 K, CH5N2+·I− (I, crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002 Å, and the C—N bond lengths are 1.301 (7 and 1.309 (8 Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643 (10 Å. The cation and anion of I form a tight ionic pair by a strong N—H...I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N—H...I hydrogen bonds. The hydrogen-bonded chains are further packed in stacks along [100]. The thermal behaviour of I was studied by different physicochemical methods (thermogravimetry, differential scanning calorimetry and powder diffraction. Differential scanning calorimetry revealed three narrow endothermic peaks at 346, 387 and 525 K, and one broad endothermic peak at ∼605 K. The first and second peaks are related to solid–solid phase transitions, while the third and fourth peaks are attributed to the melting and decomposition of I. The enthalpies of the phase transitions at 346 and 387 K are estimated as 2.60 and 2.75 kJ mol−1, respectively. The X-ray powder diffraction data collected at different temperatures indicate the existence of I as the monoclinic (100–346 K, orthorhombic (346–387 K and cubic (387–525 K polymorphic modifications.

  1. A comprehensive investigation of tetragonal Gd-doped BiVO{sub 4} with enhanced photocatalytic performance under sun-light

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yangyang; Tan, Guoqiang, E-mail: tan3114@163.com; Dong, Guohua; Ren, Huijun; Xia, Ao

    2016-02-28

    Graphical abstract: - Highlights: • Tetragonal Gd-BiVO{sub 4} with enhanced photocatalytic activity was synthesized. • Gd doping can induce the phase transition from monoclinic to tetragonal BiVO{sub 4}. • GdVO{sub 4} seeds as crystal nucleus dominate the formation of tetragonal Gd-BiVO{sub 4}. • Tetragonal Gd-BiVO{sub 4} exhibits the excellent separation of electrons and holes. • The contribution of high photocatalytic activity under sun-light is from UV-light. - Abstract: Tetragonal Gd-doped BiVO{sub 4} having enhanced photocatalytic activity have been synthesized by a facile microwave hydrothermal method. The structural analysis indicates that Gd doping can induce the phase transition from monoclinic to tetragonal BiVO{sub 4}. The reaction results in precursor solutions imply that tetragonal GdVO{sub 4} seeds as crystal nucleus are the original and determined incentives to force the formation of tetragonal Gd-BiVO{sub 4}. The influences of the surface defect, band structure, and BET surface area on the improved photocatalytic activities of tetragonal Gd-doped BiVO{sub 4} are investigated systematically. The results demonstrate that the more surface oxygen deficiencies as active sites and the excellent mobility and separation of photogenerated electrons and holes are beneficial to the enhancement of the photocatalytic performance of tetragonal Gd-BiVO{sub 4}. The RhB photodegradation experiments indicate that the contribution of high photocatalytic activities under simulated sun-light is mainly from UV-light region due to the tetragonal structure feature. The best photocatalytic performance is obtained for tetragonal 10 at% Gd-BiVO{sub 4}, of which the RhB degradation rate can reach to 96% after 120 min simulated sun-light irradiation. The stable tetragonal Gd-BiVO{sub 4} with efficient mineralization will be a promising photocatalytic material applied in water purification.

  2. Hydrothermal synthesis of Gd2O3:Eu3+ nanophosphors: Effect of surfactant on structural and luminescence properties

    International Nuclear Information System (INIS)

    Dhananjaya, N.; Nagabhushana, H.; Sharma, S.C.; Rudraswamy, B.; Shivakumara, C.; Nagabhushana, B.M.

    2014-01-01

    Highlights: • Gd(OH) 3 :Eu 3+ , GdOOH:Eu 3+ and Gd 2 O 3 :Eu 3+ phases were prepared by hydrothermal method. • Phosphors were well characterized by XRD, SEM, TEM, Raman, UV–Vis, FT-IR. • Cubic Gd 2 O 3 :Eu 3+ show intense red emission, which was highly useful for photonics application. • HDA surfactant plays an important role in conversion of cubic to hexagonal phases. -- Abstract: Various morphologies of Eu 3+ activated gadolinium oxide have been prepared by hydrothermal method using hexadecylamine (HDA) as surfactant at different experimental conditions. The powder X-ray diffraction studies reveal as-formed product is hexagonal Gd(OH) 3 :Eu 3+ phase and subsequent heat treatment at 350 and 600 °C transforms to monoclinic GdOOH:Eu 3+ and cubic Gd 2 O 3 :Eu 3+ phases respectively. SEM pictures of without surfactant show irregular shaped rods along with flakes. However, in the presence of HDA surfactant, the particles are converted into rods of various sizes. The temperature dependent morphological evolution of Gd 2 O 3 :Eu 3+ without and with HDA surfactant is studied. TEM micrographs of Gd(OH) 3 :Eu 3+ sample with HDA confirms smooth nanorods with various diameters in the range 20–100 nm. FTIR studies reveal that HDA surfactant plays an important role in conversion of cubic to hexagonal phases. Among these three phases, cubic phase Gd 2 O 3 :Eu 3+ (λ ex = 254 nm) show red emission at 612 nm corresponding to 5 D 0 → 7 F 2 and is more efficient host than the monoclinic counterpart. The band gap for hexagonal Gd(OH) 3 :Eu 3+ is more when compared to monoclinic GdOOH:Eu 3+ and cubic Gd 2 O 3 :Eu 3+

  3. Pr and Gd co-doped bismuth ferrite thin films with enhanced ...

    Indian Academy of Sciences (India)

    in Pr content, the crystal structures of BPGFO thin films retain rhombohedral (R3c) symmetry accompanied by structure distortion. ... Pr and Gd co-modified BiFeO3 thin film; ferroelectric properties; sol-gel. 1. Introduction. In recent years, great attention has been paid to single- phase BiFeO3 (BFO) multiferroic materials ...

  4. Dual-wavelength mid-infrared CW and Q-switched laser in diode end-pumped Tm,Ho:GdYTaO4 crystal

    Science.gov (United States)

    Wang, Beibei; Gao, Congcong; Dou, Renqin; Nie, Hongkun; Sun, Guihua; Liu, Wenpeng; Yu, Haijuan; Wang, Guoju; Zhang, Qingli; Lin, Xuechun; He, Jingliang; Wang, Wenjun; Zhang, Bingyuan

    2018-02-01

    Dual-wavelength continuous-wave and Q-switched lasers are demonstrated in a Tm,Ho:GdYTaO4 crystal under 790 nm laser diode end pumping for the first time to the best of our knowledge. The laser operates with a dual wavelength at 1949.677 nm and 2070 nm for continuous-wave with a spacing of about 120 nm. The maximum output power is 0.332 W with a pump power of 3 W. By using graphene as the saturable absorber, a passively Q-switched operation is performed with a dual-wavelength at 1950.323 nm and 2068.064 nm with a wavelength interval of about 118 nm. The maximum average output power of the Q-switched laser goes up to 200 mW with a minimum pulse duration of 1.2 µs and a maximum repetition rate of 34.72 kHz.

  5. Spin-phonon and lattice contributions to the ground-state splitting of Gd3+ and Eu2+ in scheelite crystals

    Science.gov (United States)

    Gorlov, A. D.

    2015-07-01

    The EPR spectra of Gd3+ in CaWO4 single crystals have been studied at temperatures T = 1.8, 4.2, and 114-300 K, and the temperature dependence of the parameters b {/n m } ( T) of the spin Hamiltonian has been found. The behavior of b {2/0}( T) has been analyzed. The spin-phonon and static lattice contributions b {2/0}( F) and b {2/0}( L) to b {2/0}( T) have been revealed. For this purpose, the variation of b {2/0}( L) has been calculated taking into account the thermal shifts of oxygen ions in CaWO4. Similar analysis has been carried out for CaWO4: Eu2+ based on the EPR data of other authors (Bronstein, Voterra and Harvey, Kiefte). It has been shown that at b {2/0}( F) > 0, the variation of b {2/0}( F) as a function of T for these impurity centers is described well by the Pfister model and a sign change of b {2/0}( T) for Eu2+ is determined by thermal expansion of the lattice.

  6. Lanthanide-activated Na{sub 5}Gd{sub 9}F{sub 32} nanocrystals precipitated from a borosilicate glass: Phase-separation-controlled crystallization and optical property

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Daqin, E-mail: dqchen@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, CAS, Fuzhou 350002 (China); Wan, Zhongyi; Zhou, Yang [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Chen, Yan, E-mail: chenyan@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Yu, Hua; Lu, Hongwei; Ji, Zhenguo [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Huang, Ping, E-mail: phuang@fjirsm.ac.cn [Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, CAS, Fuzhou 350002 (China)

    2015-03-15

    Highlights: • Na{sub 5}Gd{sub 9}F{sub 32} nanocrystals embedded glass ceramics were fabricated for the first time. • Such glass ceramics were achieved by phase-separation-controlled crystallization. • Elemental mapping evidenced the segregation of activators into the Na{sub 5}Gd{sub 9}F{sub 32} lattice. • Luminescent color could be tuned by controlling glass crystallization temperature. - Abstract: Lanthanide-activated cubic Na{sub 5}Gd{sub 9}F{sub 32} nanocrystals were precipitated from a borosilicate glass with a specifically designed composition. The precursor glass is already phase-separated after melt-quenching, which is beneficial to the realization of the controllable glass crystallization for affording desirable size, morphology and activator partition. Elemental mapping in the scanning transmission electron microscopy evidenced that the segregation of lanthanide ions into the Na{sub 5}Gd{sub 9}F{sub 32} lattice was in situ formed without the requirement of long-range ionic diffusion. Impressively, such fabricated glass ceramic co-doped with Yb{sup 3+}/Er{sup 3+} ions exhibited intense upconversion luminescence, which was about 500 times higher than that of the precursor glass, and its luminescent color could be easily tuned from red to green by controlling glass crystallization temperature. It is anticipated that such phase-separation synthesis strategy with precise control over nanostructure of glass ceramics offer a great opportunity to design other highly transparent nanocomposites with a wide range of tunable optical properties.

  7. Passivation of the surfaces of single crystal gadolinium molybdate (Gd/sub 2/(MoO/sub 4/)/sub 3/) against attack by hydrofluoric acid by inert ion beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Bhalla, A; Cross, L E; Tongson, L [Pennsylvania State Univ., University Park (USA). Materials Research Lab.

    1978-01-01

    The passivation effect from inert ion beam bombardment has been studied on a ferroelectric surface. The mechanism in these materials may have some additional contributions because of the polarization charges of the domains and the dipole effect (ion beam and surface species) on the surfaces. For these studies Gd/sub 2/(MoO/sub 4/)/sub 3/ (GMO) crystals were selected. Two possible mechanisms of passivation of GMO surfaces when bombarded with ion beams are discussed.

  8. Effect of Gd{sup 3+} substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Seema [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida 201307 (India); Kumar, Manoj, E-mail: mkumar.phy@gmail.com [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida 201307 (India); Chhoker, Sandeep [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida 201307 (India); Kumar, Arun; Singh, Mahavir [Department of Physics, Himachal Pradesh University, Shimla 5 (India)

    2017-03-15

    Nanoparticles of CoGd{sub x}Fe{sub 2−x}O{sub 4} with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd{sup 3+} substitution effect on different properties of nanocrystalline CoFe{sub 2}O{sub 4} has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd{sup 3+} ions occupy the octahedral site in CoFe{sub 2}O{sub 4}. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd{sup 3+} substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd{sup 3+} substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd{sup 3+} substitution for Fe{sup 3+} at the octahedral sites. Low dielectric loss suggested the applicability of Gd{sup 3+} doped CoFe{sub 2}O{sub 4} nanoparticles for high frequency microwave device applications. - Highlights: • Gd{sup 3+} ions were successfully added in to the spinel lattice of CoFe{sub 2}O{sub 4}. • Magnetic hysteresis loss is influenced by Gd{sup 3+} doping. • All doped samples exhibit normal dielectric dispersion behaviour of spinel ferrites. • UV–vis diffuse spectroscopy concludes band gap is reduced by Gd{sup 3+} doping.

  9. CCDC 1408042: Experimental Crystal Structure Determination : 6,13-dimesitylpentacene

    KAUST Repository

    Shi, Xueliang

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  10. CCDC 1416891: Experimental Crystal Structure Determination : Methyl-triphenyl-germanium

    KAUST Repository

    Bernatowicz, Piotr

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  11. Crystal structure of Clostridium difficile toxin A

    Energy Technology Data Exchange (ETDEWEB)

    Chumbler, Nicole M.; Rutherford, Stacey A.; Zhang, Zhifen; Farrow, Melissa A.; Lisher, John P.; Farquhar, Erik; Giedroc, David P.; Spiller, Benjamin W.; Melnyk, Roman A.; Lacy, D. Borden

    2016-01-11

    Clostridium difficile infection is the leading cause of hospital-acquired diarrhoea and pseudomembranous colitis. Disease is mediated by the actions of two toxins, TcdA and TcdB, which cause the diarrhoea, as well as inflammation and necrosis within the colon. The toxins are large (308 and 270 kDa, respectively), homologous (47% amino acid identity) glucosyltransferases that target small GTPases within the host. The multidomain toxins enter cells by receptor-mediated endocytosis and, upon exposure to the low pH of the endosome, insert into and deliver two enzymatic domains across the membrane. Eukaryotic inositol-hexakisphosphate (InsP6) binds an autoprocessing domain to activate a proteolysis event that releases the N-terminal glucosyltransferase domain into the cytosol. Here, we report the crystal structure of a 1,832-amino-acid fragment of TcdA (TcdA1832), which reveals a requirement for zinc in the mechanism of toxin autoprocessing and an extended delivery domain that serves as a scaffold for the hydrophobic α-helices involved in pH-dependent pore formation. A surface loop of the delivery domain whose sequence is strictly conserved among all large clostridial toxins is shown to be functionally important, and is highlighted for future efforts in the development of vaccines and novel therapeutics.

  12. Autoclave growth, magnetic, and optical properties of GdB6 nanowires

    Science.gov (United States)

    Han, Wei; Wang, Zhen; Li, Qidong; Liu, Huatao; Fan, Qinghua; Dong, Youzhong; Kuang, Quan; Zhao, Yanming

    2017-12-01

    High-quality single crystalline gadolinium hexaboride (GdB6) nanowires have been successfully prepared at very low temperatures of 200-240 °C by a high pressure solid state (HPSS) method in an autoclave with a new chemical reaction route, where Gd, H3BO3, Mg and I2 were used as raw materials. The crystal structure, morphology, valence, magnetic and optical absorption properties were investigated using XRD, FESEM, HRTEM, XPS, SQUID magnetometry and optical measurements. HRTEM images and SAED patterns reveal that the GdB6 nanowires are single crystalline with a preferred growth direction along [001]. The XPS spectrum suggests that the valence of Gd ion in GdB6 is trivalent. The effective magnetic momentum per Gd3+ in GdB6 is about 6.26 μB. The optical properties exhibit weak absorption in the visible light range, but relatively strong absorbance in the NIR and UV range. Low work function and high NIR absorption can make GdB6 nanowires a potential solar radiation shielding material for solar cells or other NIR blocking applications.

  13. Application of a dynamic-nanoindentation method to analyze the local structure of an Fe-18 at.% Gd cast alloy

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yong; Baik, Youl [Dept. of Materials Science and Technology, Dankook University, Cheonan(Korea, Republic of); Moon, Byung M. [Liquid Processing and Casting Technology R and D Group, KITECH, Incheon (Korea, Republic of); Sohn, Dong Seong [Nuclear Engineering Department, UNIST, Ulsan (Korea, Republic of)

    2017-04-15

    A dynamic nanoindentation method was applied to study an Fe-18 at.% Gd alloy as a neutron-absorbing material prepared by vacuum arc-melting and cast in a mold. The Fe-18 at.% Gd cast alloy had a microstructure with matrix phases and an Fe-rich primary dendrite of Fe9Gd. Rietveld refinement of the X-ray spectra showed that the Fe-18 at.% Gd cast alloy consisted of 35.84 at.% Fe3Gd, 6.58 at.% Fe5Gd, 16.22 at.% Fe9Gd, 1.87 at.% Fe2Gd, and 39.49 at.% β-Fe17Gd2. The average nanohardness of the primary dendrite phase and the matrix phases were 8.7 GPa and 9.3 GPa, respectively. The fatigue limit of the matrix phase was approximately 37% higher than that of the primary dendrite phase. The dynamic nanoindentation method is useful for identifying local phases and for analyzing local mechanical properties.

  14. Crystallization and Characterization of Galdieria sulphuraria RUBISCO in Two Crystal Forms: Structural Phase Transition Observed in P21 Crystal Form

    Directory of Open Access Journals (Sweden)

    Boguslaw Stec

    2007-10-01

    Full Text Available We have isolated ribulose-1,5-bisphosphate-carboxylase/oxygenase (RUBISCOfrom the red algae Galdieria Sulphuraria. The protein crystallized in two different crystalforms, the I422 crystal form being obtained from high salt and the P21 crystal form beingobtained from lower concentration of salt and PEG. We report here the crystallization,preliminary stages of structure determination and the detection of the structural phasetransition in the P21 crystal form of G. sulphuraria RUBISCO. This red algae enzymebelongs to the hexadecameric class (L8S8 with an approximate molecular weight 0.6MDa.The phase transition in G. sulphuraria RUBISCO leads from two hexadecamers to a singlehexadecamer per asymmetric unit. The preservation of diffraction power in a phasetransition for such a large macromolecule is rare.

  15. Crystallization of 21.25Gd2O3-63.75MoO3-15B2O3 glass induced by femtosecond laser at the repetition rate of 250 kHz

    International Nuclear Information System (INIS)

    Zhong, M.J.; Han, Y.M.; Liu, L.P.; Zhou, P.; Du, Y.Y.; Guo, Q.T.; Ma, H.L.; Dai, Y.

    2010-01-01

    We report the formation of β'-Gd 2 (MoO 4 ) 3 (GMO) crystal on the surface of the 21.25Gd 2 O 3 -63.75MoO 3 -15B 2 O 3 glass, induced by 250 kHz, 800 nm femtosecond laser irradiation. The morphology of the modified region in the glass was clearly examined by scanning electron microscopy (SEM). By micro-Raman spectra, the laser-induced crystals were confirmed to be GMO phases and it is found that these crystals have a strong dependence on the number and power of the femtosecond laser pulses. When the irradiation laser power was 900 mW, not only the Raman peaks of GMO crystals but also some new peaks at 214 cm -1 , 240 cm -1 , 466 cm -1 , 664 cm -1 and 994 cm -1 which belong to the MoO 3 crystals were observed. The possible mechanisms are proposed to explain these phenomena.

  16. Three phenoxo-bridged dinuclear lanthanide complexes. Syntheses, crystal structures, and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhi-Chao; Dai, Rui-Peng; Yang, En-Cui [College of Chemistry, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Tianjin Normal University (China); Dong, Hui-Ming; Zhao, Xiao-Jun [College of Chemistry, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Tianjin Normal University (China); Department of Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin (China)

    2018-03-15

    Three dinuclear lanthanide complexes [Ln{sub 2}(H{sub 2}L){sub 2}(NO{sub 3}){sub 4}] [Ln = Dy (1), Tb (2), and Gd (3)] [H{sub 3}L = 2-hydroxyimino-N'-[(2-hydroxy-3-methoxyphenyl)methylidene]- propanohydrazone] were solvothermally synthesized by varying differently anisotropic rare earth ions. Single-crystal structural analyses demonstrate that all the three complexes are crystallographically isostructural with two centrosymmetric Ln{sup III} ions aggregated by a pair of monodeprotonated H{sub 2}L{sup -} anions. Weak intramolecular antiferromagnetic interactions with different strength were mediated by a pair of phenoxo bridges due to superexchange and/or single-ion anisotropy. Additionally, the Dy{sup III}-based entity shows the strongest anisotropy exhibits field-induced single-molecule magnetic behavior with two thermally activated relaxation processes. In contrast, 3 with isotropic Gd{sup III} ion has a significant cryogenic magnetocaloric effect with the maximum entropy change of 25.7 J.kg{sup -1}.K{sup -1} at 2.0 K and 70.0 kOe. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Rebuttal of the existence of solid rare earth bicarbonates and the crystal structure of holmium nitrate pentahydrate

    Energy Technology Data Exchange (ETDEWEB)

    Rincke, Christine; Schmidt, Horst; Voigt, Wolfgang [Institute for Inorganic Chemistry, TU Bergakademie Freiberg (Germany)

    2017-03-16

    The synthesis routes of Gd(HCO{sub 3}){sub 3}.5H{sub 2}O and Ho(HCO{sub 3}){sub 3}.6H{sub 2}O, which are the only known bicarbonates of rare earth metals, were refuted and the published crystal structures were discussed. Because of the structural relationship of Ho(HCO{sub 3}){sub 3}.6H{sub 2}O to rare earth nitrate hexahydrates,[] the synthesis of holmium nitrate hydrate was considered and the crystal structure of Ho(NO{sub 3}){sub 3}.5H{sub 2}O was solved by single crystal X-ray diffraction measurements. Ho(NO{sub 3}){sub 3}.5H{sub 2}O was determined to crystallize in the triclinic space group P1 (no. 2) with a = 6.5680(14) Aa, b = 9.503(2) Aa, c = 10.462(2) Aa, α = 63.739(14) , β = 94.042(2) and γ = 76.000(16) . The crystal structure consists of isolated [Ho(H{sub 2}O){sub 4}(NO{sub 3}){sub 3}] polyhedra and non-coordinating water molecules. It is isotypic to other rare earth nitrate pentahydrates. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Band structures in fractal grading porous phononic crystals

    Science.gov (United States)

    Wang, Kai; Liu, Ying; Liang, Tianshu; Wang, Bin

    2018-05-01

    In this paper, a new grading porous structure is introduced based on a Sierpinski triangle routine, and wave propagation in this fractal grading porous phononic crystal is investigated. The influences of fractal hierarchy and porosity on the band structures in fractal graidng porous phononic crystals are clarified. Vibration modes of unit cell at absolute band gap edges are given to manifest formation mechanism of absolute band gaps. The results show that absolute band gaps are easy to form in fractal structures comparatively to the normal ones with the same porosity. Structures with higher fractal hierarchies benefit multiple wider absolute band gaps. This work provides useful guidance in design of fractal porous phononic crystals.

  19. Structural Color Patterns by Electrohydrodynamic Jet Printed Photonic Crystals.

    Science.gov (United States)

    Ding, Haibo; Zhu, Cun; Tian, Lei; Liu, Cihui; Fu, Guangbin; Shang, Luoran; Gu, Zhongze

    2017-04-05

    In this work, we demonstrate the fabrication of photonic crystal patterns with controllable morphologies and structural colors utilizing electrohydrodynamic jet (E-jet) printing with colloidal crystal inks. The final shape of photonic crystal units is controlled by the applied voltage signal and wettability of the substrate. Optical properties of the structural color patterns are tuned by the self-assembly of the silica nanoparticle building blocks. Using this direct printing technique, it is feasible to print customized functional patterns composed of photonic crystal dots or photonic crystal lines according to relevant printing mode and predesigned tracks. This is the first report for E-jet printing with colloidal crystal inks. Our results exhibit promising applications in displays, biosensors, and other functional devices.

  20. Physicochemical and crystal structure analyses of the antidiabetic agent troglitazone.

    Science.gov (United States)

    Kobayashi, Katsuhiro; Fukuhara, Hiroshi; Hata, Tadashi; Sekine, Akiko; Uekusa, Hidehiro; Ohashi, Yuji

    2003-07-01

    The antidiabetic agent troglitazone has two asymmetric carbons located at the chroman ring and the thiazolidine ring and is produced as a mixture of equal amounts of four optical isomers, 2R-5S, 2S-5R, 2R-5R, and 2S-5S. The crystalline powdered drug substance consists of two diastereomer pairs, 2R-5R/2S-5S and 2R-5S/2S-5R. There are many types of crystals obtained from various crystallization conditions. The X-ray structure analysis and the physicochemical analyses of troglitazone were performed. The solvated crystals of the 2R-5R/2S-5S pair were crystallized from several solutions: methanol, ethanol, acetonitrile, and dichloromethane. The ratio of solvent and troglitazone was 1 : 2 (L1/2-form). The monohydrate crystals were obtained from aqueous acetone solution (L1-form). On the other hand, only an anhydrate crystal of the 2R-5S/2S-5R pair was crystallized from various solutions (H0-form). The dihydrous mixed crystal (MA2-form) was obtained from a mixture of the two diastereomer pairs of 2R-5R/2S-5S and 2R-5S/2S-5R in equal amounts by the slow evaporation of aqueous acetone solution. The crystal structure of the MA2-form is similar to the H0-form. When the MA2 crystal was kept under low humidity, it was converted into the dehydrated form (MA0-form) with retention of the single crystal form. The structure of the MA0-form is isomorphous to the H0-form. The MA2-form was converted into the MA0-form and vice versa with retention of the single crystal under low and high humidity, respectively. The crystallization and storage conditions of the drug substances were successfully analyzed.

  1. Experimental and first principle study of the structure, electronic, optical and luminescence properties of M-type GdNbO4 phosphor

    Science.gov (United States)

    Ding, Shoujun; Zhang, Haotian; Zhang, Qingli; Chen, Yuanzhi; Dou, Renqin; Peng, Fang; Liu, Wenpeng; Sun, Dunlu

    2018-06-01

    In this work, GdNbO4 polycrystalline with monoclinic phase was prepared by traditional high-temperature solid-state reaction. Its structure was determined by X-ray diffraction and its unit cell parameters were obtained with Rietveld refinement method. Its luminescence properties (including absorbance, emission and luminescence lifetime) were investigated with experiment method and the CIE chromaticity coordinate was presented. Furthermore, a systematic theoretical calculation (including band gap, density of states and optical properties) based on the density function theory methods was performed on GdNbO4. Lastly, a comparison between experiment and calculated results was conducted. The calculated and experiment results obtained in this work can provide an essential understanding of GdNbO4 material.

