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Chlorido(4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine)platinum(II) chloride toluene monosolvate

Description: In the title compound, [PtCl(C₂₇H₃₅N₃)]Cl·C₇H₈, the Ptᴵᴵ atom is coordinated in a pseudo-square-planar fashion by the N atoms of a 4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine ligand and a Cl atom.
Date: November 22, 2010
Creator: Batrice, Rami J.; Nesterov, Vladimir N. & Smucker, Bradley W.
Partner: UNT College of Arts and Sciences

Automated Structure Solution with the PHENIX Suite

Description: Significant time and effort are often required to solve and complete a macromolecular crystal structure. The development of automated computational methods for the analysis, solution and completion of crystallographic structures has the potential to produce minimally biased models in a short time without the need for manual intervention. The PHENIX software suite is a highly automated system for macromolecular structure determination that can rapidly arrive at an initial partial model of a structure without significant human intervention, given moderate resolution and good quality data. This achievement has been made possible by the development of new algorithms for structure determination, maximum-likelihood molecular replacement (PHASER), heavy-atom search (HySS), template and pattern-based automated model-building (RESOLVE, TEXTAL), automated macromolecular refinement (phenix.refine), and iterative model-building, density modification and refinement that can operate at moderate resolution (RESOLVE, AutoBuild). These algorithms are based on a highly integrated and comprehensive set of crystallographic libraries that have been built and made available to the community. The algorithms are tightly linked and made easily accessible to users through the PHENIX Wizards and the PHENIX GUI.
Date: June 9, 2008
Creator: Zwart, Peter H.; Zwart, Peter H.; Afonine, Pavel; Grosse-Kunstleve, Ralf W.; Hung, Li-Wei; Ioerger, Tom R. et al.
Partner: UNT Libraries Government Documents Department

Crystal structure of kappa-In2Se3

Description: Structural properties of single-phase films of {kappa}-In{sub 2}Se{sub 3} and {gamma}-In{sub 2}Se{sub 3} were investigated. Both films were polycrystalline but their microstructure differed considerably. The a-lattice parameter of {kappa}-In{sub 2}Se{sub 3} has been measured. Comparison between these two materials indicates that {kappa}-In{sub 2}Se{sub 3} has a significantly larger unit cell ({Delta}c = 2.5 {+-} 0.2 % and {Delta}a = 13.5 {+-} 0.5%) and a structure more similar to the {alpha}-phase of In{sub 2}Se{sub 3}.
Date: October 24, 2002
Creator: Jasinski, J.; Swider, W.; Washburn, J.; Liliental-Weber, Z.; Chaiken, A.; Nauka, K. et al.
Partner: UNT Libraries Government Documents Department

Removal of pertechnetate from simulated nuclear waste streams using supported zerovalent iron

Description: The application of nanoparticles of predominantly zerovalent iron (nanoiron), either unsupported or supported, to the separation and reduction of pertechnetate anions (TcO4-) from complex waste mixtures was investigated as an alternative approach to current waste-processing schemes. Although applicable to pertechnetate-containing waste streams in general, the research discussed here was directed at two specific potential applications at the U.S. Department of Energy's Hanford Site: (1) the direct removal of pertechnetate from highly alkaline solutions, typical of those found in Hanford tank waste, and (2) the removal of dilute pertechnetate from near-neutral solutions, typical of the eluate streams from commercial organic ion-exchange resins that may be used to remediate Hanford tank wastes. It was envisioned that both applications would involve the subsequent encapsulation of the loaded sorbent material into a separate waste form. A high surface area (>200 M2/g) base-stable, nanocrystalline zirconia was used as a support for nanoiron for tests with highly alkaline solutions, while a silica gel support was used for tests with near-neutral solutions. It was shown that after 24 h of contact time, the high surface area zirconia supported nanoiron sorbent removed about 50percent (K-d = 370 L/kg) of the pertechnetate from a pH 14 tank waste simulant containing 0.51 mM TCO4- and large concentrations of Na+, OH-, NO3-, and CO32- for a phase ratio of 360 L simulant per kg of sorbent. It was also shown that after 18 h of contact time, the silica-supported nanoiron removed>95percent pertechnetate from a neutral pH eluate simulant containing 0.076 mM TcO4_ for a phase ratio of 290 L/kg. It was determined that in all cases, nanoiron reduced the Tc(VII) to Tc(IV), or possibly to Tc(V), through a redox reaction. Finally, it was demonstrated that a mixture of 20 mass percent of the solid reaction products obtained from contacting zirconia- supported ...
Date: July 11, 2007
Creator: Darab, John; Amonette, Alexandra; Burke, Deborah; Orr, Robert; Ponder, Sherman; Schrick, Bettina et al.
Partner: UNT Libraries Government Documents Department

Effect of pressure on the crystal structure of ettringite

Description: X-ray diffraction and infrared data have been collected froma sample of ettringite from ambient pressure to 6.4 GPa. The sample wasfound to reversibly transform to an amorphous phase at 3 GPa. Theisothermal bulk modulus of ettringite was found to be 27(7) GPa and theincompressibilities of the lattice parameters were found to be 71(30) GPaalong a and 108(36) GPa along c.
Date: December 8, 2006
Creator: Clark, Simon M.; Colas, Bruno; Kunz, Martin; Speziale, Sergio & Monteiro, Paulo J.M.
Partner: UNT Libraries Government Documents Department

Crystal phases and lattice dynamics of slip-cast {beta}{prime}-sialons

Description: The crystal structures and phonon densities of states (DOS) of {beta}{prime}-Sialon ceramics, Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} (O {le} z {le} 6), prepared by a novel slip-cast method were studied by neutron scattering techniques. A Rietveld analysis of the diffraction patterns shows that samples of z < 4 form a single-phase solid solution of Si-Al-O-N isostructural to {beta}-Si{sub 3}N{sub 4} (space group P6{sub 3}/m). Within this structure there is a consistent preferred occupation of O on the 2c sites and N on the 6h sites. For z > 4 the materials exhibit multiple-phase structure. The observed phonon DOS of the O {le} z {le} 4 ceramics displays phonon bands at about 50 and 115 meV. These features are considerably broader than the corresponding ones in {beta}-Si{sub 3}N{sub 4} powder. As z increases, effects due to atomic disorder lead to an overlap of the two phonon bands and a