  2. Solution growth of the Gd-Cu-Al systems in the low-gadolinium concentration range

    International Nuclear Information System (INIS)

    Uhlirova, Klara; Sechovsky, Vladimir

    2009-01-01

    Solution growth of Gd-Cu-Al resulted in the formation of single crystals of GdCu 4 Al 8 with tetragonal ThMn 12 -type structure (a = 8.751 Aa, c = 5.148 Aa), Gd 2 Cu 9.4-6.7 Al 7.6-10.3 with hexagonal Th 2 Zn 17 -type structure (a = 8.83 Aa c = 1.28 Aa), and Gd(Cu, Al) 4 with orthorhombic CeNi 2+x Sb 2-x -type structure. An antiferromagnetic ordering of GdCu 4 Al 8 was found below 35 K, which is in agreement with the previously reported T N = 35 K and T N = 32 K measured on polycrystalline samples. In the temperature range 50-320 K the magnetic susceptibility χ follows the Curie-Weiss law with μ eff = 7.8 μ B /f.u. and θ p = -17 K for B parallel c, μ eff = 7.9 μ B /f.u. and θ p = - 18 K for B perpendicular to c. The a-axis is the easy magnetization direction. The Gd(Cu, Al) 4 and Gd(Cu, Al) 4 compounds order antiferromagnetically below T N = 35 K and T N = 31 K, respectively. (orig.)

  3. Studies on growth, crystal structure and characterization of novel organic nicotinium trifluoroacetate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dhanaraj, P.V. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Rajesh, N.P., E-mail: rajeshnp@hotmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Sundar, J. Kalyana; Natarajan, S. [Department of Physics, Madurai Kamaraj University, Madurai 625 021 (India); Vinitha, G. [Department of Physics, Crescent Engineering College, Chennai 600 048 (India)

    2011-09-15

    Highlights: {yields} Good quality crystals of nicotinium trifluoroacetate in monoclinic system were grown for first time. {yields} Nicotinium trifluoroacetate crystal exhibits third order nonlinear optical properties. {yields} The optical spectrum of nicotinium trifluoroacetate crystal reveals the wide transmission in the entire range with cutoff wavelength at 286 nm. {yields} Nicotinium trifluoroacetate is a low dielectric constant material. - Abstract: An organic material, nicotinium trifluoroacetate (NTF) was synthesized and single crystals in monoclinic system were grown from aqueous solution for the first time. Its solubility and metastable zone width were estimated. The crystal structure of NTF was analyzed to reveal the molecular arrangements and the formation of hydrogen bonds in the crystal. High-resolution X-ray diffraction rocking curve measurements were performed to analyze the structural perfection of the grown crystals. Functional groups in NTF were identified by Fourier transform infrared spectral analysis. Thermal behaviour and stability of NTF were studied by thermogravimetric and differential thermal analysis and differential scanning calorimetry. Mechanical and dielectric properties of NTF crystals were analyzed. Optical studies reveal that NTF crystals are transparent in the wavelength range 286-1100 nm. The third order nonlinear optical parameters of NTF were derived by the Z-scan technique.

  4. Structural elucidation and magnetic behavior evaluation of rare earth (La, Nd, Gd, Tb, Dy) doped BaCoNi-X hexagonal nano-sized ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Majeed, Abdul, E-mail: abdulmajeed2276@gmail.com [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Khan, Muhammad Azhar, E-mail: azhar.khan@iub.edu.pk [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Raheem, Faseeh ur; Hussain, Altaf; Iqbal, F. [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Murtaza, Ghulam [Centre for Advanced Studies in Physics, Government College University, Lahore 54000 (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Shakir, Imran [Deanship of Scientific Research, College of Engineering, King Saud University, PO Box 800, Riyadh 11421 (Saudi Arabia); Warsi, Muhammad Farooq [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan)

    2016-06-15

    Rare-earth (RE=La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) doped Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19 nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400 cm{sup −1.} Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3b{sub VI}). The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Graphical abstract: Nano-sized rare-earth (RE=La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) doped Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route and the crystallite size was found in the range 7–19 nm. The enhancement in the coercivity was observed with the doping of rare-earth cations. The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Highlights: • Micro-emulsion route was used to synthesize Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} ferrites. • The crystallite size was found

  5. Structural elucidation and magnetic behavior evaluation of rare earth (La, Nd, Gd, Tb, Dy) doped BaCoNi-X hexagonal nano-sized ferrites

    International Nuclear Information System (INIS)

    Majeed, Abdul; Khan, Muhammad Azhar; Raheem, Faseeh ur; Hussain, Altaf; Iqbal, F.; Murtaza, Ghulam; Akhtar, Majid Niaz; Shakir, Imran; Warsi, Muhammad Farooq

    2016-01-01

    Rare-earth (RE=La 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ ) doped Ba 2 NiCoRE x Fe 28−x O 46 (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19 nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400 cm −1. Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3b VI ). The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Graphical abstract: Nano-sized rare-earth (RE=La 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ ) doped Ba 2 NiCoRE x Fe 28−x O 46 (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route and the crystallite size was found in the range 7–19 nm. The enhancement in the coercivity was observed with the doping of rare-earth cations. The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Highlights: • Micro-emulsion route was used to synthesize Ba 2 NiCoRE x Fe 28−x O 46 ferrites. • The crystallite size was found in the range 7–19 nm. • The rare-earth incorporation enhanced the coercivity (664–926 Oe).

  6. Luminescence and structural properties of RbGdS.sub.2./sub. compounds doped by rare earth elements

    Czech Academy of Sciences Publication Activity Database

    Jarý, Vítězslav; Havlák, Lubomír; Bárta, J.; Mihóková, Eva; Nikl, Martin

    2013-01-01

    Roč. 35, č. 6 (2013), s. 1226-1229 ISSN 0925-3467 R&D Projects: GA TA ČR TA01011017 Institutional support: RVO:68378271 Keywords : luminescence * X-ray diffraction * crystal structure * optical materials * ternary sulfides * rare earth s doping Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.075, year: 2013

  7. Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

    Science.gov (United States)

    Wang, Hui; Zhang, Ke-Qin

    2013-01-01

    Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

  8. Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

    Directory of Open Access Journals (Sweden)

    Ke-Qin Zhang

    2013-03-01

    Full Text Available Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors.

  9. New orthorhombic derivative of CaCu{sub 5}-type structure: RNi{sub 4}Si compounds (R=Y, La, Ce, Sm, Gd–Ho), crystal structure and some magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V., E-mail: morozkin@general.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Knotko, A.V. [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Geological Faculty, Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Yuan, Fang; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600036 (India)

    2013-12-15

    The crystal structure of new YNi{sub 4}Si-type RNi{sub 4}Si (R=Y, La, Ce, Sm, Gd–Ho) compounds has been established using powder X-ray diffraction. The YNi{sub 4}Si structure is a new structure type, which is orthorhombic derivative of CaCu{sub 5}-type structure (space group Cmmm N 65, oC12). GdNi{sub 4}Si and DyNi{sub 4}Si compounds order ferromagnetically at 25 and 19 K, respectively whereas YNi{sub 4}Si shows antiferromagnetic nature. At 15 K, DyNi{sub 4}Si shows second antiferromagnetic-like transition. The magnetic moment of GdNi{sub 4}Si at 5 K in 50 kOe field is ∼7.2 μ{sub B}/f.u. suggesting a completely ordered ferromagnetic state. The magnetocaloric effect of GdNi{sub 4}Si is calculated in terms of isothermal magnetic entropy change and it reaches the maximum value of −12.8 J/kg K for a field change of 50 kOe near T{sub C} ∼25 K. - Graphical abstract: The RNi{sub 4}Si (R=Y, La, Ce, Sm, Gd–Ho) compounds crystallize in new YNi{sub 4}Si-type structure which is orthorhombic derivative of the basic CaCu{sub 5}-type structure. GdNi{sub 4}Si and DyNi{sub 4}Si compounds show the ferromagnetic-like ordering, whereas.YNi{sub 4}Si has the antiferromagnetic nature. The GdNi{sub 4}Si demonstrates the big magnetocaloric effect near temperature of ferromagnetic ordering. The relationship between initial CaCu{sub 5}-type DyNi{sub 5} and YNi{sub 4}Si-type DyNi{sub 4}Si lattices.

  10. Elastic properties of Ti-24Nb-4Zr-8Sn single crystals with bcc crystal structure

    International Nuclear Information System (INIS)

    Zhang, Y.W.; Li, S.J.; Obbard, E.G.; Wang, H.; Wang, S.C.; Hao, Y.L.; Yang, R.

    2011-01-01

    Research highlights: → The single crystals of Ti2448 alloy with the bcc crystal structure were prepared. → The elastic moduli and constants were measured by several resonant methods. → The crystal shows significant elastic asymmetry in tension and compression. → The crystal exhibits weak nonlinear elasticity with large elastic strain ∼2.5%. → The crystal has weak atomic interactions against crystal distortion to low symmetry. - Abstract: Single crystals of Ti2448 alloy (Ti-24Nb-4Zr-8Sn in wt.%) were grown successfully using an optical floating-zone furnace. Several kinds of resonant methods gave consistent Young's moduli of 27.1, 56.3 and 88.1 GPa and shear moduli of 34.8, 11.0 and 14.6 GPa for the , and oriented single crystals, and C 11 , C 12 and C 44 of 57.2, 36.1 and 35.9 GPa respectively. Uniaxial testing revealed asymmetrical elastic behaviors of the crystals: tension caused elastic softening with a large reversible strain of ∼4% and a stress plateau of ∼250 MPa, whereas compression resulted in gradual elastic stiffening with much smaller reversible strain. The crystals exhibited weak nonlinear elasticity with a large elastic strain of ∼2.5% and a high strength, approaching ∼20% and ∼30% of its ideal shear and ideal tensile strength respectively. The crystals showed linear elasticity with a small elastic strain of ∼1%. These elastic deformation characteristics have been interpreted in terms of weakened atomic interactions against crystal distortion to low crystal symmetry under external applied stresses. These results are consistent with the properties of polycrystalline Ti2448, including high strength, low elastic modulus, large recoverable strain and weak strengthening effect due to grain refinement.

  11. Perpendicular exchange coupling effects in ferrimagnetic TbFeCo/GdFeCo hard/soft structures

    Science.gov (United States)

    Wang, Ke; Wang, Yahong; Ling, Fujin; Xu, Zhan

    2018-04-01

    Bilayers consisting of magnetically hard TbFeCo and soft GdFeCo alloy were fabricated. Exchange-spring and sharp switching in a step-by-step fashion were observed in the TbFeCo/GdFeCo hard/soft bilayers with increasing GdFeCo thickness. A perpendicular exchange bias field of several hundred Oersteds is observed from the shift of minor loops pinned by TbFeCo layer. The perpendicular exchange energy is derived to be in the range of 0.18-0.30 erg/cm2. The exchange energy is shown to increase with the thickness of GdFeCo layer in the bilayers, which can be attributed to the enhanced perpendicular anisotropy of GdFeCo layer in our experimental range.

  12. The crystal structure and twinning of neodymium gallium perovskite single crystals

    International Nuclear Information System (INIS)

    Ubizskii, S.B.; Vasylechko, L.O.; Savytskii, D.I.; Matkovskii, A.O.; Syvorotka, I.M.

    1994-01-01

    By means of X-ray structure analysis, the crystal structure of neodymium gallium perovskite (NGP) single crystals (NdGaO 3 ) being used as a substrate for HTSC film epitaxy has been refined and the position of atoms has been determined. The possibility of YBa 2 Cu 3 O 7-x film epitaxy on the plane (110) of NGP crystal as well as its advantages and pitfalls are analysed from structural data. The twinning types in the NGP crystal were established. The twinning structure of NGP substrates is found to be stable up to a temperature of 1173 K, as differentiated from the LaGaO 3 and LaAlO 3 substrates. It is intimated that the twinning in the NGP substrates oriented as (001) can result in creation of 90 degrees twin bonds in a film, and in the case of (110)-oriented plates it is possible to ignore the twinning presence in substrate completely. (author)

  13. Preparation and crystal structure of Ca4Sb2O

    International Nuclear Information System (INIS)

    Eisenmann, B.; Limartha, H.; Schaefer, H.

    1980-01-01

    The formerly described compound Ca 2 Sb is to be corrected to Ca 4 Sb 2 O as shown by X-ray diffractometer data of single crystals and neutron diffraction diagrams of powders. The compound crystallizes in the K 2 NiF 4 structure type. (orig.)

  14. Crystal structure of vanadite: Refinement of anisotropic displacement parameters

    Czech Academy of Sciences Publication Activity Database

    Laufek, F.; Skála, Roman; Haloda, J.; Císařová, I.

    2006-01-01

    Roč. 51, 3-4 (2006), s. 271-275 ISSN 1210-8197 Institutional research plan: CEZ:AV0Z30130516 Keywords : anisotropic displacement parameter * crystal structure * single-crystal X-ray refinement * vanadinite Subject RIV: DB - Geology ; Mineralogy

  15. Nucleation of colloidal crystals on configurable seed structures

    NARCIS (Netherlands)

    Hermes, M; Vermolen, E.C.M.; Leunissen, M.E.; Vossen, D.L.J.; van Oostrum, P.D.J.; Dijkstra, M.; van Blaaderen, A.

    2011-01-01

    Nucleation is an important stage in the growth of crystals. During this stage, the structure and orientation of a crystal are determined. However, short time- and length-scales make nucleation poorly understood. Micrometer-sized colloidal particles form an ideal model system to study nucleation due

  16. Effect of Gd{sup 3+} doping and reaction temperature on structural and optical properties of CdS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Gajanan, E-mail: pandeygajanan@rediffmail.com [Department of Applied Chemistry, Babasaheb Bhimrao Ambedkar University, Lucknow, 226025, (U.P.) (India); Dixit, Supriya; Shrivastava, A.K. [School of Studies in Physics, Jiwaji University, Gwalior, 474011, (M.P.) (India)

    2015-10-15

    Graphical abstract: - Highlights: • Cd{sub 1−x}Gd{sub x}S nanoparticles have been prepared in aqueous medium in presence of CTAB. • From XRD, EDX and ICP-OES study, successful doping of Gd{sup 3+} in CdS has been proved. • Gd{sup 3+} doping reduced size of NCs, while temperature increased size and altered shape. • Gd{sup 3+} doping and reaction temperature influenced the optical properties of NCs. - Abstract: CdS and Gd{sup 3+} ions doped CdS nanoparticles have been prepared at two reaction temperatures 90 and 120 °C in aqueous medium in presence of cationic surfactant cetyltrimethylammonium bromide. X-ray diffraction study revealed predominant formation of zinc blend CdS and Gd:CdS at 90 °C, while at 120 °C, phase pure wurtzite CdS and Gd:CdS were formed. From EDX spectra and ICP-OES analysis, successful doping of Gd{sup 3+} ions in CdS host has been proved. Fourier transform infrared spectroscopy results show the interaction of CTAB through headgroup at the nanoparticles surface. In the transmission electron microscopy images, it has been observed that the reaction temperature and Gd{sup 3+} doping played critical role on size and shape of nanocrystals. In UV–visible absorption as well as photoluminescence emission spectra, size and shape-dependent quantum confinement effect has been observed. On Gd{sup 3+} doping, surface states related emission peak shifted to higher wavelength, while intensity of peaks increased on increasing temperature.

  17. External electric field effects on Schottky barrier at Gd3N@C80/Au interface

    Science.gov (United States)

    Onishi, Koichi; Nakashima, Fumihiro; Jin, Ge; Eto, Daichi; Hattori, Hayami; Miyoshi, Noriko; Kirimoto, Kenta; Sun, Yong

    2017-08-01

    The effects of the external electric field on the height of the Schottky barrier at the Gd3N@C80/Au interface were studied by measuring current-voltage characteristics at various temperatures from 200 K to 450 K. The Gd3N@C80 sample with the conduction/forbidden/valence energy band structure had a face-centered cubic crystal structure with the average grain size of several nanometers. The height of the Gd3N@C80/Au Schottky barrier was confirmed to be 400 meV at a low electric field at room temperature. Moreover, the height decreases with the increasing external electric field through a change of permittivity in the Gd3N@C80 sample due to a polarization of the [Gd3] 9 +-[N3 -+("separators="|C80 ) 6 -] dipoles in the Gd3N@C80 molecule. The field-dependence of the barrier height can be described using a power math function of the electric field strength. The results of the field-dependent barrier height indicate that the reduction in the Schottky barrier is due to an image force effect of the transport charge carrier at the Gd3N@C80/Au interface.

  18. Ternary gallides RE_4Rh_9Ga_5, RE_5Rh_1_2Ga_7 and RE_7Rh_1_8Ga_1_1 (RE=Y, La-Nd, Sm, Gd, Tb). Intergrowth structures with MgCu_2 and CaCu_5 related slabs

    International Nuclear Information System (INIS)

    Seidel, Stefan; Rodewald, Ute C.; Poettgen, Rainer; Janka, Oliver

    2017-01-01

    Fourteen ternary gallides RE_4Rh_9Ga_5, RE_5Rh_1_2Ga_7 and RE_7Rh_1_8Ga_1_1 (RE=Y, La-Nd, Sm, Gd, Tb) were synthesized from the elements by arc-melting, followed by different annealing sequences either in muffle or induction furnaces. The samples were characterized through Guinier powder patterns and the crystal structures of Ce_4Rh_9Ga_5, Ce_5Rh_1_2Ga_7, Ce_7Rh_1_8Ga_1_1, Nd_5Rh_1_0_._4_4_(_4_)Ga_8_._5_6_(_4_), Nd_4Rh_9Ga_5 and Gd_4Rh_9Ga_5 were refined from single crystal X-ray diffractometer data. The new gallides are the n=2, 3 and 5 members of the RE_2_+_n Rh_3_+_3_n Ga_1_+_2_n structure series in the Parthe intergrowth concept. The slabs of these intergrowth structures derive from the cubic Laves phase MgCu_2 (Mg_2Ni_3Si as ternary variant) and CaCu_5 (CeCo_3B_2 as ternary variant). Only the Nd_5Rh_1_0_._4_4_(_4_)Ga_8_._5_6_(_4_) crystal shows Rh/Ga mixing within the Laves type slabs. Magnetic susceptibility measurements reveal Pauli paramagnetism for Y_4Rh_9Ga_5 and Curie-Weiss paramagnetism for Gd_4Rh_9Ga_5 and Tb_4Rh_9Ga_5. Low-temperature data show ferromagnetic ordering at T_C=78.1 (Gd_4Rh_9Ga_5) and 55.8 K (Tb_4Rh_9Ga_5).

  19. Anomalous electrical resistance and magnetoresistance in Gd{sub 2}PdSi{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mallik, R; Sampathkumaran, E V [Tata Institute of Fundamental Research, Mumbai (India)

    1997-12-31

    The results of the investigations of electrical resistance (p) in zero field as well as in the presence of magnetic field (up to 70 kOe) and of heat capacity (C) in a new compound, Gd{sub 2}PdSi{sub 3} having AlB{sub 2} type crystal structure are reported. 1 ref., 2 figs.

  20. Thermal expansion of the magnetorefrigerant Gd5(Si,Ge)4

    NARCIS (Netherlands)

    Brück, E.H.; Nazih, M.; de Visser, A.; Zhang, L.; Tegus, O.

    2003-01-01

    We report thermal expansion measurements carried out on a single-crystal of the giant magnetocaloric effect material Gd5(Si0.43Ge0.57)4. At the magneto-structural phase transition at T0~240 K, large steps in the relative length change ÄL/L along the principle crystallographic axes are observed. The

  1. Crystal structure and crystal growth of the polar ferrimagnet CaBaFe4O7

    Science.gov (United States)

    Perry, R. S.; Kurebayashi, H.; Gibbs, A.; Gutmann, M. J.

    2018-05-01

    Magnetic materials are a cornerstone for developing spintronic devices for the transport of information via magnetic excitations. To date, relatively few materials have been investigated for the purpose of spin transport, mostly due to the paucity of suitable candidates as these materials are often chemically complex and difficult to synthesize. We present the crystal growth and a structure solution on the high-temperature crystal structure of the layered, polar ferrimagnet CaBaFe4O7 , which is a possible new contender for spintronics research. The space group is identified as P 3 by refinement of single crystal and powder neutron diffraction data. At 400 K, the trigonal lattice parameters are a =11.0114 (11 )Å and c =10.330 (3 )Å . The structure is similar to the low-temperature phase with alternating layers of triangular and Kagome-arranged Fe-O tetrahedra. We also present details of the crystal growth by traveling solvent method.

  2. Synthesis, crystal structure and Thermogravimetry of ortho-phthalic ...

    Indian Academy of Sciences (India)

    satisfied by two chelated carboxylates while fifth and sixth co-ordination positions are satisfied by monodentate ... Keywords. o-Phthalic acid; coordination polymer; X-ray crystal structure; Copper(II); EPR; TGA. 1. .... Absorption coefficient.

  3. Crystal structure and pair potentials: A molecular-dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Parrinello, M.; Rahman, A.

    1980-10-06

    With use of a Lagrangian which allows for the variation of the shape and size of the periodically repeating molecular-dynamics cell, it is shown that different pair potentials lead to different crystal structures.

  4. Phase relations, crystal structures and physical properties of nuclear fuels

    International Nuclear Information System (INIS)

    Tagawa, Hiroaki; Fujino, Takeo; Tateno, Jun

    1975-07-01

    Phase relations, crystal structures and physical properties of the compounds for nuclear fuels are presented, including melting point, thermal expansion, diffusion and magnetic and electric properties. Emphasis is on oxides, carbides and nitrides of thorium, uranium and plutonium. (auth.)

  5. Structural and microstructural analysis of the U-Gd-O system using X-Ray diffraction data

    International Nuclear Information System (INIS)

    Darin, Gaspar; Imakuma, Kengo; Martinez, Luis G.; Turrrilas, Xabier M.; Ichikawa, Rodrigo U.; Silva, André S.B.; Durazzo, Michelangelo; Riella, Humberto G.; Urano, Elita

    2017-01-01

    Gadolinium is one of the best neutron absorber materials and its usage can be considered as a burnable poison for Light Water Reactors (LWR) and as a sacrificial material in Sodium Fast Reactor (SFR). Most of the experiments in the literature focus on nuclear fuel with up to 12 wt% Gd 2 O 3 . Recently, the phase diagram and melting point has been investigated for high contents of Gd 2 O 3 in the U-Gd-O system, that means a solid solution of the composition (U 1-x , Gd x )O 2 for 0Gd-O system for high contents of Gd 2 O 3 using X-ray diffraction data. Rietveld analysis was applied to obtain cell parameters, atomic positions and atomic displacement factors and compared with literature available. Also, the quantification of phases was performed for the different contents of Gd 2 O 3 in the system. Finally, mean crystallite sizes were determined and correlated with the weight fraction of the phases. (author)

  6. Structural and microstructural analysis of the U-Gd-O system using X-Ray diffraction data

    Energy Technology Data Exchange (ETDEWEB)

    Darin, Gaspar; Imakuma, Kengo; Martinez, Luis G.; Turrrilas, Xabier M.; Ichikawa, Rodrigo U.; Silva, André S.B.; Durazzo, Michelangelo; Riella, Humberto G.; Urano, Elita, E-mail: gaspardarin@gmail.com, E-mail: kimakuma@ipen.br, E-mail: lgallego@ipen.br, E-mail: ichikawa@usp.br, E-mail: andre.santos.silva@ipen.br, E-mail: mdurazzo@ipen.br, E-mail: riella@enq.ufsc.br, E-mail: elitaucf@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Combustíveis Nuclear; Institute of Material Science of Barcelona (ICMAB) Barcelona (Spain)

    2017-11-01

    Gadolinium is one of the best neutron absorber materials and its usage can be considered as a burnable poison for Light Water Reactors (LWR) and as a sacrificial material in Sodium Fast Reactor (SFR). Most of the experiments in the literature focus on nuclear fuel with up to 12 wt% Gd{sub 2}O{sub 3}. Recently, the phase diagram and melting point has been investigated for high contents of Gd{sub 2}O{sub 3} in the U-Gd-O system, that means a solid solution of the composition (U{sub 1-x}, Gd{sub x})O{sub 2} for 0Gd-O system for high contents of Gd{sub 2}O{sub 3} using X-ray diffraction data. Rietveld analysis was applied to obtain cell parameters, atomic positions and atomic displacement factors and compared with literature available. Also, the quantification of phases was performed for the different contents of Gd{sub 2}O{sub 3} in the system. Finally, mean crystallite sizes were determined and correlated with the weight fraction of the phases. (author)

  7. Crystal structure, thermal behavior, vibrational spectroscopy and ...

    Indian Academy of Sciences (India)

    64

    A single crystal was carefully selected under polarizing microscope and .... properties of our compound using infrared absorption and Raman scattering. ... pics in Raman at 1762 and 1782 cm-1 are assigned to the δ(HOH) mode of the water ...

  8. Formation of structured nanophases in halide crystals

    Czech Academy of Sciences Publication Activity Database

    Kulveit, Jan; Demo, Pavel; Polák, Karel; Sveshnikov, Alexey; Kožíšek, Zdeněk

    2013-01-01

    Roč. 5, č. 6 (2013), s. 561-564 ISSN 2164-6627 R&D Projects: GA ČR GAP108/12/0891 Institutional support: RVO:68378271 Keywords : halide crystals * nucleation Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.aspbs.com/asem.html#v5n6

  9. Solvothermal syntheses, crystal structures, optical and thermal ...

    Indian Academy of Sciences (India)

    compounds 1–3 exhibit optical band gaps between 2.06 and 2.35 eV. Keywords. .... under a nitrogen stream of 100 mL min. −1 . 2.3 X-ray diffraction. Single-crystal ..... Liu G N, Guo G C, Wang M S, Cai L Z and Huang J S. 2010 Five dimeric ...

  10. The crystal structure of tRNA

    Indian Academy of Sciences (India)

    Madhu

    of yeast alanine tRNA by Robert Holley's group at Cornell. University ... decode nonsense codons) with John Smith and Brenner. However, my ... tRNA from 10 g of unfractionated tRNA. ... tRNA crystals were, in fact, protein (Hendrikson et al.

  11. Hydrothermal syntheses and single crystal structural ...

    Indian Academy of Sciences (India)

    Unknown

    Colourless. 84 lined stainless steel bomb. After heating in a pro- grammable oven at the respective temperatures and autogenous pressures for the notified time scale, cooling was carried out on a ramp of 10°C/h to room temperature. The crystals were collected by filtration, washed with, deionized water followed by diethyl-.

  12. Construction of crystal structure prototype database: methods and applications

    International Nuclear Information System (INIS)

    Su, Chuanxun; Lv, Jian; Wang, Hui; Wang, Yanchao; Ma, Yanming; Li, Quan; Zhang, Lijun

    2017-01-01

    Crystal structure prototype data have become a useful source of information for materials discovery in the fields of crystallography, chemistry, physics, and materials science. This work reports the development of a robust and efficient method for assessing the similarity of structures on the basis of their interatomic distances. Using this method, we proposed a simple and unambiguous definition of crystal structure prototype based on hierarchical clustering theory, and constructed the crystal structure prototype database (CSPD) by filtering the known crystallographic structures in a database. With similar method, a program structure prototype analysis package (SPAP) was developed to remove similar structures in CALYPSO prediction results and extract predicted low energy structures for a separate theoretical structure database. A series of statistics describing the distribution of crystal structure prototypes in the CSPD was compiled to provide an important insight for structure prediction and high-throughput calculations. Illustrative examples of the application of the proposed database are given, including the generation of initial structures for structure prediction and determination of the prototype structure in databases. These examples demonstrate the CSPD to be a generally applicable and useful tool for materials discovery. (paper)

  13. Construction of crystal structure prototype database: methods and applications.

    Science.gov (United States)

    Su, Chuanxun; Lv, Jian; Li, Quan; Wang, Hui; Zhang, Lijun; Wang, Yanchao; Ma, Yanming

    2017-04-26

    Crystal structure prototype data have become a useful source of information for materials discovery in the fields of crystallography, chemistry, physics, and materials science. This work reports the development of a robust and efficient method for assessing the similarity of structures on the basis of their interatomic distances. Using this method, we proposed a simple and unambiguous definition of crystal structure prototype based on hierarchical clustering theory, and constructed the crystal structure prototype database (CSPD) by filtering the known crystallographic structures in a database. With similar method, a program structure prototype analysis package (SPAP) was developed to remove similar structures in CALYPSO prediction results and extract predicted low energy structures for a separate theoretical structure database. A series of statistics describing the distribution of crystal structure prototypes in the CSPD was compiled to provide an important insight for structure prediction and high-throughput calculations. Illustrative examples of the application of the proposed database are given, including the generation of initial structures for structure prediction and determination of the prototype structure in databases. These examples demonstrate the CSPD to be a generally applicable and useful tool for materials discovery.

  14. Electronic and magnetic structures of GdS layers investigated by first principle and series expansions calculations

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco)

    2014-04-01

    Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full Potential Linear Augmented Plane Wave (FLAPW) method within GGA+U approximation, are performed to investigate both electronic and magnetic properties of the GdS layers. Polarized spin and spin–orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent Gd layers. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for the High Temperature Series Expansions (HTSEs) calculations to compute other magnetic parameters. Using the Heisenberg model, the exchange interactions between the magnetic atoms Gd–Gd in the same layer and between the magnetic atoms in the adjacent bilayers are estimated. This estimate is obtained using the antiferromagnetic and ferromagnetic energies computed by abinitio calculations for GdS layers. The High Temperature Series Expansions (HTSEs) of the magnetic susceptibility of GdS with antiferromagnetic moment (m{sub Gd}) is given up to sixth order series versus of (J{sub 11}(Gd–Gd)/k{sub B}T). The Néel temperature T{sub N} is obtained by mean field theory and by HTSEs of the magnetic susceptibility series using the Padé approximant method. The critical exponent γ associated with the magnetic susceptibility is calculated for GdS layers. - Highlights: • Electronic and magnetic properties of GdS are investigated using the ab initio calculations. • Obtained data from abinitio calculations are used as input for HTSEs to compute other magnetic parameters. • Néel temperature and critical exponent are deduced using HTSE method.

  15. Electronic and magnetic structures of GdS layers investigated by first principle and series expansions calculations

    International Nuclear Information System (INIS)

    Masrour, R.; Hlil, E.K.; Hamedoun, M.; Benyoussef, A.

    2014-01-01

    Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full Potential Linear Augmented Plane Wave (FLAPW) method within GGA+U approximation, are performed to investigate both electronic and magnetic properties of the GdS layers. Polarized spin and spin–orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent Gd layers. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for the High Temperature Series Expansions (HTSEs) calculations to compute other magnetic parameters. Using the Heisenberg model, the exchange interactions between the magnetic atoms Gd–Gd in the same layer and between the magnetic atoms in the adjacent bilayers are estimated. This estimate is obtained using the antiferromagnetic and ferromagnetic energies computed by abinitio calculations for GdS layers. The High Temperature Series Expansions (HTSEs) of the magnetic susceptibility of GdS with antiferromagnetic moment (m Gd ) is given up to sixth order series versus of (J 11 (Gd–Gd)/k B T). The Néel temperature T N is obtained by mean field theory and by HTSEs of the magnetic susceptibility series using the Padé approximant method. The critical exponent γ associated with the magnetic susceptibility is calculated for GdS layers. - Highlights: • Electronic and magnetic properties of GdS are investigated using the ab initio calculations. • Obtained data from abinitio calculations are used as input for HTSEs to compute other magnetic parameters. • Néel temperature and critical exponent are deduced using HTSE method

  16. Chemical bonding and magnetic properties of gadolinium (Gd) substituted cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Puli, Venkata Sreenivas, E-mail: vspuli@utep.edu [Department of Mechanical Engineering, University of Texas, El Paso, TX 79968 (United States); Adireddy, Shiva [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118 (United States); Ramana, C.V. [Department of Mechanical Engineering, University of Texas, El Paso, TX 79968 (United States)

    2015-09-25

    Graphical abstract: Room temperature Raman spectra of CoFe{sub 2−x}Gd{sub x}O{sub 4} (CFGO, x = 0.0–0.3) compounds as a function of wavenumber (cm{sup −1}). - Highlights: • Gd substituted ferrites were synthesized under controlled concentration. • Gd ion induced lattice dynamical changes are significant. • Enhanced magnetization is observed upon Gd-incorporation in cobalt ferrite. • A correlation between lattice dynamics and magnetic properties is established. - Abstract: Polycrystalline gadolinium (Gd) substituted cobalt ferrites (CoFe{sub 2−x}Gd{sub x}O{sub 4}; x = 0–0.3, referred to CFGO) ceramics have been synthesized by solid state reaction method. Chemical bonding, crystal structure and magnetic properties of CFGO compounds have been evaluated as a function of Gd-content. X-ray diffraction (XRD) and Raman spectroscopic analyses confirmed the formation of inverse spinel cubic structure. However, a secondary ortho-ferrite phase (GdFeO{sub 3}) nucleates for higher values of Gd-content. A considerable increase in the saturation magnetization has been observed upon the initial substitution of Gd (x = 0.1). The saturation magnetization drastically decreases at higher Gd content (x ⩾ 0.3). No contribution from ortho-ferrite GdFeO{sub 3} phase is noted to the magnetic properties. The increase in the magnetic saturation magnetization is attributed to the higher magnetic moment of Gd{sup 3+} (4f{sup 7}) residing in octahedral sites is higher when compared to that of Fe{sup 3+} (3d{sup 5}) and as well due to the migration of Co{sup 2+} (3d{sup 7}) ions from the octahedral to the tetrahedral sites with a magnetic moment aligned anti-parallel to those of rare earth (RE{sup 3+}) ions in the spinel lattice. Increase in coercivity with increase in Gd{sup 3+} is content is attributed to magnetic anisotropy in the ceramics.

  17. Air stability and magnetic properties of GdN, TiN, and (Gd,Ti)N nanoparticles

    International Nuclear Information System (INIS)

    Si Pingzhan; Choi, C. J.; Tegus, O.; Brueck, E.; Geng, D. Y.; Zhang, Z. D.

    2008-01-01

    GdN, TiN, and (Gd,Ti)N nanoparticles were prepared by arc evaporating Gd, Ti, and Gd-Ti alloys in N 2 , respectively. Most of these nanoparticles show narrow size distribution with average diameter of 20 nm. Shell/core structure was observed in the (Gd,Ti)N nanoparticles, in which the shell was formed by surface reaction with air. (Gd,Ti)N nanoparticles are more stable than GdN nanoparticles in air due partially to the formation of the protective shell. The Curie temperature of GdN nanoparticles is lower than that of the bulk GdN. Both GdN and (Gd, Ti)N nanoparticles are difficult to reach magnetic saturation and show zero coercivity

  18. Magnetic field effect on Gd2(MoO4)3 domain structure formation in the phase transformation range

    International Nuclear Information System (INIS)

    Flerova, S.A.; Tsinman, I.L.

    1987-01-01

    The behaviour of ferroelastic-ferroelectric domain structure of gadolinium molybdate crystal (GMO)during its formation in the magnetic field in the vicinity of phase transformation is studied.It is shown that the formation of domain structure in the presence of a temperature gradient occurs in the field of mechanical stresses whose mainly stretching effect is concentrated near phase boundaries.The magnetic field intensifies summary mechanical stresses where a domain structure in a ferroelectric phase is formed due to interaction with the elements of inhomogeneous and differently oriented currents near phase boundaries

  19. Crystal structure of actinide metals at high compression

    International Nuclear Information System (INIS)

    Fast, L.; Soederlind, P.

    1995-08-01

    The crystal structures of some light actinide metals are studied theoretically as a function of applied pressure. The first principles electronic structure theory is formulated in the framework of density functional theory, with the gradient corrected local density approximation of the exchange-correlation functional. The light actinide metals are shown to be well described as itinerant (metallic) f-electron metals and generally, they display a crystal structure which have, in agreement with previous theoretical suggestions, increasing degree of symmetry and closed-packing upon compression. The theoretical calculations agree well with available experimental data. At very high compression, the theory predicts closed-packed structures such as the fcc or the hcp structures or the nearly closed-packed bcc structure for the light actinide metals. A simple canonical band picture is presented to explain in which particular closed-packed form these metals will crystallize at ultra-high pressure

  20. The crystal structure of the phosphatidylinositol 4-kinase IIalpha

    Czech Academy of Sciences Publication Activity Database

    Bäumlová, Adriana; Chalupská, Dominika; Rozycki, B.; Jovic, M.; Wisniewski, E.; Klíma, Martin; Dubánková, Anna; Kloer, D. P.; Nencka, Radim; Balla, T.; Bouřa, Evžen

    2015-01-01

    Roč. 22, č. 1 (2015), s. 5 ISSN 1211-5894. [Discussions in Structural Molecular Biology. Annual Meeting of the Czech Society for Structural Biology /13./. 19.03.2015-21.03.2015, Nové Hrady] EU Projects: European Commission(XE) 333916 - STARPI4K Institutional support: RVO:61388963 Keywords : PI4K IIalpha * crystal structure Subject RIV: CE - Biochemistry

  1. Synthesis, structural characterization, luminescent properties and theoretical study of three novel lanthanide metal-organic frameworks of Ho(III), Gd(III) and Eu(III) with 2,5-thiophenedicarboxylate anion

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Lippy F. [Instituto de Química, Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20550-013 (Brazil); Correa, Charlane C. [Departamento de Química-ICE, Universidade Federal de Juiz de Fora, Juiz de Fora-MG, 36036-330 (Brazil); Ribeiro, Sidney J.L.; Santos, Molíria V. dos [Institute of Chemistry, São Paulo State University − UNESP, CP 355 Araraquara-SP 14801-970 Brazil (Brazil); Dutra, José Diogo L.; Freire, Ricardo O. [Pople Computational Chemistry Laboratory, Departamento de Química, Universidade Federal de Sergipe, São Cristóvão-SE 49100-000 (Brazil); Machado, Flávia C., E-mail: flavia.machado@ufjf.edu.br [Departamento de Química-ICE, Universidade Federal de Juiz de Fora, Juiz de Fora-MG, 36036-330 (Brazil)

    2015-07-15

    In this paper, the synthesis of three new metal-organic frameworks of lanthanides (LnMOFs) ([Ln{sub 2}(2,5-tdc){sub 3}(dmso){sub 2}]·H{sub 2}O){sub n} (Ln=Ho (1); Gd (2); Eu (3); 2,5-tdc=2,5-thiophenedicarboxylate anion; dmso=dimethylsulfoxide), and their complete characterization, including single crystal X-ray diffraction, FTIR spectroscopy and thermogravimetric analysis are reported. In especial, photophysical properties of Eu(III) complex have been studied in detail via both theoretical and experimental approaches. Crystal structure of (1) reveals that each lanthanide ion is seven-coordinated by oxygen atoms in an overall distorted capped trigonal – prismatic geometry. The 2,5-tdc{sup 2−} ligands connect four Ln(III) centers, adopting (κ{sup 1}–κ{sup 1})–(κ{sup 1}–κ{sup 1})–μ{sub 4} coordination mode, generating an 8-connected uninodal 3D network. In addition, theoretical studies for Eu(III) complex were performed using the Sparkle model for lanthanide complexes. - Graphical abstract: Three new metal-organic frameworks of lanthanides (LnMOFs) ([Ln{sub 2}(2,5-tdc){sub 3}(dmso){sub 2}]·H{sub 2}O){sub n} (Ln=Ho (1); Gd (2); Eu (3); 2,5-tdc=2,5-thiophenedicarboxylate anion; dmso=dimethylsulfoxide), were synthesized and their complete characterization, including single crystal X-ray diffraction, FTIR spectroscopy and thermogravimetric analysis are reported. In especial, photophysical properties of Eu(III) complex have been studied in detail via both theoretical and experimental approaches. - Highlights: • Three new LnMOFs were synthesized and fully characterized. • Ho{sup 3+}, Gd{sup 3+} and Eu{sup 3+} complexes photoluminescence properties were investigated. • Theoretical approaches for Eu{sup 3+} complex luminescence has been performed. • An energy level diagram is used to establish the ligand-to-metal energy transfer. • These metal−organic frameworks can act as light conversion molecular devices.

  2. Photophysical electronic structure of double-perovskites A{sub 2}GdTaO{sub 6} (A = Ba and Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Binita, E-mail: ghosh.binita@gmail.com [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Dutta, Alo [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Shannigrahi, Santiranjan [Institute of Materials Research and Engineering, Agency for Science Technology and Research, 3 Research Link, Singapore 117602 (Singapore); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India)

    2015-11-05

    X-ray photoemission spectroscopy (XPS) measurements of double perovskite oxides, Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} are performed in the energy window of 0–1300 eV. Density functional theory calculations are initiated with the Vienna ab initio Simulation Package to understand the electronic structure of the systems. The calculated DOS has been compared with the experimental valence band XPS spectra. It has been observed that the Ta-5d and O-2p states are hybridized in the valence band. The chemical shifts of these compounds suggest a mixed ionic and covalent character of the bonds, which has been used to explain the electrical conduction mechanism of the systems. The calculated ratio of the spin-orbit interaction energy for Ba 3d and 4d states matches well with the observed experimental results. - Highlights: • DFT calculations of Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} have been performed with VASP. • XPS measurements are performed in the energy window of 0–1300 eV. • The calculated DOS has been compared with the valence band XPS spectra. • Chemical shifts from XPS spectra have been used to explain the conduction mechanism.

  3. Structure of initial crystals formed during human amelogenesis

    Science.gov (United States)

    Cuisinier, F. J. G.; Voegel, J. C.; Yacaman, J.; Frank, R. M.

    1992-02-01

    X-ray diffraction analysis revealed only the existence of carbonated hydroxyapatite (c.HA) during amelogenesis, whereas conventional transmission electron microscopy investigations showed that developing enamel crystals have a ribbon-like habit. The described compositional changes could be an indication for the presence of minerals different from c.HA. However, the absence of identification of such a mineral shows the need of studies by high resolution electron microscopy (HREM) of initial formed human enamel crystals. We demonstrate the existence of two crystal families involved in the early stages of biomineralization: (a) nanometer-size particles which appeared as a precursor phase; (b) ribbon-like crystals, with a structure closely related to c.HA, which by a progressive thickening process tend to attain the mature enamel crystal habit.

  4. Comment on 'Magnetic Structure of Gd2Ti2O7'

    International Nuclear Information System (INIS)

    Stewart, John Ross; Ehlers, Georg; Wills, A.S.; Bramwell, S.T.; Gardner, Jason

    2012-01-01

    M. W. Long and collaborators ( Phys. Rev. B 83 054422 (2011)] recently proposed magnetic structures for gadolinium titanate that differ from those previously reported by us ( J. R. Stewart, G. Ehlers, A. S. Wills, S. T. Bramwell and J. S. Gardner J. Phys.: Condens. Matter 16 L321 (2004)]. In this Comment, we show that the calculated structure factors, S(Q), of the newly proposed models are inconsistent with our neutron powder diffraction data. Long and colleagues were led to reconsider the magnetic structure of gadolinium titanate on the basis of a number of theoretical and experimental assumptions. We argue that these assumptions have no basis in fact and conclude that they provide no reason to doubt our published magnetic structures.

  5. Synthesis, structure and magnetic properties of Fe-Gd nanocapsules coated with B2O3/H3BO3 and Fe3BO5+GdBO3

    International Nuclear Information System (INIS)

    Si, P.Z.; Brueck, E.; Zhang, Z.D.; Tegus, O.; Buschow, K.H.J.; Zhang, W.S.; Klaasse, J.C.P.; Boer, F.R. de

    2004-01-01

    Nanocapsules consisting of B 2 O 3 /H 3 BO 3 encapsulating Fe-Gd cores have been synthesized by an arc-discharge process using metal-boron alloys as cathode. Most of the nanocapsules have a well-constructed shell/core structure with a uniform B 2 O 3 /H 3 BO 3 shell. Heat-treatment induces reactions between the shell and the core, resulting in the formation of a Fe 3 BO 5 +GdBO 3 matrix embedded with Fe nanoparticles, reduction of the metallic-core size and decrease of the blocking temperature T B . Above T B , the magnetization curves plotted vs. H/T overlap and show zero coercivity. Below T B , the coercivity shows a linear dependence when plotted vs. T 1/2 . However, the coercivity-T 1/2 curve below 60 K has a different slope from that above 60 K, indicating the existence of two different magnetic phases in the nanocapsules. Different from bulk Fe 3 BO 5 , nanoscale Fe 3 BO 5 particles have a lower transition temperature to the weak-ferromagnetic state, and magnetic hysteresis is absent due to size effects

  6. Electronic structure and magnetic properties of GdM2 compounds

    International Nuclear Information System (INIS)

    Kantorovich, S.S.

    2003-01-01

    The formation of chain-like aggregates is studied theoretically on the basis of the model bidisperse ferrofluid, consisting of two fractions of small and large particles. Various topological structures of chains, containing particles of both fractions, are considered. The equilibrium chain distribution is obtained with the help of density functional approach. This model results are evidence of the fact that in spite of the small particle magnetic moment value being low, the presence of the latter fraction exerts a considerable influence on the ferrofluid microstructure. The chain aggregate structure appearance probabilities are calculated and the phase diagram allowing one to find the most probable chain structure in real ferrofluid, knowing only the continuous particle size distribution, is built

  7. Crystal structure and optical properties of silver nanorings

    Science.gov (United States)

    Zhou, Li; Fu, Xiao-Feng; Yu, Liao; Zhang, Xian; Yu, Xue-Feng; Hao, Zhong-Hua

    2009-04-01

    We report the polyol synthesis and crystal structure characterization of silver nanorings, which have perfect circular shape, smooth surface, and elliptical wire cross-section. The characterization results show that the silver nanorings have well-defined crystal of singly twinned along the whole ring. The spatial distribution of the scattering of a silver nanoring with slanted incidence reveals the unique focus effect of the nanoring, and the focus scattering varies with the incident wavelength. The silver nanorings with perfect geometry and well-defined crystal have potential applications in nanoscaled photonics, plasmonic devices, and optical manipulation.

  8. Crystal structures of two thiacalix[4]arene derivatives anchoring four ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The crystal structures of two thiacalixarene derivatives anchoring thiadiazole functional groups at lower rim, C60H72O4S12N8 (1), C64H80O4S12N8 (2), have been determined by single crystal X-ray diffraction. The thiacalix[4]arene framework in both 1 and 2 adopts the 1,3-alternate conformation. Com- pound 1 ...

  9. Crystal structure of ethyl 2,4-dichloroquinoline-3-carboxylate

    Directory of Open Access Journals (Sweden)

    Alberto Cabrera

    2015-12-01

    Full Text Available In the crystal structure of the title compound, C12H9Cl2NO2, the mean planes through the quinoline and carboxylate groups have r.m.s. deviations of 0.006 and 0.021 Å, respectively, and form a dihedral angle of 87.06 (19°. In the crystal, molecules are linked via very weak C—H...O hydrogen bonds, forming chains, which propagate along the c-axis direction.

  10. Isolation, crystallization and crystal structure determination of bovine kidney Na(+),K(+)-ATPase.

    Science.gov (United States)

    Gregersen, Jonas Lindholt; Mattle, Daniel; Fedosova, Natalya U; Nissen, Poul; Reinhard, Linda

    2016-04-01

    Na(+),K(+)-ATPase is responsible for the transport of Na(+) and K(+) across the plasma membrane in animal cells, thereby sustaining vital electrochemical gradients that energize channels and secondary transporters. The crystal structure of Na(+),K(+)-ATPase has previously been elucidated using the enzyme from native sources such as porcine kidney and shark rectal gland. Here, the isolation, crystallization and first structure determination of bovine kidney Na(+),K(+)-ATPase in a high-affinity E2-BeF3(-)-ouabain complex with bound magnesium are described. Crystals belonging to the orthorhombic space group C2221 with one molecule in the asymmetric unit exhibited anisotropic diffraction to a resolution of 3.7 Å with full completeness to a resolution of 4.2 Å. The structure was determined by molecular replacement, revealing unbiased electron-density features for bound BeF3(-), ouabain and Mg(2+) ions.

  11. Band structures and localization properties of aperiodic layered phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yan Zhizhong, E-mail: zzyan@bit.edu.cn [Department of Applied Mathematics, Beijing Institute of Technology, Beijing 100081 (China); Zhang Chuanzeng [Department of Civil Engineering, University of Siegen, D-57078 Siegen (Germany)

    2012-03-15

    The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.

  12. Crystal structure and thermal property of polyethylene glycol octadecyl ether

    International Nuclear Information System (INIS)

    Meng, Jie-yun; Tang, Xiao-fen; Li, Wei; Shi, Hai-feng; Zhang, Xing-xiang

    2013-01-01

    Highlights: ► The crystal structure of C18En for n ≥ 20 is a monoclinic system. ► Polyethylene glycol octadecyl ether crystallizes perfectly. ► The number of repeat units has significant effect on the melting, crystallizing temperature and enthalpy. ► The thermal stable temperature increases rapidly with increasing the number of repeat unit. - Abstract: The crystal structure, phase change property and thermal stable temperature (T d ) of polyethylene glycol octadecyl ether [HO(CH 2 CH 2 O) n C 18 H 37 , C18En] with various numbers of repeat units (n = 2, 10, 20 and 100) as phase change materials (PCMs) were investigated using temperature variable Fourier transformed infrared spectroscopy (FTIR), wide-angle X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). C18En crystallizes perfectly at 0 °C; and the crystal structure for n ≥ 20 is a monoclinic system. The number of repeat units has great effect on the phase change properties of C18En. The thermal stable temperature increases rapidly with increasing the number of repeat units. They approach to that of PEG-2000 as the number of repeat units is more than 10. T d increases rapidly with increasing the number of repeat units. C18En are a series of promising polymeric PCMs

  13. Study the effect of Gd{sup 3+} incorporation into nanocrystalline (Ni–Ti) substituted Mn–Zn ferrites on its structure and functional properties

    Energy Technology Data Exchange (ETDEWEB)

    Rady, K.E., E-mail: k_rady_2001@yahoo.com [Engineering Basic Sciences Department, Faculty of Engineering, Menoufia University, Shebin El-El, Kom (Egypt); Shams, M.S. [Department of Physics and Engineering Mathematics, Faculty of Electronic Engineering, Menoufia University, Menouf (Egypt)

    2017-03-15

    Ferrite samples with general chemical formula Mn{sub 0.9}Zn{sub 0.1}Ni{sub 0.05}Ti{sub 0.05}Gd{sub t}Fe{sub 1.9−t}O{sub 4}; (0.0≤ t≤0.05; step 0.01) were prepared using solid state reaction technique and the effect of Gd{sup 3+} ions incorporation on its physical properties has been studied. From the obtained results, XRD analysis reveals that the samples have a cubic spinel single phase structure for 0.0≤ t≤0.02; while for t≥0.03 a small peak of secondary phase (Gd{sub 3}Fe{sub 5}O{sub 12}) appears and becomes more noticeable with increasing Gd content. The lattice parameter (a) of the prepared samples was found to be initially increases and then decreases with increasing Gd content which may be attributed to the difference in the ionic radii of the cations involved and the solubility limit of Gd{sup 3+} ions. The crystallite size of the samples was estimated using Scherrer's equation and ranged from 96 nm to 107 nm. A vibrating sample magnetometer (VSM) was used at room temperature in order to study the effect of Gd content on the magnetic hysteresis parameters of the prepared ferrites such as saturation magnetization and coercivity. DC molar magnetic susceptibility (χ{sub M}) for the prepared samples was measured using Faraday's method as a function of temperature and the Curie temperature was calculated from the magnetic susceptibility measurements. Also the DC resistivity of the samples was measured at room temperature. The obtained results show that, the substitution by Gd{sup 3+} ions improves the electrical properties of the samples by increasing it DC electrical resistivity by 118% and consequently decreases it eddy current loss while the saturation magnetization slightly decreased by 14% only. The sample of t=0.01 shows a high dc magnetic susceptibility, high saturation magnetization (43.1 emu/g), high electric resistivity 12×10{sup 3} Ω.m and high Curie temperature (496 K), which is useful in some technological applications such

  14. Crystal structure of 4-methylsulfanyl-2-phenylquinazoline

    Directory of Open Access Journals (Sweden)

    Mohammed B. Alshammari

    2014-08-01

    Full Text Available In the title compound, C15H12N2S, the methylthioquinazoline group is planar with the methyl C displaced by only 0.116 (3 Å from the plane of the quinazoline moiety. The dihedral angle between the phenyl ring and the quinazoline ring system is 13.95 (5°. In the crystal, each molecule is linked by π–π stacking between to two adjacent inversion-related molecules. On one side, the inverted quinazoline groups interact with a centroid–centroid distance of 3.7105 (9 Å. On the other side, the quinazoline group interacts with the pyrimidine and phenyl rings of the second neighbour with centroid–centroid distances of 3.5287 (8 and 3.8601 (9 Å, respectively.

  15. Crystal structure of rubidium peroxide ammonia disolvate

    Directory of Open Access Journals (Sweden)

    Tobias Grassl

    2017-02-01

    Full Text Available The title compound, Rb2O2·2NH3, has been obtained as a reaction product of rubidium metal dissolved in liquid ammonia and glucuronic acid. As a result of the low-temperature crystallization, a disolvate was formed. To our knowledge, only one other solvate of an alkali metal peroxide is known: Na2O2·8H2O has been reported by Grehl et al. [Acta Cryst. (1995, C51, 1038–1040]. We determined the peroxide bond length to be 1.530 (11 Å, which is in accordance with the length reported by Bremm & Jansen [Z. Anorg. Allg. Chem. (1992, 610, 64–66]. One of the ammonia solvate molecules is disordered relative to a mirror plane, with 0.5 occupancy for the corresponding nitrogen atom.

  16. Crystal growth and characterization of Tm doped mixed rare-earth aluminum perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Totsuka, Daisuke, E-mail: totsuka@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Nihon Kessho Kogaku Co., Ltd., 810-5 Nobe-cho, Tatebayashi, Gunma 374-0047 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Sugiyama, Makoto; Fujimoto, Yutaka; Yokota, Yuui [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer (Lu{sub x}Gd{sub y}Y{sub 0.99-x-y}Tm{sub 0.01})AP single crystals were grown by the {mu}-PD method. Black-Right-Pointing-Pointer The grown crystals were single phase with perovskite structure (Pbnm). Significant segregation of Lu and Gd was detected in the growth direction. Black-Right-Pointing-Pointer Some absorption bands due to Tm{sup 3+}, Gd{sup 3+} and color centers were exhibited. Black-Right-Pointing-Pointer Radioluminescence spectra showed several emission peaks ascribed to Tm{sup 3+} and Gd{sup 3+}. -- Abstract: In this work, we present results of structural characterization and optical properties including radio luminescence of (Lu{sub x}Gd{sub y}Y{sub 0.99-x-y}Tm{sub 0.01})AP single crystal scintillators for (x, y) = (0.30, 0.19), (0, 0.19) and (0, 0) grown by the micro-pulling-down ({mu}-PD) method. The grown crystals were single phase materials with perovskite structure (Pbnm) as confirmed by XRD and had a good crystallinity. The distribution of the crystal constituents in growth direction was evaluated, and significant segregation of Lu and Gd was detected in (Lu{sub 0.30}Gd{sub 0.19}Y{sub 0.50}Tm{sub 0.01})AP sample. The crystals demonstrated 70% transmittance in visible wavelength range and some absorption bands due to Tm{sup 3+}, Gd{sup 3+} and color centers were exhibited in 190-900 nm. The radioluminescence measurement under X-ray irradiation demonstrated several emission peaks ascribed to 4f-4f transitions of Tm{sup 3+} and Gd{sup 3+}. The ratio of emission intensity in longer wavelength range was increased when Y was replaced by Lu or Gd.

  17. Synthesis and characterization of the structural and magnetic properties of new uranium and copper-based silicides and germanides: study of the physical and hydridation properties of some compounds belonging to the Gd-Ni-X systems, where X = Ga, Al, Sn

    International Nuclear Information System (INIS)

    Pechev, St.

    1998-01-01

    Three novel phases, U 3 Cu 4 Si 4 , U 3 Cu 4 Ge 4 and UCuGe 1,77 , were prepared in the U - Cu - X (X = Si or Ge) ternary system. Their structural and magnetic properties were investigated. The magnetic structures of the first two compounds were determined by neutron diffraction. Structural and magnetic behaviour transitions occur as copper substitutes silicon atoms in the UCu x Si 2-x (0,28 ≤ x ≤ 0,96) solid solution. Thus, the structure of the compositions changes in the α-ThSi 2 (tetragonal) → AlB 2 (hexagonal) → Ni 2 In(hexagonal) sequence while a transition from a nonmagnetic to ferromagnetic then antiferromagnetic behaviour is observed. The magnetic properties of the different compositions are governed by a Kondo - RKKY -type interactions competition. Crystallographic disorder and magnetic frustrations are at the origin of a spin glass state between the ferro- and antiferromagnetic areas. The investigations of the GdNi 3 X 2 (X =Ga, Al, Sn) compounds revealed that their structural and magnetic properties are strongly dependent on the nature of the X element as well as the on thermal treatment. A CaCu 5 → HoNi 2,6 Ga 2,4 - type structure transition and a ferro - to antiferromagnetic behaviour evolution are favoured by the increase of the X - atom size. A commensurate modulated crystal structure (described also as a a HoNi 2,6 Ga 2,4 x a HoNi 2,6 Ga 2,4 x 2c HoNi 2,6 Ga 2,4 -type superstructure) has been observed for GdNi 3 Al 2 . Hydrogen absorption in Gd 3 Ni 6 Al 2 and GdNi 3 Al 2 weakens the strength of the magnetic interactions. (author)

  18. The crystal structure of urea nitrate

    NARCIS (Netherlands)

    Harkema, Sybolt; Feil, D.

    1969-01-01

    The structure of urea nitrate has been solved, by the use of three-dimensional X-ray data. Data were collected using Cu Ke and Mo K0~ radiations. The structure consists of layers with urea and nitrate groups held together by hydrogen bonds. The positions of all hydrogen atoms were found. The final R

  19. A crystal structure prediction enigma solved

    DEFF Research Database (Denmark)

    Hoser, Anna Agnieszka; Sovago, Ioana; Lanzac, A.

    2017-01-01

    The seemingly unpredictable structure of gallic acid monohydrate form IV has been investigated using accurate X-ray diffraction measurements at temperatures of 10 and 123 K. The measurements demonstrate that the structure is commensurately modulated at 10 K and disordered at higher temperatures...

  20. Solving Crystal Structures from Powder Diffraction Data

    DEFF Research Database (Denmark)

    Christensen, A. Nørlund; Lehmann, M. S.; Nielsen, Mogens

    1985-01-01

    High resolution powder data from both neutron and X-ray (synchrotron) sources have been used to estimate the possibility of direct structure determination from powder data. Two known structures were resolved by direct methods with neutron and X-ray data. With synchrotron X-ray data, the measured ...

  1. Study on the thermoluminescent properties of K2YF5 and K2GdF5 crystals doped with optically active trivalent ions for gamma and neutrons dosimetry

    International Nuclear Information System (INIS)

    Silva, Edna Carla da

    2008-01-01

    In this work, the thermoluminescent (TL) properties of both double potassium yttrium fluoride (K 2 YF 5 ) and double potassium gadolinium fluoride (K 2 GdF 5 ) crystals doped with optically active rare earth ions were investigated from the point of view of gamma and neutron dosimetry. Crystalline platelets with thickness of about 1 mm, synthesized under hydrothermal conditions, were irradiated in order to study TL sensitivity, as well as dose and energy response, reproducibility and fading, in terms of Ce 3+ , Tb 3+ , Dy 3+ , e Pr 3+ concentrations. The K 2 YF 5 crystals doped with 1.0 at por cent Dy 3+ have been found to have an excellent linear TL response to X and gamma photons, in the range of 0.01 to 10 mGy. The TL output is comparable to that of CaS0 4 :Mn dosemeters. The main peak at 130 deg C has been found to have a TL response for 41.1 keV X-ray energy 32 times higher than that for 662 keV gamma rays. This fact points out that the K 2 Y 0.99 Dy 0.01 F 5 crystals have great potential for X-rays diagnostic and/or industrial radiography. On the other hand, the K 2 GdF 5 crystals doped with 5.0 at por cent Dy 3+ have been found to have the better TL response for gamma and fast neutron radiation, among the dopants studied. For gamma fields the TL response was linear for doses ranging from 0.1 to 200 mGy. The TL peak around 200 deg C can be deconvoluted into four individual peaks, all of them with linear behavior. For fast neutron radiation produced by an 241 Am B e source, the TL responses for doses ranging from 0.6 to 12 mSv were also linear and comparable to that of commercial TLD-600, irradiated at same conditions. The TL emission due to neutrons was in the high temperature range, above 200 deg C. These results points out that K 2 Gd 0.95 Dy 0.05 F 5 crystals are good candidates for use in neutron dosimetry applications. (author)

  2. Thermal and optical properties of Tm{sup 3+}: Li{sub 6}Gd(BO{sub 3}){sub 3} crystal: A potential candidate for 1.83 {mu}m lasers

    Energy Technology Data Exchange (ETDEWEB)

    Ma Xinghua [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Key Laboratory of Materials Chemistry and Physics, Yangqiao West Road 155, Fuzhou, Fujian 350002 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Li Jianfu; Zhu Zhaojie; You Zhenyu; Wang Yan [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Key Laboratory of Materials Chemistry and Physics, Yangqiao West Road 155, Fuzhou, Fujian 350002 (China); Tu Chaoyang [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Key Laboratory of Materials Chemistry and Physics, Yangqiao West Road 155, Fuzhou, Fujian 350002 (China)], E-mail: tcy@fjirsm.ac.cn

    2008-10-15

    Single crystal of Tm{sup 3+}: Li{sub 6}Gd (BO{sub 3}){sub 3} was grown by the Czochralski method. The heat capacity was measured from 308 to 673 K. The absorption spectra of the crystal in three mutually perpendicular arbitrary directions were measured at room temperature. Based on the Judd-Ofelt theory and the spectra measured in three mutually perpendicular directions, the intensity parameters {omega}{sub t} (t=2, 4, 6), the line strengths, the oscillator strengths, the radiative rates, radiative lifetimes and fluorescent branching ratios were calculated. We calculated the emission cross-section by the reciprocity method and also obtained the gain cross-section.

  3. High-Q microwave resonators with a photonic crystal structure

    International Nuclear Information System (INIS)

    Schuster, M.

    2001-08-01

    The localisation of electromagnetic energy at a defect in a photonic crystal is similar to a well known effect employed to construct high-Q microwave resonators: In a whispering gallery (WHG-) mode resonator the high Q-factor is achieved by localisation of the electromagnetic field energy by total reflection inside a disk made of dielectric material. The topic of this work is to demonstrate, that WHG-like modes can exist in an air defect in a photonic crystal that extends over several lattice periods; and that a high-Q microwave resonator can be made, utilizing these resonant modes. In numerical simulations, the transmission properties of a photonic crystal structure with hexagonal lattice symmetry have been investigated with a transfer-matrix-method. The eigenmodes of a defect structure in a photonic crystal have been calculated with a quasi-3d finite element integration technique. Experimental results confirm the simulated transmission properties and show the existence of modes inside the band gap, when a defect is introduced in the crystal. Resonator measurements show that a microwave resonator can be operated with those defect modes. It was found out that the main losses of the resonator were caused by bad microwave properties of the used dielectric material and by metal losses on the top and bottom resonator walls. Furthermore, it turned out that the detection of the photonic crystal defect mode was difficult because of a lack of simulation possibilities and high housing mode density in the resonator. (orig.)

  4. Crystal-Size-Dependent Structural Transitions in Nanoporous Crystals: Adsorption-Induced Transitions in ZIF-8

    KAUST Repository

    Zhang, Chen

    2014-09-04

    © 2014 American Chemical Society. Understanding the crystal-size dependence of both guest adsorption and structural transitions of nanoporous solids is crucial to the development of these materials. We find that nano-sized metal-organic framework (MOF) crystals have significantly different guest adsorption properties compared to the bulk material. A new methodology is developed to simulate the adsorption and transition behavior of entire MOF nanoparticles. Our simulations predict that the transition pressure significantly increases with decreasing particle size, in agreement with crystal-size-dependent experimental measurements of the N2-ZIF-8 system. We also propose a simple core-shell model to examine this effect on length scales that are inaccessible to simulations and again find good agreement with experiments. This study is the first to examine particle size effects on structural transitions in ZIFs and provides a thermodynamic framework for understanding the underlying mechanism.

  5. Experimental evaluation of Gd3Al2Ga3O12:Ce (GAGG:Ce) single crystals coupled to a silicon photomultiplier (SiPM) under high gamma ray irradiation conditions

    Science.gov (United States)

    Metallinos, A.; Kefalidis, E.; Kandarakis, I.; David, S.

    2017-11-01

    Cerium (Ce) ion doped scintillators are of high interest in Medical Imaging systems and radiation monitoring devices, due to their very fast response and very good emission characteristics. In this study, a series of measurements regarding the energy resolution, photofraction, sensitivity, as well as the figure of merit, of Gd3Al2Ga3O12:Ce (GAGG:Ce) scintillator crystals, is presented. All GAGG:Ce crystals have a surface area of 3x3 mm2 with varying thicknesses, from 4 up to 20 mm (4, 5, 6, 8, 10, 15 and 20 mm). These crystals were exposed to γ radiation, using two different radioactive sources: 137Cs (0.662 MeV) and 60Co (1.173 MeV and 1.332 MeV). Each crystal was measured individually and was optically coupled to a KETEK PM3350 SiPM, an optical sensor with high gain, suitable to operate in room temperature. The digitization of the pulses was accomplished using CAEN DT5720 desktop digitizer and its corresponding digital pulse processing (DPP) firmware. Each measurement was performed in a light-tight box and had duration of 30 min. The best energy resolution value was measured for the GAGG:Ce crystal with dimensions 3x3x15mm3, equal to 3.9% at 1.332 MeV. Results were evaluated and compared to previous published data.

  6. Crystal structure of aspartame anhydrate from powder diffraction data. Structural aspects of the dehydration process of aspartame

    NARCIS (Netherlands)

    Guguta, C.; Meekes, H.L.M.; Gelder, R. de

    2006-01-01

    Aspartame has three pseudo-polymorphic forms, two hydrates and a hemi-hydrate, for which crystal structures were determined from single-crystal diffraction data. This paper presents the crystal structure of the anhydrate, which was obtained by dehydrating the hemi-hydrate. The crystal structure of

  7. Synthesis, crystal structure and biological activity of novel diester cyclophanes

    International Nuclear Information System (INIS)

    Zhang, Pengfei; Yang, Bingqin; Fang, Xianwen; Cheng, Zhao; Yang, Meipan

    2012-01-01

    A series of novel diester cyclophanes was synthesized by esterification of 1,2-benzenedicarbonyl chloride with eight different diols under high dilution conditions. The structures of the compounds were verified by elemental analysis, 1 H nuclear magnetic resonance (NMR), IR spectroscopy and high resolution mass spectrometry (HRMS). The crystal structures of two compounds were characterized by single crystal X-ray diffractometry (XRD). All the new cyclophanes were evaluated for biological activities and the results showed that some of these compounds have low antibacterial or antifungal activities (author)

  8. Synthesis, crystal structure and biological activity of novel diester cyclophanes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengfei; Yang, Bingqin; Fang, Xianwen; Cheng, Zhao; Yang, Meipan, E-mail: yangbq@nwu.edu.cn [Department of Chemistry, Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Northwest University, Shaanxi (China)

    2012-10-15

    A series of novel diester cyclophanes was synthesized by esterification of 1,2-benzenedicarbonyl chloride with eight different diols under high dilution conditions. The structures of the compounds were verified by elemental analysis, {sup 1}H nuclear magnetic resonance (NMR), IR spectroscopy and high resolution mass spectrometry (HRMS). The crystal structures of two compounds were characterized by single crystal X-ray diffractometry (XRD). All the new cyclophanes were evaluated for biological activities and the results showed that some of these compounds have low antibacterial or antifungal activities (author)

  9. Photonic crystals, light manipulation, and imaging in complex nematic structures

    Science.gov (United States)

    Ravnik, Miha; Å timulak, Mitja; Mur, Urban; Čančula, Miha; Čopar, Simon; Žumer, Slobodan

    2016-03-01

    Three selected approaches for manipulation of light by complex nematic colloidal and non-colloidal structures are presented using different own custom developed theoretical and modelling approaches. Photonic crystals bands of distorted cholesteric liquid crystal helix and of nematic colloidal opals are presented, also revealing distinct photonic modes and density of states. Light propagation along half-integer nematic disclinations is shown with changes in the light polarization of various winding numbers. As third, simulated light transmission polarization micrographs of nematic torons are shown, offering a new insight into the complex structure characterization. Finally, this work is a contribution towards using complex soft matter in optics and photonics for advanced light manipulation.

  10. On structure of some laminated crystals with organic molecules

    International Nuclear Information System (INIS)

    Volodina, G.F.; Ivanova, V.Ya.; Malinovskij, T.I.

    1982-01-01

    A survey is made of papers dealing with intercalation of organic molecules into crystals of dihalcogenides of some transition metals (TaS 2 , TiS 2 , NbS 2 , ZrS 2 , TaSe 2 ), variation of their structure and physical properties. Among the used intercalates ammonia, pyridine, aniline and other aromatic amines proved to be most satisfactory from the viewpoint of reaction rate and product stability. A possibility is discussed of intercalation into PbI 2 and CdI 2 crystals that are of the same structural type as dihalcogenides

  11. Systematic analysis of crystal and molecular structures

    Czech Academy of Sciences Publication Activity Database

    Hašek, Jindřich; Dohnálek, Jan

    2012-01-01

    Roč. 19, č. 2 (2012), s. 86-87 ISSN 1211-5894. [Struktura 2012. Kolokvium Krystalografické společnosti. 11.06.2012-14.06.2012, Klatovy] R&D Projects: GA ČR GA310/09/1407 Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : structure databases * structure-function relations * organic and inorganic materials Subject RIV: EE - Microbiology, Virology

  12. The Structural Evolution of (Gd, Y)Ba2Cu3Ox Tapes With Zr Addition Made by Metal Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lei, CH; Galstyan, E; Chen, YM; Shi, T; Liu, YH; Khatri, N; Liu, JF; Xiong, XM; Majkic, G; Selvamanickam, V

    2013-06-01

    Structural analysis of (Gd, Y) Ba2Cu3Ox tapes with Zr addition made by metal organic chemical vapor deposition has been conducted with transmission electron microscopy and X-ray diffraction. Zr content in the films was varied from 0 to 25% in the precursor. In all Zr-doped films, self-assembled nanocolumnar structures of BaZrO3 (BZO) were observed along the c-axis. The amount of BaZrO3 was found to increase steadily with Zr content. Additionally, planar BZO plates were found on the (001) plane of (Gd, Y) Ba2Cu3Ox film. The size and thickness of BZO plates were seen to increase with Zr doping level. Rare-earth copper oxide phases were observed to begin to emerge in the 20% Zr-doped film. Cross-sectional study of the interface between (Gd, Y)Ba2Cu3Ox and LaMnO3 cap layer revealed a thin discrete BZO layer on the LaMnO3 in the 20% Zr doped film.

  13. Structural and magnetic characterization of the new GdMn1-xFexO3 perovskite material

    International Nuclear Information System (INIS)

    Vasquez, J A Cardona; Téllez, D A Landínez; Rojas, J Roa; Collazos, C A

    2016-01-01

    In this paper we presents the synthesis process of the GdMn 1-x Fe x O 3 perovskite material by conventional solid state reaction method. Crystalline phase evolution during the synthesis was studied by X-ray Diffraction (XRD) in powder of the materials, observing that the chemical reaction of the precursor oxides was significant above 1000°C. Rietveld refinement of DRX patterns shows a perovskite structure with octahedral distortions (space group Pbnm, # 62) for studied values of x (0, 0.1 and 0.2). The degree of substitution generates an increasing tendency on lattice parameters a and c, while for b is decreasing just as for the volume of the unit cell. The effect of the change in the lattice parameters directly affects the octahedral distortions, ie, with increasing degree of substitution (increased parameter c) octahedra tend to arrange one above the other aligned with the c axis. Magnetization measurements as a function of temperature were performed above room temperature between 300K and 860K with an applied field of 20Oe and below room temperature in Field Cooling (FC) and Zero Field Cooling modes (ZFC) between 4.2K and 300K with an applied field of 200Oe. Magnetic behavior above room temperature is paramagnetic for used values of x, on the other hand at low temperatures (T<30K) magnetic phase transitions associated to the apparition of an antiferromagnetic phase are observed. In addition for x=0.1 the derivative of magnetization shows a peak around 31K, associated to the ferrimagnetic transition for this material. Curie-Weiss fit reveals the antiferromagnetic (ferrimagnetic) behavior of the materials, also shows that the configurations with x=0 and x=0.2 have an effective magnetic moment very similar to the reported value of undoped material, while for x=0.1 a higher value is observed confirming the ferrimagnetic behavior of this configuration. (paper)

  14. GD 358 - the demise of rotational splitting?

    International Nuclear Information System (INIS)

    Hill, J.A.

    1987-01-01

    Observations of GD 358 were obtained at the McDonald Observatory in 1982 and 1985 in order to determine its periods, stability, and rates of period change. The period structure could not be resolved, and the results indicate that GD 358 does not fit the rotational splitting model. It is suggested that if the changes in the amplitude spectra of GD 358 are due to beating of stable modes, then the number of modes must be large. 7 references

  15. Photonics of liquid-crystal structures: A review

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S. P., E-mail: palto@online.ru; Blinov, L M; Barnik, M I; Lazarev, V V; Umanskii, B A; Shtykov, N M [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2011-07-15

    The original results of studies of the electro-optical and laser effects which have been performed at the Laboratory of Liquid Crystals of the Institute of Crystallography, Russian Academy of Sciences, over the last few years are reviewed. Cholesteric liquid crystals as vivid representatives of photonic structures and their behavior in an electric field are considered in detail. The formation of higher harmonics in the periodic distribution of the director field in a helical liquid crystal structure and, correspondingly, the new (anharmonic) mode of electro-optical effects are discussed. Another group of studies is devoted to bistable light switching by an electric field in chiral nematics. Polarization diffraction gratings controlled by an electric field are also considered. The results of studies devoted to microlasers on various photonic structures with cholesteric and nematic liquid crystals are considered in detail. Particular attention is given to the new regime: leaky-mode lasing. Designs of liquid crystal light amplifiers and their polarization, field, and spectral characteristics are considered in the last section.

  16. Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru1−xRexSr2GdCu2Oy

    International Nuclear Information System (INIS)

    Corredor, L.T.; Albino Aguiar, J.; Landínez Téllez, D.A.; Pureur, P.; Mesquita, F.; Roa-Rojas, J.

    2015-01-01

    Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr 2 GdCu 2 O 8 . • We synthesized the doped compound Rui x Re x Sr 2 GdCu 2 O y , for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru 1−x Re x Sr 2 GdCu 2 O y ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr 2 GdRu 1−x Re x O y , which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO 2 (magnetic) and CuO 2 (superconductor) sub-lattices can clearly be observed

  17. Influence of annealing temperature on structural and optical properties of SiO{sub 2}:RE{sub 2}O{sub 3} [RE = Y, Gd] powder

    Energy Technology Data Exchange (ETDEWEB)

    Ahlawat, Rachna, E-mail: rachnaahlawat2003@yahoo.com

    2015-07-25

    Highlights: • Sol–gel process is used to obtain spherical nanocrystallites of SiO{sub 2}:RE{sub 2}O{sub 3} [RE = Y, Gd] powder. • Effect of four steps annealing is studied on micro strain, nanocrystallite size and dislocation density. • Optical properties are examined by absorption spectra and PL. • SiO{sub 2}:RE{sub 2}O{sub 3} [RE = Y, Gd] binary oxides are promising materials for high temperature structural applications. - Abstract: SiO{sub 2}:RE{sub 2}O{sub 3} [RE = Y, Gd] powder were prepared by wet chemical technique and the prepared binary oxides annealed at 500 °C and 900 °C. The crystalline structure, phase transformation, and surface morphologies of as-prepared and annealed samples were investigated by XRD and TEM. The normal transmission was measured using FTIR spectroscopy. Optical properties have been studied with UV–Vis spectroscopy and PL study. XRD results shows that the as prepared samples of SiO{sub 2}:RE{sub 2}O{sub 3} [RE = Y, Gd] powder has mixed phases of RE(NO{sub 3}){sub 3} and Si(OH){sub 3}. However, cubic rare earth oxide phase alone is found for annealed samples. The strain values are calculated from W–H plot for annealed samples. TEM micrograph shows that the samples are composed of individual spherical nanocrystallites at 500 °C and aggregated nanocrystallites at 900 °C. From the UV–Vis spectra, it is found that the position of the absorption peak is shifted toward the higher wavelength side when annealing temperature is increased. In the PL spectra, the broad emission bands are observed between 570–600 nm and the presence of O–Si–O (silica) and metal oxide is confirmed by FTIR spectra.

  18. CRYSTAL STRUCTURE ANALYSIS OF A PUTATIVE OXIDOREDUCTASE FROM KLEBSIELLA PNEUMONIAE

    Energy Technology Data Exchange (ETDEWEB)

    Baig, M.; Brown, A.; Eswaramoorthy, S.; Swaminathan, S.

    2009-01-01

    Klebsiella pneumoniae, a gram-negative enteric bacterium, is found in nosocomial infections which are acquired during hospital stays for about 10% of hospital patients in the United States. The crystal structure of a putative oxidoreductase from K. pneumoniae has been determined. The structural information of this K. pneumoniae protein was used to understand its function. Crystals of the putative oxidoreductase enzyme were obtained by the sitting drop vapor diffusion method using Polyethylene glycol (PEG) 3350, Bis-Tris buffer, pH 5.5 as precipitant. These crystals were used to collect X-ray data at beam line X12C of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). The crystal structure was determined using the SHELX program and refi ned with CNS 1.1. This protein, which is involved in the catalysis of an oxidation-reduction (redox) reaction, has an alpha/beta structure. It utilizes nicotinamide adenine dinucleotide phosphate (NADP) or nicotine adenine dinucleotide (NAD) to perform its function. This structure could be used to determine the active and co-factor binding sites of the protein, information that could help pharmaceutical companies in drug design and in determining the protein’s relationship to disease treatment such as that for pneumonia and other related pathologies.

  19. Solving crystal structures with the symmetry minimum function

    International Nuclear Information System (INIS)

    Estermann, M.A.

    1995-01-01

    Unravelling the Patterson function (the auto-correlation function of the crystal structure) (A.L. Patterson, Phys. Rev. 46 (1934) 372) can be the only way of solving crystal structures from neutron and incomplete diffraction data (e.g. powder data) when direct methods for phase determination fail. The negative scattering lengths of certain isotopes and the systematic loss of information caused by incomplete diffraction data invalidate the underlying statistical assumptions made in direct methods. In contrast, the Patterson function depends solely on the quality of the available diffraction data. Simpson et al. (P.G. Simpson et al., Acta Crystallogr. 18 (1965) 169) showed that solving a crystal structure with a particular superposition of origin-shifted Patterson functions, the symmetry minimum function, is advantageous over using the Patterson function alone, for single-crystal X-ray data.This paper describes the extension of the Patterson superposition approach to neutron data and powder data by (a) actively using the negative regions in the Patterson map caused by negative scattering lengths and (b) using maximum entropy Patterson maps (W.I.F. David, Nature 346 (1990) 731). Furthermore, prior chemical knowledge such as bond lengths and angles from known fragments have been included. Two successful structure solutions of a known and a previously unknown structure (M. Hofmann, J. Solid State Chem., in press) illustrate the potential of this new development. ((orig.))

  20. PAK4 crystal structures suggest unusual kinase conformational movements.

    Science.gov (United States)

    Zhang, Eric Y; Ha, Byung Hak; Boggon, Titus J

    2018-02-01

    In order for protein kinases to exchange nucleotide they must open and close their catalytic cleft. These motions are associated with rotations of the N-lobe, predominantly around the 'hinge region'. We conducted an analysis of 28 crystal structures of the serine-threonine kinase, p21-activated kinase 4 (PAK4), including three newly determined structures in complex with staurosporine, FRAX486, and fasudil (HA-1077). We find an unusual motion between the N-lobe and C-lobe of PAK4 that manifests as a partial unwinding of helix αC. Principal component analysis of the crystal structures rationalizes these movements into three major states, and analysis of the kinase hydrophobic spines indicates concerted movements that create an accessible back pocket cavity. The conformational changes that we observe for PAK4 differ from previous descriptions of kinase motions, and although we observe these differences in crystal structures there is the possibility that the movements observed may suggest a diversity of kinase conformational changes associated with regulation. Protein kinases are key signaling proteins, and are important drug targets, therefore understanding their regulation is important for both basic research and clinical points of view. In this study, we observe unusual conformational 'hinging' for protein kinases. Hinging, the opening and closing of the kinase sub-domains to allow nucleotide binding and release, is critical for proper kinase regulation and for targeted drug discovery. We determine new crystal structures of PAK4, an important Rho-effector kinase, and conduct analyses of these and previously determined structures. We find that PAK4 crystal structures can be classified into specific conformational groups, and that these groups are associated with previously unobserved hinging motions and an unusual conformation for the kinase hydrophobic core. Our findings therefore indicate that there may be a diversity of kinase hinging motions, and that these may

  1. Crystal structure of clathrates of Hofmann dma-type

    International Nuclear Information System (INIS)

    NIshikiori, Sh.; Ivamoto, T.

    1999-01-01

    Seven new clathrates Cd(DMA) 2 Ni(CN) 4 ·xG (x=1, G=aniline, 2,3-xylidine, 2,4-xylidine, 2,5-xylidine, 2,6-xylidine, 3,5-xylidine, and x=2, G=2,4,6-trimethylaniline) of Hofmann type are synthesized by amine substitution for dimethylamine (DMA). On the base of x-ray diffraction data it is shown that geometry of guest molecule in cage-like hollow determines the structure of the host and crystal structure of clathrates. Two-dimension metallocomplex of the host of studied clathrates is characterized by elastic folded structure appearing as a result of angular deformation of bond between Cd atoms and host cyanide bridge. Guest molecule orientation is fixed by hydrogen bond. Structural elasticity of the host complex directs to differences in crystal structure of clathrates formed and to considerable variety of incorporated guests [ru

  2. Simulation and design of the photonic crystal microwave accelerating structure

    International Nuclear Information System (INIS)

    Song Ruiying; Wu Congfeng; He Xiaodong; Dong Sai

    2007-01-01

    The authors have derived the global band gaps for general two-dimensional (2D) photonic crystal microwave accelerating structures formed by square or triangular arrays of metal posts. A coordinate-space, finite-difference code was used to calculate the complete dispersion curves for the lattices. The fundamental and higher frequency global photonic band gaps were determined numerically. The structure formed by triangular arrays of metal posts with a missing rod at the center has advantages of higher-order-modes (HOM) suppression and main mode restriction under the condition of a/b<0.2. The relationship between the RF properties and the geometrical parameters have been studied for the 9.37 GHz photonic crystal accelerating structure. The Rs, Q, Rs/Q of the new structure may be comparable to the disk-loaded accelerating structure. (authors)

  3. Synthesis and crystal structures of three new benzotriazolylpropanamides

    Directory of Open Access Journals (Sweden)

    Donna S. Amenta

    2017-06-01

    Full Text Available The base-catalyzed Michael addition of 2-methylacrylamide to benzotriazole afforded 3-(1H-benzotriazol-1-yl-2-methylpropanamide, C10H12N4O (1, in 32% yield in addition to small amounts of isomeric 3-(2H-benzotriazol-2-yl-2-methylpropanamide, C10H12N4O (2. In a similar manner, 3-(1H-benzotriazol-1-yl-N,N-dimethylpropanamide, C11H14N4O (3, was prepared from benzotriazole and N,N-dimethylacrylamide. All three products have been structurally characterized by single-crystal X-ray diffraction. The crystal structures of 1 and 2 comprise infinite arrays formed by N—H...O and N—H...N bridges, as well as π–π interactions, while the molecules of 3 are aggregated to simple π-dimers in the crystal.

  4. Synthesis, Crystal Structure, Density Function Theory, Molecular ...

    African Journals Online (AJOL)

    Tropical Journal of Pharmaceutical Research ... Purpose: To determine the exact structure and antimicrobial activity of 2-(3-(4 phenylpiperazin-1-yl) ... Besides HOMO– LUMO energy gap was performed at B3LYP/6-31G (d,p) level of theory.

  5. Crystal engineering of ibuprofen compounds: From molecule to crystal structure to morphology prediction by computational simulation and experimental study

    Science.gov (United States)

    Zhang, Min; Liang, Zuozhong; Wu, Fei; Chen, Jian-Feng; Xue, Chunyu; Zhao, Hong

    2017-06-01

    We selected the crystal structures of ibuprofen with seven common space groups (Cc, P21/c, P212121, P21, Pbca, Pna21, and Pbcn), which was generated from ibuprofen molecule by molecular simulation. The predicted crystal structures of ibuprofen with space group P21/c has the lowest total energy and the largest density, which is nearly indistinguishable with experimental result. In addition, the XRD patterns for predicted crystal structure are highly consistent with recrystallization from solvent of ibuprofen. That indicates that the simulation can accurately predict the crystal structure of ibuprofen from the molecule. Furthermore, based on this crystal structure, we predicted the crystal habit in vacuum using the attachment energy (AE) method and considered solvent effects in a systematic way using the modified attachment energy (MAE) model. The simulation can accurately construct a complete process from molecule to crystal structure to morphology prediction. Experimentally, we observed crystal morphologies in four different polarity solvents compounds (ethanol, acetonitrile, ethyl acetate, and toluene). We found that the aspect ratio decreases of crystal habits in this ibuprofen system were found to vary with increasing solvent relative polarity. Besides, the modified crystal morphologies are in good agreement with the observed experimental morphologies. Finally, this work may guide computer-aided design of the desirable crystal morphology.

  6. On the formation and structural properties of hexagonal rare earth (Y, Gd, Dy, Er and Yb) disilicide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Geenen, F.A., E-mail: Filip.Geenen@UGent.be [Department of Solid-State Sciences, Ghent University, 9000 Gent (Belgium); Knaepen, W. [Department of Solid-State Sciences, Ghent University, 9000 Gent (Belgium); Demeulemeester, J. [Instituut voor Kern- en Stralingsfysica, KU Leuven, B-3001 Leuven (Belgium); De Keyser, K. [Department of Solid-State Sciences, Ghent University, 9000 Gent (Belgium); Jordan-Sweet, J.L.; Lavoie, C. [IBM T.J. Watson Research Center, Yorktown Heights, NY (United States); Vantomme, A. [Instituut voor Kern- en Stralingsfysica, KU Leuven, B-3001 Leuven (Belgium); Detavernier, C. [Department of Solid-State Sciences, Ghent University, 9000 Gent (Belgium)

    2014-10-25

    Highlights: • Solid-state reaction is studied of a several rare earth thin films with Si substrates. • h-GdSi{sub 1.7} grains have an epitaxial texture on both Si 1 0 0 and Si 1 1 1. • Formation temperature of h-RESi{sub 1.7} correlates with lattice parameter of the h-phase. - Abstract: A systematic study was performed of the solid state reaction between a 100 nm thick layer of a rare earth metal and a Si substrate. The solid state reaction of five different rare earth metals (yttrium, gadolinium, dysprosium, erbium and ytterbium) were studied by in situ X-ray diffraction measurements on Si(1 0 0), Si(1 1 1) and poly-Si. This allowed us to make a comparison between the different systems. The formation temperature of h-RESi{sub 1.7} are the highest on Si(1 1 1) and the lowest on poly-Si for all examined RE metals. Additionally, the texture of the Gd disilicide phase on Si(1 0 0) and Si(1 1 1) was investigated by means of ex situ pole figure measurements. The epitaxial relationship of hexagonal GdSi{sub 1.7} and orthorhombic GdSi{sub 2} on the different Si substrates is determined. The epitaxial growth is the strongest on Si(1 1 1)

  7. Synthesis and crystal structure analysis of uranyl triple acetates

    Energy Technology Data Exchange (ETDEWEB)

    Klepov, Vladislav V., E-mail: vladislavklepov@gmail.com [Institute for Energy and Climate Research (IEK-6), Forschungszentrum Jülich GmbH, 52428 Jülich (Germany); Department of Chemistry, Samara National Research University, 443086 Samara (Russian Federation); Serezhkina, Larisa B.; Serezhkin, Victor N. [Department of Chemistry, Samara National Research University, 443086 Samara (Russian Federation); Alekseev, Evgeny V., E-mail: e.alekseev@fz-juelich.de [Institute for Energy and Climate Research (IEK-6), Forschungszentrum Jülich GmbH, 52428 Jülich (Germany); Institut für Kristallographie, RWTH Aachen University, 52066 Aachen (Germany)

    2016-12-15

    Single crystals of triple acetates NaR[UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 3}·6H{sub 2}O (R=Mg, Co, Ni, Zn), well-known for their use as reagents for sodium determination, were grown from aqueous solutions and their structural and spectroscopic properties were studied. Crystal structures of the mentioned phases are based upon (Na[UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 3}){sup 2–} clusters and [R(H{sub 2}O){sub 6}]{sup 2+} aqua-complexes. The cooling of a single crystal of NaMg[UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 3}·6H{sub 2}O from 300 to 100 K leads to a phase transition from trigonal to monoclinic crystal system. Intermolecular interactions between the structural units and their mutual packing were studied and compared from the point of view of the stereoatomic model of crystal structures based on Voronoi-Dirichlet tessellation. Using this method we compared the crystal structures of the triple acetates with Na[UO{sub 2}(CH{sub 3}COO){sub 3}] and [R(H{sub 2}O){sub 6}][UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 2} and proposed reasons of triple acetates stability. Infrared and Raman spectra were collected and their bands were assigned. - Graphical abstract: Single crystals of uranium based triple acetates, analytical reagents for sodium determination, were synthesized and structurally, spectroscopically and topologically characterized. The structures were compared with the structures of compounds from preceding families [M(H{sub 2}O){sub 6})][UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 2} (M = Mg, Co, Ni, Zn) and Na[UO{sub 2}(CH{sub 3}COO){sub 3}]. Analysis was performed with the method of molecular Voronoi-Dirichlet polyhedra to reveal a large contribution of the hydrogen bonds into intermolecular interactions which can be a reason of low solubility of studied complexes.

  8. Structural relative stabilities and pressure-induced phase transitions for lanthanide trihydrides REH{sub 3} (RE=Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu)

    Energy Technology Data Exchange (ETDEWEB)

    Kong Bo, E-mail: kong79@yeah.net [National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900 (China); College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zhang Lin, E-mail: zhanglinbox@263.net [National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900 (China); Chen Xiangrong [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zeng Tixian [College of Physics and Electronic Information, China West Normal University, Nanchong 637002 (China); Cai Lingcang [National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900 (China)

    2012-06-15

    The structures, structural relative stabilities, pressure-induced phase transitions, and equations of state for lanthanide trihydrides REH{sub 3} (RE=Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu) are systematically studied using ab initio calculations under a core state model (CSM). The obtained ground-state parameters, such as lattice constants and bulk modulus, agree well with the available data. Among the P6{sub 3}/mm, P3-bar c1, and P6{sub 3}cm structures, the P6{sub 3}cm structure is found to be the most stable structure for lanthanide trihydride via the comparison of the calculated total energies. With the help of Birch-Murnaghan equation of state, the structural transitions from hexagonal to cubic for REH{sub 3} (RE=Sm, Gd, Ho, Er, and Lu) under pressure are affirmed; especially, the similar behavior of REH{sub 3} (RE= Tb, Dy, and Tm) is reasonably predicted for the first time by this means. For the transitions, the repulsive interactions of H-H atoms may play an important role in terms of the analysis of the structures in the vicinity of the theoretical phase transition.

  9. Magnetic assembly of nonmagnetic particles into photonic crystal structures.

    Science.gov (United States)

    He, Le; Hu, Yongxing; Kim, Hyoki; Ge, Jianping; Kwon, Sunghoon; Yin, Yadong

    2010-11-10

    We report the rapid formation of photonic crystal structures by assembly of uniform nonmagnetic colloidal particles in ferrofluids using external magnetic fields. Magnetic manipulation of nonmagnetic particles with size down to a few hundred nanometers, suitable building blocks for producing photonic crystals with band gaps located in the visible regime, has been difficult due to their weak magnetic dipole moment. Increasing the dipole moment of magnetic holes has been limited by the instability of ferrofluids toward aggregation at high concentration or under strong magnetic field. By taking advantage of the superior stability of highly surface-charged magnetite nanocrystal-based ferrofluids, in this paper we have been able to successfully assemble 185 nm nonmagnetic polymer beads into photonic crystal structures, from 1D chains to 3D assemblies as determined by the interplay of magnetic dipole force and packing force. In a strong magnetic field with large field gradient, 3D photonic crystals with high reflectance (83%) in the visible range can be rapidly produced within several minutes, making this general strategy promising for fast creation of large-area photonic crystals using nonmagnetic particles as building blocks.

  10. Crystal structure and vibrational spectra of piperazinium bis(4-hydroxybenzenesulphonate) molecular-ionic crystal

    Science.gov (United States)

    Marchewka, M. K.; Pietraszko, A.

    2008-02-01

    The piperazinium bis(4-hydroxybenzenesulphonate) crystallizes from water solution at room temperature in P2 1/ c space group of monoclinic system. The crystals are built up of doubly protonated piperazinium cations and ionized 4-hydroxybenzenesulphonate anions that interact through weak hydrogen bonds of O-H⋯O and N-H⋯O type. Mutual orientation of anions is determined by non-conventional hydrogen bonds of C-H⋯π type. Room temperature powder FT IR and FT Raman measurements were carried out. The vibrational spectra are in full agreement with the structure obtained from X-ray crystallography. The big single crystals of the title salt can be grown.

  11. Orange-red emitting Gd2Zr2O7:Sm3+: Structure-property correlation, optical properties and defect spectroscopy

    Science.gov (United States)

    Gupta, Santosh K.; Reghukumar, C.; Sudarshan, K.; Ghosh, P. S.; Pathak, Nimai; Kadam, R. M.

    2018-05-01

    Local structure analysis of dopant ion, understanding host to dopant energy transfer dynamics and defects characterization in a doped material which plays an important role in the designing a highly efficient opto-electronic material. In this connection a new Sm3+ doped Gd2Zr2O7 pyrochlore material was synthesized using gel-combustion technique and was characterized systematically using X-ray diffraction (XRD), time resolved photoluminescence spectroscopy (TRPLS), positron annihilation lifetime spectroscopy (PALS) and density functional theory (DFT) based ab-initio calculation. Based on DFT site selective energetics calculation and luminescence decay measurement, it was observed that the Sm3+ was distributed at both Gd3+ and Zr4+ site with higher Sm3+ fraction at the Gd3+ site. PALS was used to probe the presence of defects in the phosphor. In this work intense orange-red emission is realized through manipulating the energy transfer from host defect emission (oxygen vacancies) to Sm3+ which allows color emission from green in undoped to orange-red in doped samples. Effect of dopant concentration and annealing temperature was probed using TRPLS and PALS. These all information is highly important for researcher looking to achieve pyrochlore based phosphor materials with high quantum yield.

  12. First-principles calculation of structural and energetic properties for A2Ti2O7 (A = Lu, Er, Y, Gd, Sm, Nd, La)

    International Nuclear Information System (INIS)

    Zhang, Z.L.; Xiao, H.Y.; Zu, Xiaotao T.; Gao, Fei; Weber, William J.

    2009-01-01

    A first-principles method has been employed to investigate the structural and energetic properties for A2Ti2O7 (A = Lu, Er, Y, Gd, Sm, Nd, La), including the formation energies of the cation antisite-pair, the anion Frenkel pair that defines anion-disorder, and the coupled cation antisite-pair/anion-Frenkel. It is proposed that the interaction may have more significant influence on the radiation resistance behavior of titanate pyrochlores, although the interactions are relatively much stronger than the interactions. It is found that the defect formation energies are not simple functions of the A-site cation radii. The formation energy of the cation antisite-pair increases continuously as the A-site cation varies from Lu to Gd, and then decreases continuously with the variation of the A-site cation from Gd to La, in excellent agreement with the radiation-resistance trend of the titanate pyrochlores. The band gaps in these pyrochlores were also measured, and the band gap widths changed continuously with cation radius.

  13. Structural science using single crystal and pulse neutron scattering

    International Nuclear Information System (INIS)

    Noda, Yukio; Kimura, Hiroyuki; Watanabe, Masashi; Ishikawa, Yoshihisa; Tamura, Itaru; Arai, Masatoshi; Takahashi, Miwako; Ohshima, Ken-ichi; Abe, Hiroshi; Kamiyama, Takashi

    2008-01-01

    The application to single crystal neutron structural analysis is overviewed. Special attention is paid to the pulse neutron method, which will be available soon under J-PARC project in Japan. New proposal and preliminary experiment using Sirius at KENS are described. (author)

  14. Crystal structure, characterization and magnetic properties of a 1D ...

    Indian Academy of Sciences (India)

    Crystal structure, characterization and magnetic properties of a 1D copper(II) polymer incorporating a Schiff base with carboxylate side arm. SHYAMAPADA SHIT MADHUSUDAN NANDY CORRADO RIZZOLI CÉDRIC DESPLANCHES SAMIRAN MITRA. Regular Article Volume 128 Issue 6 June 2016 pp 913-920 ...

  15. BiFeO3 Crystal Structure at Low Temperatures

    International Nuclear Information System (INIS)

    Palewicz, A.; Sosnowska, I.; Przenioslo, R.; Hewat, A.W.

    2010-01-01

    The crystal and magnetic structure of BiFeO 3 have been studied with the use of high resolution neutron diffraction between 5 K and 300 K. The atomic coordinates in BiFeO 3 are almost unchanged between 5 K and 300 K. (authors)

  16. Effect of domains configuration on crystal structure in ferroelectric ...

    Indian Academy of Sciences (India)

    2017-09-09

    Sep 9, 2017 ... It is well known that domains and crystal structure control the physical properties of ferroelectrics. ... The as-prepared ceramics were crushed to fine pow- ders. ..... [1] Gao J, Xue D, Wang Y, Wang D, Zhang L, Wu H et al 2011.

  17. Magnetic structure of URhSi single crystal

    Czech Academy of Sciences Publication Activity Database

    Prokeš, K.; Andreev, Alexander V.; Honda, F.; Sechovský, V.

    2003-01-01

    Roč. 261, - (2003), s. 131-138 ISSN 0304-8853 R&D Projects: GA ČR GA202/02/0739 Institutional research plan: CEZ:AV0Z1010914 Keywords : URhSi single crystal * magnetization * neutron diffraction * magnetic structure determination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.910, year: 2003

  18. Fine structure of fields in 2D photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Volkov, V. S.; Bozhevolnyi, S. I.

    2006-01-01

    We resolve fine structure of fields in a single-row missing photonic crystal waveguide by finite-difference time-domain modelling and SNOM measurements. Both linear dispersion and slow-light regimes in proximity of the cutoff are addressed in the analysis....

  19. Unusual Features of Crystal Structures of Some Simple Copper Compounds

    Science.gov (United States)

    Douglas, Bodie

    2009-01-01

    Some simple copper compounds have unusual crystal structures. Cu[subscript 3]N is cubic with N atoms at centers of octahedra formed by 6 Cu atoms. Cu[subscript 2]O (cuprite) is also cubic; O atoms are in tetrahedra formed by 4 Cu atoms. These tetrahedra are linked by sharing vertices forming two independent networks without linkages between them.…

  20. Isomorph invariance of the structure and dynamics of classical crystals

    DEFF Research Database (Denmark)

    Albrechtsen, Dan; Olsen, Andreas Elmerdahl; Pedersen, Ulf Rørbæk

    2014-01-01

    This paper shows by computer simulations that some crystalline systems have curves in their thermodynamic phase diagrams, so-called isomorphs, along which structure and dynamics in reduced units are invariant to a good approximation. The crystals are studied in a classical-mechanical framework...

  1. short communication synthesis and crystal structure of a polymeric

    African Journals Online (AJOL)

    Preferred Customer

    A new polymeric zinc(II) complex, [ZnL2(PDA)]n, has been prepared by the reaction of zinc sulfate ... complex has been characterized by single-crystal X-ray diffraction. .... Molecular structure of the complex at 30% probability displacement.

  2. Characterization and crystal structures of new Schiff base macrocyclic compounds

    Czech Academy of Sciences Publication Activity Database

    Khalaji, A.D.; Ghoran, S.H.; Pojarová, Michaela; Dušek, Michal

    2015-01-01

    Roč. 56, č. 7 (2015), s. 1410-1414 ISSN 0022-4766 R&D Projects: GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : synthesis * macrocyclic Schiff base * single crystal structure analysis * spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.536, year: 2015

  3. Synthesis and structural characterization of CsNiP crystal

    Indian Academy of Sciences (India)

    Unknown

    The crystals obtained by this method were of good quality exhibiting ... type framework structure having Cs atoms inside it (figures. 3 and 4). This helps for .... Gopalakrishna G S, Prasad J S and Lokanath N K 2001 Proc. joint 4th and 6th ICSTR ...

  4. Variational cellular model of the molecular and crystal electronic structure

    International Nuclear Information System (INIS)

    Ferreira, L.G.; Leite, J.R.

    1977-12-01

    A variational version of the cellular method is developed to calculate the electronic structure of molecules and crystals. Due to the simplicity of the secular equation, the method is easy to be implemented. Preliminary calculations on the hydrogen molecular ion suggest that it is also accurate and of fast convergence [pt

  5. X-ray diffraction studies on K3Gd5 (PO4) 6 between 20K to 1073 K

    International Nuclear Information System (INIS)

    Bevara, Samatha; Achary, S.N.; Tyagi, A.K.; Sinha, A.K.; Sastry, P.U.

    2016-01-01

    Complex inorganic phosphates have been of interest due to their diversified crystal chemistry depending on composition, preparation condition as well as external parameters like temperature and pressure. In addition varieties of complex phosphates have been considered as potential host matrices for immobilization of radioactive elements as well as for selective separation of ions from high level nuclear waste or heavy metal ion pollutants from environment. Temperature and/or pressure induced structural variations are often noticed in such type complex phosphates. In K 2 O-Gd 2 O 3 -P 2 O 5 , a novel complex phosphate with K 3 Gd 5 (PO 4 ) 6 has been reported recently. In order to study the effect of temperature on crystal structure of K 3 Gd 5 (PO 4 ) 6 variable temperature XRD studies between 20 K to 1073 K were carried out and the results are presented herein

  6. A unified picture of the crystal structures of metals

    Science.gov (United States)

    Söderlind, Per; Eriksson, Olle; Johansson, Börje; Wills, J. M.; Boring, A. M.

    1995-04-01

    THE crystal structures of the light actinides have intrigued physicists and chemists for several decades1. Simple metals and transition metals have close-packed, high-symmetry structures, such as body-centred cubic, face-centred cubic and hexagonal close packing. In contrast, the structures of the light actinides are very loosely packed and of low symmetry-tetragonal, orthorhombic and monoclinic. To understand these differences, we have performed total-energy calculations, as a function of volume, for both high-and low-symmetry structures of a simple metal (aluminium), a non-magnetic transition metal (niobium), a ferromagnetic transition metal (iron) and a light actinide (uranium). We find that the crystal structure of all of these metals is determined by the balance between electrostatic (Madelung) interactions, which favour high symmetry, and a Peierls distortion of the crystal lattice, which favours low symmetry. We show that simple metals and transition metals can adopt low-symmetry structures on expansion of the lattice; and we predict that, conversely, the light actinides will undergo transitions to structures of higher symmetry on compression.

  7. A unified picture of the crystal structures of metals

    International Nuclear Information System (INIS)

    Soederlind, P.; Eriksson, O.; Johansson, B.; Wills, J.M.; Boring, A.M.

    1995-01-01

    The crystal structures of the light actinides have intrigued physicists and chemists for several decades. Simple metals and transition metals have close-packed, high-symmetry structures, such as body-centred cubic, face-centred cubic hexagonal close packing. In contrast, the structures of the light actinides are very loosely packed and of low symmetry -tetragonal, orthorhombic and monoclinic. To understand these differences, we have have performed total-energy calculations, as a function of volume, for both high- and low-symmetry structures of a simple metal (aluminium), a non-magnetic transition metal (niobium), a ferromagnetic transition metal (iron) and a light actinide (uranium). We find that the crystal structure of all these metals is determined by the balance between electrostatic (Madelung) interactions, which favour high symmetry, and a Peierls distortion of the crystal lattice, which favours low symmetry. We show that simple metals and transition metals can adopt low-symmetry structures on expansion of the lattice; and we predict that, conversely, the light actinides will undergo transitions to structures of higher symmetry on compression. (author)

  8. Coefficient of crystal lattice matching as a parameter of substrate - crystal structure compatibility in silumins

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2009-07-01

    Full Text Available Adding high-melting point elements (Mo, Nb, Ni, Ti, W to complex silumins results in hardening of the latter ones, owing to the formation of new intermetallic phases of the AlxMey type, with refinement of dendrites in α solution and crystals in β phase. The hardening is also due to the effect of various inoculants. An addition of the inoculant is expected to form substrates, the crystal lattice of which, or some (privileged lattice planes and interatomic spaces should bear a strong resemblance to the crystal nucleus. To verify this statement, using binary phase equilibria systems, the coefficient of crystal lattice matching, being one of the measures of the crystallographic similarity, was calculated. A compatibility of this parameter (up to 20% may decide about the structure compatibility between the substrate and crystal which, in turn, is responsible for the effectiveness of alloy modification. Investigations have proved that, given the temperature range of their formation, the density, the lattice type, and the lattice parameter, some intermetallic phases of the AlxMey type can act as substrates for the crystallisation of aluminium and silicon, and some of the silumin hardening phases.

  9. Band structures in Sierpinski triangle fractal porous phononic crystals

    International Nuclear Information System (INIS)

    Wang, Kai; Liu, Ying; Liang, Tianshu

    2016-01-01

    In this paper, the band structures in Sierpinski triangle fractal porous phononic crystals (FPPCs) are studied with the aim to clarify the effect of fractal hierarchy on the band structures. Firstly, one kind of FPPCs based on Sierpinski triangle routine is proposed. Then the influence of the porosity on the elastic wave dispersion in Sierpinski triangle FPPCs is investigated. The sensitivity of the band structures to the fractal hierarchy is discussed in detail. The results show that the increase of the hierarchy increases the sensitivity of ABG (Absolute band gap) central frequency to the porosity. But further increase of the fractal hierarchy weakens this sensitivity. On the same hierarchy, wider ABGs could be opened in Sierpinski equilateral triangle FPPC; whilst, a lower ABG could be opened at lower porosity in Sierpinski right-angled isosceles FPPCs. These results will provide a meaningful guidance in tuning band structures in porous phononic crystals by fractal design.

  10. Band structures in Sierpinski triangle fractal porous phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Kai; Liu, Ying, E-mail: yliu5@bjtu.edu.cn; Liang, Tianshu

    2016-10-01

    In this paper, the band structures in Sierpinski triangle fractal porous phononic crystals (FPPCs) are studied with the aim to clarify the effect of fractal hierarchy on the band structures. Firstly, one kind of FPPCs based on Sierpinski triangle routine is proposed. Then the influence of the porosity on the elastic wave dispersion in Sierpinski triangle FPPCs is investigated. The sensitivity of the band structures to the fractal hierarchy is discussed in detail. The results show that the increase of the hierarchy increases the sensitivity of ABG (Absolute band gap) central frequency to the porosity. But further increase of the fractal hierarchy weakens this sensitivity. On the same hierarchy, wider ABGs could be opened in Sierpinski equilateral triangle FPPC; whilst, a lower ABG could be opened at lower porosity in Sierpinski right-angled isosceles FPPCs. These results will provide a meaningful guidance in tuning band structures in porous phononic crystals by fractal design.

  11. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    Directory of Open Access Journals (Sweden)

    Vasily F. Shabanov

    2013-08-01

    Full Text Available Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

  12. Continuous-wave laser at 440 nm based on frequency-doubled diode-pumped Nd:GdVO(4) crystal.

    Science.gov (United States)

    Castaing, Marc; Balembois, François; Georges, Patrick

    2008-09-01

    We present for the first time, to the best of our knowledge, a frequency-doubled Nd:GdVO(4) laser operating in a cw on the pure three-level laser line at 880 nm. We obtained 300 mW at 440 nm for 23 W of incident pump power at 808 nm. Moreover, with a 25% output coupler we obtained a cw power of 1.9 W at the fundamental wavelength at 880 nm.

  13. Protein crystal structure analysis using synchrotron radiation at atomic resolution

    International Nuclear Information System (INIS)

    Nonaka, Takamasa

    1999-01-01

    We can now obtain a detailed picture of protein, allowing the identification of individual atoms, by interpreting the diffraction of X-rays from a protein crystal at atomic resolution, 1.2 A or better. As of this writing, about 45 unique protein structures beyond 1.2 A resolution have been deposited in the Protein Data Bank. This review provides a simplified overview of how protein crystallographers use such diffraction data to solve, refine, and validate protein structures. (author)

  14. Crystal structure of new AsS2 compound

    International Nuclear Information System (INIS)

    Bolotina, N. B.; Brazhkin, V. V.; Dyuzheva, T. I.; Lityagina, L. M.; Kulikova, L. F.; Nikolaev, N. A.; Verin, I. A.

    2013-01-01

    AsS 2 single crystals have been obtained for the first time from an As 2 S 3 melt at pressures above 6 GPa and temperatures above 800 K in the As 2 S 3 → AsS + AsS 2 reaction. The monoclinic structure of the new high-pressure phase is solved by X-ray diffraction analysis and compared to the structure of high-pressure AsS phase, which was studied previously.

  15. Spatially periodic structures, under femtosecond pulsed excitation of crystals

    International Nuclear Information System (INIS)

    Martynovitch, Evgueni F.; Petite, Guillaume; Dresvianski, Vladimir P.; Starchenko, Anton A.

    2004-01-01

    Measuring the luminescence intensity of specially prepared irradiation defects induced in crystals, we observe that the longitudinal structure of quasi-interferences induced by two orthogonally polarized femtosecond pulses propagating together with different velocities is insensitive to the spatial broadening due to velocity dispersion in the crystals. On the contrary, it does depend on the pulse duration when it is changed by varying the spectral width of the radiation. It thus allows a direct measurement of the coherence time of such pulses. Stability of the axial selectivity is a good sign, taking away a number of serious limitations concerning possible applications

  16. Crystal structure representations for machine learning models of formation energies

    Energy Technology Data Exchange (ETDEWEB)

    Faber, Felix [Department of Chemistry, Institute of Physical Chemistry and National Center for Computational Design and Discovery of Novel Materials, University of Basel Switzerland; Lindmaa, Alexander [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping Sweden; von Lilienfeld, O. Anatole [Department of Chemistry, Institute of Physical Chemistry and National Center for Computational Design and Discovery of Novel Materials, University of Basel Switzerland; Argonne Leadership Computing Facility, Argonne National Laboratory, 9700 S. Cass Avenue Lemont Illinois 60439; Armiento, Rickard [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping Sweden

    2015-04-20

    We introduce and evaluate a set of feature vector representations of crystal structures for machine learning (ML) models of formation energies of solids. ML models of atomization energies of organic molecules have been successful using a Coulomb matrix representation of the molecule. We consider three ways to generalize such representations to periodic systems: (i) a matrix where each element is related to the Ewald sum of the electrostatic interaction between two different atoms in the unit cell repeated over the lattice; (ii) an extended Coulomb-like matrix that takes into account a number of neighboring unit cells; and (iii) an ansatz that mimics the periodicity and the basic features of the elements in the Ewald sum matrix using a sine function of the crystal coordinates of the atoms. The representations are compared for a Laplacian kernel with Manhattan norm, trained to reproduce formation energies using a dataset of 3938 crystal structures obtained from the Materials Project. For training sets consisting of 3000 crystals, the generalization error in predicting formation energies of new structures corresponds to (i) 0.49, (ii) 0.64, and (iii) 0.37eV/atom for the respective representations.

  17. Crystal structure and magnetism of UOsAl

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A.V., E-mail: andreev@fzu.cz [Institute of Physics, Academy of Sciences, Na Slovance 2, 182 21 Prague (Czech Republic); Daniš, S. [Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, 121 16 Prague (Czech Republic); Šebek, J.; Henriques, M.S.; Vejpravová, J. [Institute of Physics, Academy of Sciences, Na Slovance 2, 182 21 Prague (Czech Republic); Gorbunov, D.I. [Institute of Physics, Academy of Sciences, Na Slovance 2, 182 21 Prague (Czech Republic); Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum, Dresden-Rossendorf, D-01314 Dresden (Germany); Havela, L. [Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, 121 16 Prague (Czech Republic)

    2017-04-15

    Crystal structure, magnetization, and specific heat were studied on single crystal of uranium intermetallic compound UOsAl. It is a hexagonal Laves phase of MgZn{sub 2} type, space group P6{sub 3}/mmc, with lattice parameters a=536.4 pm, c=845.3 pm. Shortest inter-uranium distance 313 pm (along the c-axis) is considerably smaller than the Hill limit (340 pm). The compound is a weakly temperature-dependent paramagnet with magnetic susceptibility of ≈1.5*10{sup −8} m{sup 3} mol{sup −1} (at T=2 K), which is slightly higher with magnetic field along the a-axis compared to the c-axis. The Sommerfeld coefficient of electronic specific heat has moderate value of γ=36 mJ mol{sup −1} K{sup −2}. - Highlights: • Crystal structure and magnetic properties were studied on single crystal of UOsAl with hexagonal structure of MgZn{sub 2} type. • Shortest inter-uranium distance 313 pm (along the c-axis) is considerably smaller than the Hill limit (340 pm). • UOsAl has paramagnetic ground state as the compounds with T=Fe and Ru, i.e. 3d and 4d analogues of Os.

  18. Icosahedral symmetry described by an incommensurately modulated crystal structure model

    DEFF Research Database (Denmark)

    Wolny, Janusz; Lebech, Bente

    1986-01-01

    A crystal structure model of an incommensurately modulated structure is presented. Although six different reciprocal vectors are used to describe the model, all calculations are done in three dimensions making calculation of the real-space structure trivial. Using this model, it is shown that both...... the positions of the bragg reflections and information about the relative intensities of these reflections are in full accordance with the diffraction patterns reported for microcrystals of the rapidly quenched Al86Mn14 alloy. It is also shown that at least the local structure possesses full icosahedral...

  19. Twinning structures in near-stoichiometric lithium niobate single crystals

    International Nuclear Information System (INIS)

    Yao, Shuhua; Chen, Yanfeng

    2010-01-01

    A near-stoichiometric lithium niobate single crystal has been grown by the Czochralski method in a hanging double crucible with a continuous powder supply system. Twins were found at one of the three characteristic growth ridges of the as-grown crystal. The twin structure was observed and analyzed by transmission synchrotron topography. The image shifts ΔX and ΔY in the transmission synchrotron topograph were calculated for the 3 anti 2 anti 12 and 0 anti 222 reflections based on results from high-resolution X-ray diffractometry. It is confirmed that one of the {01 anti 1 anti 2} m planes is the composition face of the twin and matrix crystals. The formation mechanism of these twins is discussed. (orig.)

  20. Crystal structure of N-(quinolin-6-ylhydroxylamine

    Directory of Open Access Journals (Sweden)

    Anuruddha Rajapakse

    2014-11-01

    Full Text Available The title compound, C9H8N2O, crystallized with four independent molecules in the asymmetric unit. The four molecules are linked via one O—H...N and two N—H...N hydrogen bonds, forming a tetramer-like unit. In the crystal, molecules are further linked by O—H...N and N—H...O hydrogen bonds forming layers parallel to (001. These layers are linked via C—H...O hydrogen bonds and a number of weak C—H...π interactions, forming a three-dimensional structure. The crystal was refined as a non-merohedral twin with a minor twin component of 0.319.

  1. Production, purification, crystallization and structure determination of H-1 Parvovirus

    International Nuclear Information System (INIS)

    Halder, Sujata; Nam, Hyun-Joo; Govindasamy, Lakshmanan; Vogel, Michèle; Dinsart, Christiane; Salomé, Nathalie; McKenna, Robert; Agbandje-McKenna, Mavis

    2012-01-01

    The production, purification, crystallization and crystallographic analysis of H-1 Parvovirus, a gene-therapy vector, are reported. Crystals of H-1 Parvovirus (H-1PV), an antitumor gene-delivery vector, were obtained for DNA-containing capsids and diffracted X-rays to 2.7 Å resolution using synchrotron radiation. The crystals belonged to the monoclinic space group P2 1 , with unit-cell parameters a = 255.4, b = 350.4, c = 271.6 Å, β = 90.34°. The unit cell contained two capsids, with one capsid per crystallographic asymmetric unit. The H-1PV structure has been determined by molecular replacement and is currently being refined

  2. Band structure and optical properties of diglycine nitrate crystal

    International Nuclear Information System (INIS)

    Andriyevsky, Bohdan; Ciepluch-Trojanek, Wioleta; Romanyuk, Mykola; Patryn, Aleksy; Jaskolski, Marcin

    2005-01-01

    Experimental and theoretical investigations of the electron energy characteristics and optical spectra for diglycine nitrate crystal (DGN) (NH 2 CH 2 COOH) 2 .HNO 3 , in the paraelectric phase (T=295K) are presented. Spectral dispersion of light reflection R(E) have been measured in the range of 3-22eV and the optical functions n(E) and k(E) have been calculated using Kramers-Kronig relations. First principal calculations of the electron energy characteristic and optical spectra of DGN crystal have been performed in the frame of density functional theory using CASTEP code (CAmbridge Serial Total Energy Package). Optical transitions forming the low-energy edge of fundamental absorption are associated with the nitrate groups NO 3 . Peculiarities of the band structure and DOS projected onto glycine and NO 3 groups confirm the molecular character of DGN crystal

  3. Synthesis and characterization of physical properties of Gd{sub 2}O{sub 2}S:Pr{sup 3+} semi-nanoflower phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Bagheri, A.; Rezaee Ebrahim Saraee, Kh.; Shakur, H.R. [University of Isfahan, Department of Nuclear Engineering, Faculty of Advance Sciences and Technologies, Isfahan (Iran, Islamic Republic of); Zamani Zeinali, H. [Nuclear Science and Technology Research Institute, Agriculture, Medical and Industrial Research School, Karaj (Iran, Islamic Republic of)

    2016-05-15

    Pure gadolinium oxysulfide phosphor (Gd{sub 2}O{sub 2}S) and trivalent praseodymium-doped gadolinium oxysulfide phosphor (Gd{sub 2}O{sub 2}S:Pr{sup 3+}) scintillators with semi-nanoflower crystalline structures were successfully synthesized through a precipitation method and subsequent calcination treatment as a converter for X-ray imaging detectors. The characterization such as the crystal structures and nanostructure of Gd{sub 2}O{sub 2}S:Pr{sup 3+} scintillator measured by XRD and FeE-SEM experiment. The optical properties of Gd{sub 2}O{sub 2}S:Pr{sup 3+} scintillator were studied. Luminescence spectra of Gd{sub 2}O{sub 2}S:Pr{sup 3+} under 320 nm UV excitation show a green emission at near 511 nm corresponding to the {sup 3}P{sub 0}-{sup 3}H{sub 4} of Pr ions. After scintillation properties of synthesized Gd{sub 2}O{sub 2}S:Pr{sup 3+} scintillator investigated, Gd{sub 2}O{sub 2}S:Pr{sup 3+} scintillating film fabricated on a glass substrate by a sedimentation method. X-ray imaging of the fabricated scintillators confirmed that the Gd{sub 2}O{sub 2}S:Pr{sup 3+} scintillator could be used for radiography applications in which good spatial resolution is needed. (orig.)

  4. First principles investigation of the structure of a bacteriochlorophyll crystal

    Energy Technology Data Exchange (ETDEWEB)

    Marchi, M. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)]|[Centre d`Etudes Saclay, Gif-sur-Yvette (France); Hutter, J.; Parrinello, M. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    1996-08-21

    In this communication we present an ab initio study of the crystal of methyl bacteriophorbide (MeBPheo) a, a bacteriochlorophyll derivative, and high-precision structure of which is available. Our main purpose has been to investigate the viability of the technique toward complex molecular systems relevant to biologically important phenomena, in this particular case photosynthesis. Here we present the following results: First, we show that DFT is capable of calculating nuclear positions in excellent agreement with the experimental X-ray structure. Second, the calculated electronic density of the HOMO orbital reveals a {pi} type bond between rings I and III, consistent with the one-dimensional chain structure of the MeBPheo a molecules in the crystal. Finally, after performing the optimization of the molecular geometry with one electron in the LUMO state, we find localized bond length changes near the ring II of the MeBPheo a. 19 refs., 3 figs.

  5. High-brightness tapered laser diodes with photonic crystal structures

    Science.gov (United States)

    Li, Yi; Du, Weichuan; Kun, Zhou; Gao, Songxin; Ma, Yi; Tang, Chun

    2018-02-01

    Beam quality of tapered laser diodes is limited by higher order lateral mode. On purpose of optimizing the brightness of tapered laser diodes, we developed a novel design of tapered diodes. This devices based on InGaAs/AlGaAs asymmetry epitaxial structure, containing higher order lateral mode filtering schemes especially photonic crystal structures, which fabricated cost effectively by using standard photolithography and dry etch processes. Meanwhile, the effects of photonic crystal structures on mode control are also investigated theoretically by FDBPM (Finite-Difference Beam Propagation Method) calculation. We achieved a CW optical output power of 6.9W at 940nm for a single emitter with 4 mm cavity length. A nearly diffraction limited beam of M2 ≍1.9 @ 0.5W has been demonstrated, and a highest brightness of β =75MW/(cm2 ·sr) was reached.

  6. Crystal structure and thermal behavior of KB3O6

    International Nuclear Information System (INIS)

    Bubnova, R.S.; Fundamenskij, V.S.; Filatov, S.K.; Polyakova, I.G.

    2004-01-01

    The structure of potassium triborate prepared in metastable state by crystallization from melt at ∼ 800 deg C was studied by the method of X-ray diffraction analysis. It was ascertained that KB 3 O 6 belongs to monoclinic crystal system, space group P2 1 /c, a = 9.319(1), b = 6.648(1), c = 21.094(2) A, β = 94.38(1) deg, Z = 12. The compound is referred to a new structural type. Anion of the structure is a single boron-oxygen frame formed by three independent rigid triborate rings of [B 3 O 5 ] - , each of them consisting of two BO 3 triangles and BO 4 tetrahedron. Phase transformations during KB 3 O 6 heating up to 800 deg C, as well as thermal expansion in the range of 20-650 deg C, were studied [ru

  7. The crystal structure and the phase transitions of pyridinium trifluoromethanesulfonate

    International Nuclear Information System (INIS)

    Jesariew, Dominik; Ilczyszyn, Maria M; Pietraszko, Adam

    2014-01-01

    The calorimetric and optical studies and the structural properties of pyridinium trifluoromethanesulfonate (abbreviated as PyHOTf) are reported. A sequence of four fully reversible solid–solid phase transitions, at 223.0, 309.0, 359.9 and 394.3 K, has been discovered. The phase transition sequence was confirmed by x-ray diffraction data. The crystal structures of three phases (V, IV and III) have been determined from the single crystal x-ray diffraction data. Structural properties of the high temperature phases are characterized using powder x-ray diffraction data measured in the 290–425 K temperature range. The structural changes triggered by the temperature change are discussed in relation to the phase transitions. Two low temperature phases (V and IV) belong to the P4 3 2 1 2 space group of the tetragonal system. The intermediate phases (III and II) are monoclinic and the prototype high temperature phase (I) is a pseudo-cubic (tetragonal) one. The low temperature phases (V and IV) are well ordered. The crystal structure of intermediate (III and II) and prototype (I) phases are characterized by high disorder of the pyridinium cations and triflate anions. (papers)

  8. Molecular Complex of Lumiflavin and 2-Aminobenzoic Acid : Crystal Structure, Crystal Spectra, and Solution Properties

    OpenAIRE

    Shieh, Huey-Sheng; Ghisla, Sandro; Hanson, Louise Karle; Ludwig, Martha L.; Nordman, Christer E.

    1981-01-01

    The molecular complex lumiflavin-2-aminobenzoic acid monohydrate (C13H12N402●C7H7N02●H2O)crystallizes from aqueous solution as red triclinic prisms. The space group is P1 with cell dimensions a = 9.660 A, b = 14.866 Å, c = 7.045 Å, α = 95.44°, β = 95.86°, and γ = 105.66°. The crystal structure was solved by direct methods and refined by block-diagonal least-squares procedures to an R value of 0.050 on the basis of 1338 observed reflections. The structure is composed of stacks of alternating l...

  9. Organic compounds containing methoxy and cyanoacrylic acid: Synthesis, characterization, crystal structures, and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Khalaji, A. D., E-mail: alidkhalaji@yahoo.com [Golestan University, Department of Chemistry, Faculty of Science (Iran, Islamic Republic of); Maddahi, E. [Iran University of Science & Technology, Ms.C Educated, Department of Chemistry (Iran, Islamic Republic of); Dusek, M.; Fejfarova, K. [Institute of Physics of the ASCR, v.v.i. (Czech Republic); Chow, T. J. [Academia Sinica, Institute of Chemistry (China)

    2015-12-15

    Metal-free organic compounds 24-SC ((E)-2-cyano-3-(2,4-dimethoxyphenyl)acrylic acid) and 34-SC ((E)-2-cyano-3-(3,4-dimethoxyphenyl)acrylic acid), containing methoxy groups as a donor and the acrylic acid as an acceptor were synthesized and characterized by CHN, FT-IR, UV-Vis, {sup 1}H-NMR and single crystal X-ray diffraction and used as photosensitizers for the application of dye-sensitized solar cells (DSSC). The sensitizing characteristics of them were evaluated. Both compounds contain the natural molecule, its anionic form and the piperidinium cation and they differ by number of these molecules in the asymmetric unit. To get further insight into the effect of molecular structure on the performance of DSSC, their geometry and energies of HOMO and LUMO were optimized by density functional theory calculation at the B3LYP/6-31G(d) level with Gaussian 03. Overall conversion efficiencies of 0.78 under full sunlight irradiation are obtained for DSSCs based on the new metal-free organic dyes 24-SC and 34-SC.

  10. Study of the Polarization Behavior of Ce0.9Gd0.1O2-δ Single Crystals below 350°C to Room Temperature

    DEFF Research Database (Denmark)

    Neuhaus, K.; Bernemann, M.; Hansen, Karin Vels

    2016-01-01

    was investigated by mapping the introduced defect gradient and its decay with time using Kelvin probe force microscopy. The generated surface potential gradients were found to have a diameter of up to 1 μm, which is explained by the local ionization of defect associates by the applied high electric field......Single crystalline ceria samples with the composition Ce0.9Gd0.1O2-δ were pre-polarized with ±5 V for up to 300 s using a Pt coated AFM tip as working electrode. The direct contact zone had a diameter of potential of the samples....... Measurements were performed at room temperature and 50°C. The polarization behavior of the Ce0.9Gd0.1O2-δ single crystals was compared to cyclovoltammetry and polarization-relaxation experiments at T ≤ 350°C and in dry air or nitrogen which were performed using a specially suited AFM (Controlled Atmosphere...

  11. Preparation of high magneto-optical performance and crystalline quality Ce{sub 1}Gd{sub 2}Fe{sub 5−x}Ga{sub x}O{sub 12} films on CLNGG substrate crystal

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Qiu-ping; Zheng, Ze-yuan; Lin, Nan-xi; Liu, Xiao-feng; Hong, Can-huang; Hu, Xiao-lin, E-mail: linamethyst@fzu.edu.cn; Zhuang, Nai-feng; Chen, Jian-zhong, E-mail: j.z.chen@fzu.edu.cn

    2016-11-01

    Thin films of Ce{sub 1}Gd{sub 2}Fe{sub 5−x}Ga{sub x}O{sub 12} (Ce,Ga:GIG) were prepared on Gd{sub 3}Ga{sub 5}O{sub 12} (GGG) and Ca{sub 2.90}Li{sub 0.30}Nb{sub 1.93}Ga{sub 2.76}O{sub 12} (CLNGG) substrates by using radio frequency magnetron sputtering technique. The phase, grain orientation, surface morphology, transmittance, magnetism and magnetic circular dichroism (MCD) properties of films were analyzed. And the effects of lattice mismatch and non-magnetic Ga{sup 3+}-doping were discussed. The results show that the films with higher crystallized quality and lower stress can be obtained by growing on CLNGG than on GGG. Moreover, the coercive force, magnetization, magneto-optical effect intensity and orientation of film can be effectively regulated by adjusting Ga{sup 3+}-doped concentration. - Highlights: • With excellent magneto-optical performance, Ce,Ga:GIG film has a good application prospect. • Ce,Ga:GIG film with high quality were prepared on CLNGG by RF magnetron sputtering. • Crystalline quality and morphology of films are intently related to the substrate. • Ga{sup 3+} doping obviously affect on magnetism and magneto-optical property of Ce:GIG film.

  12. Detailed crystallization study of co-precipitated Y{sub 1.47} Gd{sub 1.53} Fe{sub 5} O{sub 12} and relevant magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Serra, Rogerio Arving [Instituto de Criminalistica Carlos Eboli (ICCE), Rio de Janeiro, RJ (Brazil); Ogasawara, Tsuneharu; Ogasawara, Angelica Soares [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE). Dept. de Engenharia Metalurgica e de Materiais]. E-mail: ogasawat@metalmat.ufrj.br

    2007-07-01

    The crystallization process of co-precipitated Y{sub 1.5}Gd{sub 1.5}Fe{sub 5}O{sub 12} powder heated up to 1000 deg C at rate of 5 deg C min{sup -1} was investigated. Above 810 deg C crystalline Y{sub 1.47}Gd{sub 1.53}Fe{sub 5}O{sub 12} was obtained with a lattice parameter of 12.41 A and a theoretical density of 5.84 g cm{sup -3}. Dry pressed rings were sintered at 1270 and 1320 deg C, increasing the grain-size from 3.1 to 6.5 {mu}m, the theoretical density by 87.6 to 95.3% and decreasing H{sub c} from 2.9725 to 1.4005 Oe. Additionally, Hc increased when the frequency of the hysteresis graph varied from 60 Hz to 10 kHz, the curie temperature was 282.4 deg C and Ms equalled 9.25 emu g{sup -1} (0.17 kG) agreeing well with the B{sub s}-value of the hysteresis graph and literature values. (author)

  13. One dimensional coordination polymers: Synthesis, crystal structures and spectroscopic properties

    Science.gov (United States)

    Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Şenyel, Mustafa; Şahin, Onur

    2016-11-01

    Two new one dimensional (1D) cyanide complexes, namely [M(4-aepy)2(H2O)2][Pt(CN)4], (4-aepy = 4-(2-aminoethyl)pyridine M = Cu(II) (1) or Zn(II) (2)), have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. The crystallographic analyses reveal that 1 and 2 are isomorphous and isostructural, and crystallize in the monoclinic system and C2 space group. The Pt(II) ions are coordinated by four cyanide-carbon atoms in the square-planar geometry and the [Pt(CN)4]2- ions act as a counter ion. The M(II) ions display an N4O2 coordination sphere with a distorted octahedral geometry, the nitrogen donors belonging to four molecules of the organic 4-aepy that act as unidentate ligands and two oxygen atoms from aqua ligands. The crystal structures of 1 and 2 are similar each other and linked via intermolecular hydrogen bonding, Pt⋯π interactions to form 3D supramolecular network. Vibration assignments of all the observed bands are given and the spectral features also supported to the crystal structures of the complexes.

  14. Synthesis and characterization of electrolyte-grade 10%Gd-doped ceria thin film/ceramic substrate structures for solid oxide fuel cells

    DEFF Research Database (Denmark)

    Chourashiya, M. G.; Bharadwaj, S. R.; Jadhav, L. D.

    2010-01-01

    In the present research, spray pyrolysis technique is employed to synthesize 10%Gd-doped ceria (GDC) thin films on ceramic substrates with an intention to use the "film/substrate" structure in solid oxide fuel cells. GDC films deposited on GDC substrate showed enhanced crystallite formation....... In case of NiO-GDC composite substrate, the thickness of film was higher (∼ 13 μm) as compared to the film thickness on GDC substrate (∼ 2 μm). The relative density of the films deposited on both the substrates was of the order of 95%. The impedance measurements revealed that ionic conductivity of GDC...

  15. Crystal structure of human protein kinase CK2

    DEFF Research Database (Denmark)

    Niefind, K; Guerra, B; Ermakowa, I

    2001-01-01

    The crystal structure of a fully active form of human protein kinase CK2 (casein kinase 2) consisting of two C-terminally truncated catalytic and two regulatory subunits has been determined at 3.1 A resolution. In the CK2 complex the regulatory subunits form a stable dimer linking the two catalyt...... as a docking partner for various protein kinases. Furthermore it shows an inter-domain mobility in the catalytic subunit known to be functionally important in protein kinases and detected here for the first time directly within one crystal structure.......The crystal structure of a fully active form of human protein kinase CK2 (casein kinase 2) consisting of two C-terminally truncated catalytic and two regulatory subunits has been determined at 3.1 A resolution. In the CK2 complex the regulatory subunits form a stable dimer linking the two catalytic...... subunits, which make no direct contact with one another. Each catalytic subunit interacts with both regulatory chains, predominantly via an extended C-terminal tail of the regulatory subunit. The CK2 structure is consistent with its constitutive activity and with a flexible role of the regulatory subunit...

  16. Crystal structure optimisation using an auxiliary equation of state

    Science.gov (United States)

    Jackson, Adam J.; Skelton, Jonathan M.; Hendon, Christopher H.; Butler, Keith T.; Walsh, Aron

    2015-11-01

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy-volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other "beyond" density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu2ZnSnS4 and the magnetic metal-organic framework HKUST-1.

  17. Crystal structure optimisation using an auxiliary equation of state

    International Nuclear Information System (INIS)

    Jackson, Adam J.; Skelton, Jonathan M.; Hendon, Christopher H.; Butler, Keith T.; 3 Institute and Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of))" data-affiliation=" (Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Global E3 Institute and Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of))" >Walsh, Aron

    2015-01-01

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy–volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other “beyond” density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu 2 ZnSnS 4 and the magnetic metal-organic framework HKUST-1

  18. Crystal structure optimisation using an auxiliary equation of state

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, Adam J.; Skelton, Jonathan M.; Hendon, Christopher H.; Butler, Keith T. [Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Walsh, Aron, E-mail: a.walsh@bath.ac.uk [Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Global E" 3 Institute and Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2015-11-14

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy–volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other “beyond” density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu{sub 2}ZnSnS{sub 4} and the magnetic metal-organic framework HKUST-1.

  19. Generating a 2.4-W cw Green Laser by Intra-Cavity Frequency Doubling of a Diode-Pumped Nd:GdVO4 Laser with a MgO:PPLN Crystal

    International Nuclear Information System (INIS)

    Lu Jun; Liu Yan-Hua; Zhao Gang; Hu Xiao-Peng; Zhu Shi-Ning

    2012-01-01

    High-power cw green laser radiation is generated by intra-cavity frequency doubling of a diode-pumped Nd:GdVO 4 laser with a MgO-doped periodically-poled LiNbO 3 (MgO:PPLN) crystal at room temperature. An average power of 2.4 W at 0.53 μm is obtained under the pump 15 W at 808 nm, corresponding to an overall optical-to-optical conversion efficiency of 16%. The M 2 factor of the green beam is 3.90 and 1.34 for the horizontal and vertical direction, respectively. In addition, the power fluctuation is measured to be about ±5%

  20. Cooperative down-conversion of UV light in disordered scheelitelike Yb-doped NaGd(MoO4)2 and NaLa(MoO4)2 crystals

    Science.gov (United States)

    Subbotin, K. A.; Osipova, Yu. N.; Lis, D. A.; Smirnov, V. A.; Zharikov, E. V.; Shcherbakov, I. A.

    2017-07-01

    Concentration series of disordered scheelitelike Yb:NaGd(MoO4)2 and Yb:NaLa(MoO4)2 single crystals are grown by the Czochralski method. The actual concentrations of Yb3+ ions in the crystals are determined by optical-absorption spectroscopy. The luminescence of Yb3+ ions in these crystals in the region of 1 μm is studied under UV and IR excitation. In the case of UV excitation, this luminescence appears as a result of nonradiative excited state energy transfer from donor centers of unknown nature to ytterbium. The character of the concentration dependence of Yb3+ luminescence indicates that the energy transfer at high Yb concentrations occurs with active participation of a cooperative mechanism, according to which the excitation energy of one donor center is transferred simultaneously to two Yb3+ ions. In other words, the quantum yield of this transfer exceeds unity, which can be used to increase the efficiency of crystalline silicon (c-Si) solar cells.

  1. Investigation of Gd compounds using synchrotron radiation

    International Nuclear Information System (INIS)

    Tyszka, B.; Szade, J.; Burian, W.; Skorek, G.; Deniszczyk, J.; Sikora, M.; Zajac, D.; Kapusta, Cz.; Matteucci, M.; Bondino, F.; Zacchigna, M.; Zangrando, M.

    2005-01-01

    The electronic structure of ferromagnetic compound GdTiGe has been investigated using element sensitive methods-X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and resonant inelastic X-ray scattering (RIXS). Additionally, another ferromagnet GdTiSi has been studied using XMCD. XMCD revealed a strong dichroic signal at Gd L 2 and L 3 edges, which can be related to polarisation of Gd 5d band. XAS at Ti L 2,3 edges has exhibited a structure which appeared to be in general agreement with the LAPW calculations. RIXS spectra have shown some resonance features for photon energies close to Ti L 2 and Gd M 5 edges

  2. CRYSTAL AND MOLECULAR STRUCTURE OF 5-NITROPIRIDINE PIPERIDINE-SULFENAMIDE

    OpenAIRE

    Brito, Iván; León, Yasna; Arias, Mauricio; Vargas, Danitza; Carmona, Francisco; Ramírez, Eduardo; Restovic, Ambrosio; Cárdenas, Alejandro; Wittke, Oscar; López-Rodríguez, Matías

    2002-01-01

    The crystal and molecular structure of 5-nitropiridine piperidine-sulfenamide, C10H13N3O2 S is described and compared with other sulfenamides and with other similar compounds. This structure belongs to a type of divalent sulphur compound and crystallizes in the orthorhombic space group Pnma with a= 27.810(4), b=6.797(1), c=6.110(1)Å, and Dx =1.376 g cm-3 with Z=4. The S-N bond distance of 1.699(4) Å is shorter than a single S-N bond [1.74 Å]. The NO2-(C6H3N)-S-N(C 5H10) molecule lies on a cry...

  3. Parallelization for X-ray crystal structural analysis program

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Hiroshi [Japan Atomic Energy Research Inst., Tokyo (Japan); Minami, Masayuki; Yamamoto, Akiji

    1997-10-01

    In this report we study vectorization and parallelization for X-ray crystal structural analysis program. The target machine is NEC SX-4 which is a distributed/shared memory type vector parallel supercomputer. X-ray crystal structural analysis is surveyed, and a new multi-dimensional discrete Fourier transform method is proposed. The new method is designed to have a very long vector length, so that it enables to obtain the 12.0 times higher performance result that the original code. Besides the above-mentioned vectorization, the parallelization by micro-task functions on SX-4 reaches 13.7 times acceleration in the part of multi-dimensional discrete Fourier transform with 14 CPUs, and 3.0 times acceleration in the whole program. Totally 35.9 times acceleration to the original 1CPU scalar version is achieved with vectorization and parallelization on SX-4. (author)

  4. Band structure and optical properties of opal photonic crystals

    Science.gov (United States)

    Pavarini, E.; Andreani, L. C.; Soci, C.; Galli, M.; Marabelli, F.; Comoretto, D.

    2005-07-01

    A theoretical approach for the interpretation of reflectance spectra of opal photonic crystals with fcc structure and (111) surface orientation is presented. It is based on the calculation of photonic bands and density of states corresponding to a specified angle of incidence in air. The results yield a clear distinction between diffraction in the direction of light propagation by (111) family planes (leading to the formation of a stop band) and diffraction in other directions by higher-order planes (corresponding to the excitation of photonic modes in the crystal). Reflectance measurements on artificial opals made of self-assembled polystyrene spheres are analyzed according to the theoretical scheme and give evidence of diffraction by higher-order crystalline planes in the photonic structure.

  5. An arc detector for neutron crystal structure investigations

    Energy Technology Data Exchange (ETDEWEB)

    Habib, N [Reactor and Neutron Physics Dept., Nuclear Research Center. AEA, Cairo (Egypt)

    1997-12-31

    An arc detector for neutron structure investigations of powder crystals using time-of-flight technique is described. In order to enable the measurement of integral intensity from about 1/4 of the Debye-Scherrer ring and for simplicity reasons, the scattering angle 20-90 degree was chosen and a special arc collimator was built. The arc collimator-detector had a divergency of about 20 minutes of arc, and the distance between detector-sample was 64 cm. Four {sup 3} He detectors were fixed on the arc of the collimator. Both efficiency and space sensitivity of the detector were determined using a point neutron source. Results of measurements show that parameters of the arc detector are acceptable for high resolution crystal structure investigations. 6 figs.

  6. Crystal structure of N′-hydroxypyrimidine-2-carboximidamide

    Directory of Open Access Journals (Sweden)

    Nithianantham Jeeva Jasmine

    2014-10-01

    Full Text Available The title compound, C5H6N4O, is approximately planar, with an angle of 11.04 (15° between the planes of the pyrimidine ring and the non-H atoms of the carboximidamide unit. The molecule adopts an E configuration about the C=N double bond. In the crystal, adjacent molecules are linked by pairs of N—H...O hydrogen bonds, forming inversion dimers with an R22(10 ring motif. The dimers are further linked via N—H...N and O—H...N hydrogen bonds into a sheet structure parallel to the ac plane. The crystal structure also features N—H...O and weak C—H...O hydrogen bonds and offset π–π stacking interactions between adjacent pyrimidine rings [centroid–centroid distance = 3.622 (1 Å].

  7. CCDC 1515632: Experimental Crystal Structure Determination : hexakis(dimethyl sulfoxide)-manganese(ii) tetraiodide

    KAUST Repository

    Haque, M.A.; Davaasuren, Bambar; Rothenberger, Alexander; Wu, Tao

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  8. CCDC 1475929: Experimental Crystal Structure Determination : trimethylammonium tribromo-tin(iv)

    KAUST Repository

    Dang, Yangyang; Zhong, Cheng; Zhang, Guodong; Ju, Dianxing; Wang, Lei; Xia, Shengqing; Xia, Haibing; Tao, Xutang

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  9. CCDC 1475930: Experimental Crystal Structure Determination : trimethylammonium trichloro-tin(iv)

    KAUST Repository

    Dang, Yangyang; Zhong, Cheng; Zhang, Guodong; Ju, Dianxing; Wang, Lei; Xia, Shengqing; Xia, Haibing; Tao, Xutang

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  10. CCDC 1475931: Experimental Crystal Structure Determination : trimethylammonium trichloro-tin(iv)

    KAUST Repository

    Dang, Yangyang; Zhong, Cheng; Zhang, Guodong; Ju, Dianxing; Wang, Lei; Xia, Shengqing; Xia, Haibing; Tao, Xutang

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  11. CCDC 1482638: Experimental Crystal Structure Determination : trimethylammonium trichloro-tin(iv)

    KAUST Repository

    Dang, Yangyang; Zhong, Cheng; Zhang, Guodong; Ju, Dianxing; Wang, Lei; Xia, Shengqing; Xia, Haibing; Tao, Xutang

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  12. Potassium and magnesium succinatouranilates – Synthesis and crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, S.A., E-mail: serg.alex.novikov@gmail.com [Samara National Research University, 443086 Samara (Russian Federation); Grigoriev, M.S. [Frumkin Institute of Physical Chemistry and Electrochemistry RAS, 119071 Moscow (Russian Federation); Serezhkina, L.B.; Serezhkin, V.N. [Samara National Research University, 443086 Samara (Russian Federation)

    2017-04-15

    Single crystal X-ray diffraction has been applied to determine the structures of two new uranyl coordination polymers: K{sub 2}[(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}] (1) and [Mg(H{sub 2}O){sub 6}] [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]·2H{sub 2}O (2), where C{sub 4}H{sub 4}O{sub 4}{sup 2-} is succinate anion. Crystals of 1 and 2 contain polymeric complex anions [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]{sup 2-} with the same A{sub 2}Q{sup 02}{sub 3} crystallochemical formula (A=UO{sub 2}{sup 2+}, Q{sup 02}=C{sub 4}O{sub 4}H{sub 4}{sup 2-}), and have layered (1) or chain (2) structure. It has been found, that conformation of succinate ions is one of the factors, which affects the structure of [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]{sup 2-} anions. IR spectra of these new compounds are in good agreement with crystallographic data. Topological analysis of the uranium dicarboxylates with A{sub 2}Q{sup 02}{sub 3} crystallochemical formula has shown the presence of five isomers which differ from each other in coordination sequences and / or dimensionality. - Graphical abstract: Crystal structures of two new uranium(VI) coordination polymers with succinate linkers, namely K{sub 2}[(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}] (1) and [Mg(H{sub 2}O){sub 6}][(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]·2H{sub 2}O (2), were determined by single-crystal XRD. Crystals of studied compounds are based on 2D or 1D structural units with the same composition and crystallochemical formula. Topological isomerism in A{sub 2}Q{sup 02}{sub 3} crystallochemical group and conformations of succinate anions in uranyl complexes are under discussion. - Highlights: • Two new uranium coordination polymers were synthesized. • Their structural units have the same composition and crystallochemical formula. • In spite the same composition and CCF dimensionality of units is different. • Structural features of uranyl CPs

  13. Effect of BSO addition on Cu-O bond of GdBa{sub 2}Cu{sub 3}O{sub 7-x} films with varying thickness probed by extended x-ray absorption fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, H. K.; Lee, J. K.; Yang, D. S.; Kang, B. [Chungbuk National University, Cheongju (Korea, Republic of); Kang, W. N. [Dept. of Physics, Sungkyunkwan University, Suwon (Korea, Republic of)

    2016-12-15

    We investigated the relation between the Cu-O bond length and the superconducting properties of BaSnO{sub 3} (BSO)-added GdBa{sub 2}Cu{sub 3}O{sub 7-x} (GdBCO) thin films by using extended x-ray absorption fine structure (EXAFS) spectroscopy. 4 wt.% BaSnO{sub 3} (BSO) added GdBa{sub 2}Cu{sub 3}O{sub 7-x} (GdBCO) thin films with varying thickness from 0.2 μm to 1.0 μm were fabricated by using pulsed laser deposition (PLD) method. The transition temperature (T{sub c}) and the residual resistance ratio (RRR) of the GdBCO films increased with increasing thickness up to 0.8 μm, where the crystalline BSO has the highest peak intensity, and then decreased. This uncommon behaviors of T{sub c} and RRR are likely to be created by the addition of BSO, which may change the ordering of GdBCO atomic bonds. Analysis from the Cu K-edge EXAFS spectroscopy showed an interesting thickness dependence of ordering behavior of BSO-added GdBCO films. It is noticeable that the ordering of Cu-O bond and the transition temperature are found to show opposite behaviors in the thickness dependence. Based on these results, the growth of BSO seemingly have evident effect on the alteration of the local structure of GdBCO film.

  14. Crystal Structure of the Human Laminin Receptor Precursor

    Energy Technology Data Exchange (ETDEWEB)

    Jamieson,K.; Wu, J.; Hubbard, S.; Meruelo, D.

    2008-01-01

    The human laminin receptor (LamR) interacts with many ligands, including laminin, prions, Sindbis virus, and the polyphenol (-)-epigallocatechin-3-gallate (EGCG), and has been implicated in a number of diseases. LamR is overexpressed on tumor cells, and targeting LamR elicits anti-cancer effects. Here, we report the crystal structure of human LamR, which provides insights into its function and should facilitate the design of novel therapeutics targeting LamR.

  15. Incommensurate composite crystal structure of scandium-II

    International Nuclear Information System (INIS)

    Fujihisa, Hiroshi; Gotoh, Yoshito; Yamawaki, Hiroshi; Sakashita, Mami; Takeya, Satoshi; Honda, Kazumasa; Akahama, Yuichi; Kawamura, Haruki

    2005-01-01

    The long-unknown crystal structure of the high pressure phase scandium-II was solved by powder x-ray diffraction and was found to have tetragonal host channels along the c axis and guest chains that are incommensurate with the host, as well as the high pressure phases of Ba, Sr, Bi, and Sb. The pressure dependences of the lattice constants, the incommensurability, the atomic distances, and the atomic volume were investigated

  16. Band structure and optical properties of opal photonic crystals

    OpenAIRE

    Pavarini, E.; Andreani, L. C.; Soci, C.; Galli, M.; Marabelli, F.; Comoretto, D.

    2005-01-01

    A theoretical approach for the interpretation of reflectance spectra of opal photonic crystals with fcc structure and (111) surface orientation is presented. It is based on the calculation of photonic bands and density of states corresponding to a specified angle of incidence in air. The results yield a clear distinction between diffraction in the direction of light propagation by (111) family planes (leading to the formation of a stop band) and diffraction in other directions by higher-order...

  17. Crystal structures of unsymmetrically mixed β-pyrrole substituted ...

    Indian Academy of Sciences (India)

    NiTPP(Ph)3(CN)5, 3 complex was synthesized and its solvated structure was examined by crystallography. ... sive interactions among the peripheral substituents.28,29 ... 1H NMR spectra of porphyrins were. 1047 ... Single crystals of MTPP(Ph)3Cl5 (M = 2H and Ni(II)) .... by ∼0.3–0.6ppm but β-pyrrole phenyls do not show.

  18. Crystal structure of the sodium-potassium pump

    DEFF Research Database (Denmark)

    Morth, J Preben; Pedersen, Bjørn Panyella; Toustrup-Jensen, Mads S

    2007-01-01

    The Na+,K+-ATPase generates electrochemical gradients for sodium and potassium that are vital to animal cells, exchanging three sodium ions for two potassium ions across the plasma membrane during each cycle of ATP hydrolysis. Here we present the X-ray crystal structure at 3.5 A resolution......-subunit is contained within a pocket between transmembrane helices and seems to be a novel regulatory element controlling sodium affinity, possibly influenced by the membrane potential. Udgivelsesdato: 2007-Dec-13...

  19. Crystal structure studies on plate/shelf like disodium ditungstate

    Indian Academy of Sciences (India)

    Inorganic materials; disodium ditungstate; crystal structure; scanning electron microscopy; X-ray ... generation, and horizontal electric furnace with quartz tube ... Unit cell dimensions: a = 7·22192(11) Е, b = 11·91559(17) Е, c = 14·74755(23) Е. Cell content: 8 Na2W2O7). Atom. Position. X(σ(X)). Y(σ(Y)). Z(σ(Z)). B(σ(B)). W (1).

  20. Crystal structure of the uranyl-oxide mineral rameauite

    Czech Academy of Sciences Publication Activity Database

    Plášil, Jakub; Škoda, R.; Čejka, J.; Bourgoin, V.; Boulliard, J.C.

    2016-01-01

    Roč. 28, č. 5 (2016), s. 959-967 ISSN 0935-1221 R&D Projects: GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : rameauite * uranyl-oxide hydroxy-hydrate * crystal structure * Raman spectrum Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.362, year: 2016

  1. Crystalline structure of the manganites solid solution RE(Me,MnO3, (RE=Gd,Er; Me=Ni,Co

    Directory of Open Access Journals (Sweden)

    Peña, O.

    2009-08-01

    Full Text Available The structural properties of the manganites solid solution RE(Me,MnO3, RE=Er,Gd, have been studied by X-ray diffraction and electric measurements. Powders were prepared by solid state reaction between the component oxides. Incorporation of Ni2+ or Co2+ on the lattice in the Mn sites leads to changes in the parameters and symmetry of the perovskite or hexagonal compounds GdMnO3 and ErMnO3 respectively. The phase transitions depend on the amount of substituted Jahn-Teller Mn3+ cations, and, therefore, of the cooperative Jahn-Teller interaction weakness. Solid solutions based on GdMnO3 perovskite compound change from O’-type to O-type orthorhombic perovskite symmetry when the Mn3+ cation amount decreases, because of the progressive substitution for Ni, Co. This transition occurs for lower amount of Ni2+ than for Co2+ cation. The Er-based solid solutions showed a different behaviour. For Ni2+ and Co2+ incorporation there are changes from hexagonal ErMnO3-type lattice to perovskite-type symmetry, for 20 at% and 30 at% respectively of substituting cations. The resultant perovskites crystallised directly in the O-type orthorhombic perovskite structure. The steric influence seems to play a secondary role, such as it can be deduced of the small variation of the Goldschmidt tolerance factor, t, for perovskite structure.

    Las propiedades estructurales de las soluciones sólidas RE(Me,MnO3, RE=Gd,Er, Me=Ni,Co, han sido estudiadas por difracción de rayos X, (DRX y medidas eléctricas. Las fases se sintetizaron por reacción en estado sólido entre los óxidos componentes. La incorporación de los cationes Ni2+ y Co2+,3+ en la red en lugar de Mn lleva a cambios en los parámetros de red y en la simetría de la perovskita, GdMnO3 o del compuesto hexagonal Er

  2. The magnetic anisotropy of Gd-Y alloys

    Science.gov (United States)

    Phu Thuy, Nguyen; Verdonk, H. J.; Menovsky, A.; Franse, J. J. M.; Gersdorf, R.

    1983-02-01

    Magnetic torque curves on single crystals of Gd 1- xY x ( x ⩽ 0.1) show a reduction of the anomalous contribution that was observed in pure Gd, with increasing Y-content. Several explanations of this phenomenon are indicated in this paper.

  3. Photoluminescence related to Gd3+:N-vacancy complex in GaN:Gd multi-quantum wells

    International Nuclear Information System (INIS)

    Almokhtar, Mohamed; Emura, Shuichi; Koide, Akihiro; Fujikawa, Takashi; Asahi, Hajime

    2015-01-01

    Highlights: • We grew Gd-doped GaN multi-quantum wells (MQWs) with quantum layer thickness of one nm by MBE. • The X-ray absorption near edge structure spectra observed at Gd LIII-edge indicate a nitrogen vacancy adjacent to Gd substituting the Ga ion in Gd-doped GaN MQW. • The photoluminescence of the samples is discussed considering the formation of a Gd 3+ :Nitrogen-vacancy complex. • A model is presented considering exciton-polaron formation trapped in defect sites around the Gd 3+ :N-vacancy complex in Gd-doped GaN MQWs. - Abstract: The photoluminescence of Gd-doped GaN multi-quantum wells (MQWs) is presented and discussed considering the formation of a Gd 3+ :Nitrogen-vacancy (N-vacancy) complex. A lower energy photoluminescence peak was observed for the Gd-doped GaN MQW sample with respect to the main peak assigned to a neutral donor bound exciton (D 0 X) of the undoped GaN MQW sample. The X-ray absorption near edge structure spectrum observed at Gd L III -edge indicates a nitrogen vacancy adjacent to the Gd substituting the Ga ion in Gd-doped GaN MQW sample. Local stresses around the Gd dopants in Gd-doped GaN matrix generated due to the larger diameter of the Gd 3+ ion with respect to the Ga 3+ ion can be relieved by the creation of vacancies. The lower formation energy of N-vacancies in GaN matrix introduce them as a preferred candidate to relieve the generated stresses. A Gd 3+ :N-vacancy complex consisting of a Gd 3+ ion and the created nitrogen vacancy adjacent to the Gd 3+ dopant is likely to form in GaN:Gd matrix. The lower photoluminescence peak energy observed in the Gd-doped GaN MQW sample is assigned to the recombination of an exciton captured at the Gd 3+ :N-vacancy complex forming a small polaron-like state. A model is presented considering the small exciton-polaron population in defect sites captured around the Gd 3+ ions in the Gd-doped GaN

  4. Growth and structural, optical, and electrical properties of zincite crystals

    Science.gov (United States)

    Kaurova, I. A.; Kuz'micheva, G. M.; Rybakov, V. B.

    2013-03-01

    An X-ray diffraction study of ZnO crystals grown by the hydrothermal method has revealed reflections that give grounds to assign them to the sp. gr. P3 rather than to P63 mc. The distribution of Zn1, Zn2, O1, and O2 over structural positions, along with vacancies and incorporated zinc atoms, explains the dissymmetrization observed in terms of the kinetic (growth) phase transition of the order-disorder type, which is caused by ordering Zn and O atoms over structural positions. The color of crystals of refined compositions (Zn0.975□0.025)Zn i(0.015)(O0.990□0.010) (green) and (Zn0.965□0.035)Zn i(0.035)O (bright green) is related to different oxygen contents, which is confirmed by the results of electron probe X-ray microanalysis and absorption spectroscopy. The degree of the structural quality of crystals, their resistivity, and activation energy are also related to oxygen vacancies.

  5. The Synthesis and Crystal Structure of Two New Hydrazone Compounds

    Directory of Open Access Journals (Sweden)

    Li-Hua Wang

    2016-05-01

    Full Text Available Two new hydrazone compounds, 4-formylimidazole-4-hydroxybenzhydrazone dihydrate (1 and 2-nitrobenzaldehyde-2-furan formylhydrazone (2, were synthesized via the classical synthesis method. Their structure was determined via elemental analysis and X-ray single crystal diffraction analysis. Compound 1 crystallizes in triclinic, space group P-1 with a = 7.0321(14 Å, b = 7.3723(15 Å, c = 13.008(3 Å, α = 98.66(3°, β = 101.69(3°, γ = 92.25(3°, V = 651.2(2 Å3, Z = 2, Dc = 1.358 g·cm−3, μ = 0.106 mm−1, F(000 = 280, and final R1 = 0.0564, wR2 = 0.1420. Compound 2 crystallizes in monoclinic, space group P21/c with a = 17.3618(9 Å, b = 9.1506(4 Å, c = 15.5801(7 Å, β = 104.532(5°, V = 2396.05(19 Å3, Z = 8, Dc = 1.437 g·cm−3, μ = 0.111 mm−1, F(000 = 1072, and final R1 = 0.0633, wR2 = 0.1649. Compound 1 forms a 2D-layered structure via the interactions of 1D chains and Compound 2 forms a 3D network structure via the interactions of 1D chains.

  6. Programmatic conversion of crystal structures into 3D printable files using Jmol

    OpenAIRE

    Scalfani, Vincent F.; Williams, Antony J.; Tkachenko, Valery; Karapetyan, Karen; Pshenichnov, Alexey; Hanson, Robert M.; Liddie, Jahred M.; Bara, Jason E.

    2016-01-01

    Background Three-dimensional (3D) printed crystal structures are useful for chemistry teaching and research. Current manual methods of converting crystal structures into 3D printable files are time-consuming and tedious. To overcome this limitation, we developed a programmatic method that allows for facile conversion of thousands of crystal structures directly into 3D printable files. Results A collection of over 30,000 crystal structures in crystallographic information file (CIF) format from...

  7. Site preference of metal atoms in Gd_5_-_xM_xTt_4 (M = Zr, Hf; Tt = Si, Ge)

    International Nuclear Information System (INIS)

    Yao, Jinlei; Mozharivskyj, Yurij

    2011-01-01

    Zirconium and hafnium were incorporated into the Gd_5Ge_4 and Gd_5Si_4 parent compounds in order to study the metal-site occupation in the M_5X_4 magnetocaloric phases (M = metals; X = p elements) family. The Gd_5_-_xZr_xGe_4 phases adopt the orthorhombic Sm_5Ge_4-type (space group Pnma) structure for x ≤ 1.49 and the tetragonal Zr_5Si_4-type (P4_12_12) structure for x ≥ 1.77. The Gd_5_-_xHf_xSi_4 compounds crystallize in the orthorhombic Gd_5Si_4-type (Pnma) structure for x ≤ 0.41 and the Zr_5Si_4-type structure for x ≥ 0.7. In both systems, single-crystal X-ray diffraction reveals that the Zr/Hf atoms preferentially occupy the slab-surface M2 and slab-center M3 sites, both of which have a significantly larger Zr/Hf population than the slab-surface M1 site. The metal-site preference, i.e. the coloring problem on the three metal sites, is discussed considering geometric and electronic effects of the local coordination environments. The analysis of the metal-site occupation in Gd_5_-_xZr_xGe_4 and Gd_5_-_xHf_xSi_4 as well as other metal-substituted M_5X_4 systems suggests that both geometric and electronic effects can be used to explain the metal-site occupation. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Ab initio molecular crystal structures, spectra, and phase diagrams.

    Science.gov (United States)

    Hirata, So; Gilliard, Kandis; He, Xiao; Li, Jinjin; Sode, Olaseni

    2014-09-16

    Conspectus Molecular crystals are chemists' solids in the sense that their structures and properties can be understood in terms of those of the constituent molecules merely perturbed by a crystalline environment. They form a large and important class of solids including ices of atmospheric species, drugs, explosives, and even some organic optoelectronic materials and supramolecular assemblies. Recently, surprisingly simple yet extremely efficient, versatile, easily implemented, and systematically accurate electronic structure methods for molecular crystals have been developed. The methods, collectively referred to as the embedded-fragment scheme, divide a crystal into monomers and overlapping dimers and apply modern molecular electronic structure methods and software to these fragments of the crystal that are embedded in a self-consistently determined crystalline electrostatic field. They enable facile applications of accurate but otherwise prohibitively expensive ab initio molecular orbital theories such as Møller-Plesset perturbation and coupled-cluster theories to a broad range of properties of solids such as internal energies, enthalpies, structures, equation of state, phonon dispersion curves and density of states, infrared and Raman spectra (including band intensities and sometimes anharmonic effects), inelastic neutron scattering spectra, heat capacities, Gibbs energies, and phase diagrams, while accounting for many-body electrostatic (namely, induction or polarization) effects as well as two-body exchange and dispersion interactions from first principles. They can fundamentally alter the role of computing in the studies of molecular crystals in the same way ab initio molecular orbital theories have transformed research practices in gas-phase physical chemistry and synthetic chemistry in the last half century. In this Account, after a brief summary of formalisms and algorithms, we discuss applications of these methods performed in our group as compelling

  9. Molecular complex of lumiflavin and 2-aminobenzoic acid: crystal structure, crystal spectra, and solution properties.

    Science.gov (United States)

    Shieh, H S; Ghisla, S; Hanson, L K; Ludwig, M L; Nordman, C E

    1981-08-04

    The molecular complex lumiflavin-2-aminobenzoic acid monohydrate (C13H12N4O2.C7H7NO2.H2O) crystallizes from from aqueous solution as red triclinic prisms. The space group is P1 with cell dimensions a = 9.660 A, b = 14.866 A, c = 7.045 A, alpha = 95.44 degrees , beta = 95.86 degrees, and gamma = 105.66 degrees . The crystal structure was solved by direct methods and refined by block-diagonal least-squares procedures to an R value of 0.050 on the basis of 1338 observed reflections. The structure is composed of stacks of alternating lumiflavin adn un-ionized (neutral) 2-aminobenzoic acid molecules. Two different modes of stacking interaction are observed. In one, 2-aminobenzoic acid overlaps all three of the isoalloxazine rings, at a mean distance of 3.36 A; in the other, 2-aminobenzoic acid interacts distance of 3.36 A; in the other, 2-aminobenzoic acid interacts with the pyrazine and dimethylbenzene moieties, at a distance of 3.42 A. Perpendicular to the stacking direction, the molecules form a continuous sheet. Each flavin is hydrogen bonded via O(2) and NH(3) to two symmetrically related aminobenzoates; the water of crystallization forms three hydrogen bonds, bridging two flavins, via O(4) and N(5), and one aminobenzoic acid. The red color of the crystals results from a charge-transfer transition involving stacked flavin and 2-aminobenzoic acid. The red color of the crystals results from a charge-transfer transition involving stacked flavin and 2-aminobenzoic acid molecules. Measurements of the polarized optical absorption spectra of crystals show that the transition moment direction for the long wavelength absorbance (beyond 530 nm) contains an out-of-plane component which can only arise from a charge-transfer interaction. Since the amino N does not make exceptionally close interactions with isoalloxazine atoms in either stacking mode (minimum interatomic distance 3.52 A), the charge transfer is presumed to involve pi orbitals of the 2-aminobenzoic acid donor.

  10. RE{sub 3}Au{sub 5}Zn (RE = Y, Sm, Gd-Ho). A new structure type with five- and six-membered rings as building units in a gold network

    Energy Technology Data Exchange (ETDEWEB)

    Gerke, Birgit; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie and NRW Graduate School of Chemistry

    2016-08-01

    RE{sub 3}Au{sub 5}Zn (RE = Y, Sm, Gd-Ho) intermetallic compounds were synthesized by melting the elements in sealed tantalum tubes. They exhibit a new structure type which was studied by X-ray diffraction on powders and refined from single crystal diffraction data: Cmcm, a = 736.9(2), b = 1489.4(2), c = 1330.4(3) pm, wR2 = 0.0371, 1184 F{sup 2} values and 55 variables for Y{sub 3}Au{sub 4.92}Zn{sub 1.08} and a = 739.0(1), b = 1495.8(2), c = 1339.2(2) pm, wR2 = 0.0325, 1410 F{sup 2} values and 54 variables for Tb{sub 3}Au{sub 5}Zn. The network consists of five- and six-membered gold rings in puckered conformations. Atoms of the rare earth elements are placed within the cavities of this network where every third cavity is filled by a Zn{sub 2} dumbbell. The structure is discussed in detail and compared with the gold substructure of Hf{sub 7}Au{sub 10}.

  11. Evidence for existence of spin glass state in single phase polycrystalline Gd0.99Sr0.01MnO3 through structural and magnetic properties

    International Nuclear Information System (INIS)

    Joy, Lija K.; Anantharaman, M.R.; Thomas, Senoy

    2013-01-01

    Single phase rare earth manganites have attracted scientific interest due to their interesting magnetic, electrical and structural properties. Bulk GdMnO 3 has metamagnetic features with a transition from antiferromagnetic to weak-ferromagnetic state upon cooling. Recently we have found promising magnetic behaviour when GdMnO 3 is doped with strontium. Magnetic behaviour of doped rare earth manganites in the form of Gd 1-x SrMnO 3 has attracted scientific interest due to their promising technological applications in data storage, as catalysts, as electrode materials and sensors. Irreversibility and sharp anomalies has been observed in the magnetization studies of polycrystalline Gd 0.99 Sr 0.01 MnO 3 perovskite synthesized by wet solid state reaction method. X-ray diffraction pattern of the system confirms the single phase orthorhombically distorted perovskite structure. The Field Cooled (FC) and Zero Field Cooled (ZFC) magnetization obtained as a function of temperature with external magnetic field 25Oe, 50Oe, and 200Oe showed thermal irreversibility along with a cusp below the ordering temperature indicating the appearance of spin glass state. The origin of this spin glass state is attributed to spin frustrations, due to the rare earth ions forming a deformed Kagome lattice. Under a magnetic field of 25Oe, the splitting between FC and ZFC magnetization is observed at 70K with a cusp in M ZFC at 45K and when the field is increased to 50Oe and 200Oe, the splitting becomes narrower and shows a shift in the irreversible temperature (T irr ) to lower temperatures 59K and 50K respectively. The spins are frozen in random directions due to a lack of long range magnetic interactions, when the system is cooled through its freezing temperature T f to T f . Room temperature variation of magnetization with applied field indicates the existence of ferromagnetic clusters of glass over antiferromagnetic background. Thermal irreversibility between FC and ZFC below T irr with a

  12. Superconductivity degradation in Gd-containing high temperature superconductors (HTSC) under thermal neutron irradiation

    International Nuclear Information System (INIS)

    Petrov, A.; Kudrenitskis, I.; Makletsov, A.; Arhipov, A.; Karklin, N.

    1999-01-01

    The physical properties of ordered crystals are extremely sensitive to the degree of order in the distribution of the various kinds of atoms over the corresponding sites in the crystal lattice. An increasingly popular means of creating disordered states is to use nuclear radiation. The type of radiation defects which appear and the nature and degree of the structural changes in ordered crystals depend on the kind of radiation and the fluence level, the irradiation temperature, the type of crystal structure, the composition and initial disorder of the material, the character of the interatomic forces, etc. There are many such scientific publications where the effects of fast neutron irradiation on high temperature superconductors (HTSC) have been studied in both polycrystalline and single crystalline superconductors. It is known also that the role of thermal neutrons in structural defects forming is negligible in comparison with fast neutrons because of their small (∼0.025 eV) energy. But it is evident enough that in superconductors containing isotopes with large thermal neutron cross sections the important results concerning the role of point defects could be obtained. Such point defects are creating due to soft displacements of isotopes having interacted with thermal neutrons. Such the possibility of creating point defects in solids including HTSC is investigating by several groups (Austria, USA, China, Latvia) and these investigations have found the support in the person of IAEA. In this review the authors consider the changes brought about by thermal-neutron irradiation (E∼0.025 eV) in the structure, superconducting and magnetic properties of gadolinium containing ordered HTSC with the structure 123, whose extreme electric and magnetic properties continue to attract both research and practical interest. All of the studies reviewed have been done on bulk polycrystalline samples RBa 2 Cu 3 O 7-δ (where R - natural mixture of Gd isotopes, 155 Gd, 157 Gd, 160

  13. Ternary gallides RE{sub 4}Rh{sub 9}Ga{sub 5}, RE{sub 5}Rh{sub 12}Ga{sub 7} and RE{sub 7}Rh{sub 18}Ga{sub 11} (RE=Y, La-Nd, Sm, Gd, Tb). Intergrowth structures with MgCu{sub 2} and CaCu{sub 5} related slabs

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, Stefan; Rodewald, Ute C.; Poettgen, Rainer [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Univ. Oldenburg (Germany). Inst. fuer Chemie

    2017-07-01

    Fourteen ternary gallides RE{sub 4}Rh{sub 9}Ga{sub 5}, RE{sub 5}Rh{sub 12}Ga{sub 7} and RE{sub 7}Rh{sub 18}Ga{sub 11} (RE=Y, La-Nd, Sm, Gd, Tb) were synthesized from the elements by arc-melting, followed by different annealing sequences either in muffle or induction furnaces. The samples were characterized through Guinier powder patterns and the crystal structures of Ce{sub 4}Rh{sub 9}Ga{sub 5}, Ce{sub 5}Rh{sub 12}Ga{sub 7}, Ce{sub 7}Rh{sub 18}Ga{sub 11}, Nd{sub 5}Rh{sub 10.44(4)}Ga{sub 8.56(4)}, Nd{sub 4}Rh{sub 9}Ga{sub 5} and Gd{sub 4}Rh{sub 9}Ga{sub 5} were refined from single crystal X-ray diffractometer data. The new gallides are the n=2, 3 and 5 members of the RE{sub 2+n} Rh{sub 3+3n} Ga{sub 1+2n} structure series in the Parthe intergrowth concept. The slabs of these intergrowth structures derive from the cubic Laves phase MgCu{sub 2} (Mg{sub 2}Ni{sub 3}Si as ternary variant) and CaCu{sub 5} (CeCo{sub 3}B{sub 2} as ternary variant). Only the Nd{sub 5}Rh{sub 10.44(4)}Ga{sub 8.56(4)} crystal shows Rh/Ga mixing within the Laves type slabs. Magnetic susceptibility measurements reveal Pauli paramagnetism for Y{sub 4}Rh{sub 9}Ga{sub 5} and Curie-Weiss paramagnetism for Gd{sub 4}Rh{sub 9}Ga{sub 5} and Tb{sub 4}Rh{sub 9}Ga{sub 5}. Low-temperature data show ferromagnetic ordering at T{sub C}=78.1 (Gd{sub 4}Rh{sub 9}Ga{sub 5}) and 55.8 K (Tb{sub 4}Rh{sub 9}Ga{sub 5}).

  14. Crystal structure of inactive form of Rab3B

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei [Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Huazhong Normal University, Wuhan 430079 (China); Shen, Yang [Structural Genomics Consortium, University of Toronto, 101 College St., Toronto, Ontario, Canada M5G 1L7 (Canada); Jiao, Ronghong [Department of Function Inspection, Hebei Provincial People' s Hospital, Shijiazhuang 050051 (China); Liu, Yanli; Deng, Lingfu [Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Huazhong Normal University, Wuhan 430079 (China); Qi, Chao, E-mail: qichao@mail.ccnu.edu.cn [Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Huazhong Normal University, Wuhan 430079 (China)

    2012-02-24

    Highlights: Black-Right-Pointing-Pointer This is the first structural information of human Rab3B. Black-Right-Pointing-Pointer To provides a structural basis for the GDP/GTP switch in controlling the activity of Rab3. Black-Right-Pointing-Pointer The charge distribution of Rab3B indicates its unique roles in vesicular trafficking. -- Abstract: Rab proteins are the largest family of ras-related GTPases in eukaryotic cells. They act as directional molecular switches at membrane trafficking, including vesicle budding, cargo sorting, transport, tethering, and fusion. Here, we generated and crystallized the Rab3B:GDP complex. The structure of the complex was solved to 1.9 A resolution and the structural base comparison with other Rab3 members provides a structural basis for the GDP/GTP switch in controlling the activity of small GTPase. The comparison of charge distribution among the members of Rab3 also indicates their different roles in vesicular trafficking.

  15. Crystal structure of inactive form of Rab3B

    International Nuclear Information System (INIS)

    Zhang, Wei; Shen, Yang; Jiao, Ronghong; Liu, Yanli; Deng, Lingfu; Qi, Chao

    2012-01-01

    Highlights: ► This is the first structural information of human Rab3B. ► To provides a structural basis for the GDP/GTP switch in controlling the activity of Rab3. ► The charge distribution of Rab3B indicates its unique roles in vesicular trafficking. -- Abstract: Rab proteins are the largest family of ras-related GTPases in eukaryotic cells. They act as directional molecular switches at membrane trafficking, including vesicle budding, cargo sorting, transport, tethering, and fusion. Here, we generated and crystallized the Rab3B:GDP complex. The structure of the complex was solved to 1.9 Å resolution and the structural base comparison with other Rab3 members provides a structural basis for the GDP/GTP switch in controlling the activity of small GTPase. The comparison of charge distribution among the members of Rab3 also indicates their different roles in vesicular trafficking.

  16. Facile synthesis of gold nanomaterials with unusual crystal structures.

    Science.gov (United States)

    Fan, Zhanxi; Huang, Xiao; Chen, Ye; Huang, Wei; Zhang, Hua

    2017-11-01

    Gold (Au) nanomaterials have attracted wide research attention, owing to their high chemical stability, promising catalytic properties, excellent biocompatibility, unique electronic structure and outstanding localized surface plasmon resonance (LSPR) absorption properties; all of which are closely related to their size and shape. Recently, crystal-phase-controlled synthesis of noble metal nanomaterials has emerged as a promising strategy to tune their physicochemical properties. This protocol describes the detailed experimental procedures for the crystal-phase-controlled syntheses of Au nanomaterials with unusual crystal structures under mild conditions. Briefly, pure hexagonal close-packed (hcp) Au square sheets (AuSSs) with a thickness of ∼2.4 nm are synthesized using a graphene-oxide-assisted method in which HAuCl 4 is reduced by oleylamine in a mixture of hexane and ethanol. By using pure hexane as the solvent, well-dispersed ultrathin hcp/face-centered cubic (fcc) Au nanowires with a diameter of ∼1.6 nm on graphene oxide can be obtained. Meanwhile, hcp/fcc Au square-like plates with a side length of 200-400 nm are prepared via the secondary growth of Au on the hcp AuSSs. Remarkably, hexagonal (4H) Au nanoribbons with a thickness of 2.0-6.0 nm can be synthesized with a one-pot colloidal method in which HAuCl 4 is reduced by oleylamine in a mixed solvent of hexane and 1,2-dichloropropane. It takes 17-37 h for the synthesis of these Au nanomaterials with unusual crystal structures. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) are used to characterize the resultant Au nanomaterials, which could have many promising applications, such as biosensing, near-IR photothermal therapy, catalysis and surface-enhanced Raman scattering (SERS).

  17. NMR measurements in milled GdCo2 and GdFe2 intermetallic compounds

    International Nuclear Information System (INIS)

    Tribuzy, C.V.B.; Guimaraes, A.P.; Biondo, A.; Larica, C.; Alves, K.M.B.

    1998-12-01

    We have used the nuclear magnetic resonance technique to study the magnetic and structural properties of the Gd-Co and Gd-Fe metallic systems, starting with the C15 laves phase intermetallic compounds, and submitting them to a high energy milling process. This leads to the amorphization of the samples, as determined by the X-ray diffraction spectra. For the Gd-Co system the NMR study used the 59 Co nucleus; in the Gd-Fe system, 155,157 Gd and 57 Fe were used. Both systems showed segregation of the pure elements, after a few hours of milling. In the Gd-Co system, a single line, of increasing width, was observed in the 59 Co spectrum. In the Gd-Fe system, the 155 Gd and 157 Gd resonances show three lines, arising from electrical quadrupole interaction. With increasing milling time, the lines broaden, and extra lines appear attributed to a cubic phase of Gd; this interpretation is supported by the X-ray analysis of the samples. The 57 Fe NMR spectrum of this system also informs on the direction of magnetization of the samples in the early stages of milling. From 1 h to 7 h of milling, a spectrum of α-Fe was observed. The study of the NMR line intensity as a function of radio frequency (r.f.) power in Gd Co 2 suggests the existence of regions of the samples with different degrees of disorder. We have observed the persistence of NMR signals from the original intermetallic compounds in the samples with up to 10 h and 7 h of milling, respectively, for Gd Co 2 and Gd Fe 2 . (author)

  18. Crystal Structure of the Yeast Nicotinamidase Pnc1p

    OpenAIRE

    Hu, Gang; Taylor, Alexander B.; McAlister-Henn, Lee; Hart, P. John

    2007-01-01

    The yeast nicotinamidase Pnc1p acts in transcriptional silencing by reducing levels of nicotinamide, an inhibitor of the histone deacetylase Sir2p. The Pnc1p structure was determined at 2.9 Å resolution using MAD and MIRAS phasing methods after inadvertent crystallization during the pursuit of the structure of histidine-tagged yeast isocitrate dehydrogenase (IDH). Pnc1p displays a cluster of surface histidine residues likely responsible for its co-fractionation with IDH from Ni2+-coupled chro...

  19. Topological Characterization of Carbon Graphite and Crystal Cubic Carbon Structures.

    Science.gov (United States)

    Siddiqui, Wei Gao Muhammad Kamran; Naeem, Muhammad; Rehman, Najma Abdul

    2017-09-07

    Graph theory is used for modeling, designing, analysis and understanding chemical structures or chemical networks and their properties. The molecular graph is a graph consisting of atoms called vertices and the chemical bond between atoms called edges. In this article, we study the chemical graphs of carbon graphite and crystal structure of cubic carbon. Moreover, we compute and give closed formulas of degree based additive topological indices, namely hyper-Zagreb index, first multiple and second multiple Zagreb indices, and first and second Zagreb polynomials.

  20. Band structures in the nematic elastomers phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuai [Department of Mechanics, School of Civil Engineering, Beijing Jiaotong University, Beijing 100044 (China); School of Civil Engineering and Architecture, Anyang Normal University, Anyang 455000 (China); Liu, Ying, E-mail: yliu5@bjtu.edu.cn [Department of Mechanics, School of Civil Engineering, Beijing Jiaotong University, Beijing 100044 (China); Liang, Tianshu [Department of Mechanics, School of Civil Engineering, Beijing Jiaotong University, Beijing 100044 (China)

    2017-02-01

    As one kind of new intelligent materials, nematic elastomers (NEs) represent an exciting physical system that combines the local orientational symmetry breaking and the entropic rubber elasticity, producing a number of unique physical phenomena. In this paper, the potential application of NEs in the band tuning is explored. The band structures in two kinds of NE phononic crystals (PCs) are investigated. Through changing NE intrinsic parameters, the influence of the porosity, director rotation and relaxation on the band structures in NE PCs are analyzed. This work is a meaningful try for application of NEs in acoustic field and proposes a new intelligent strategy in band turning.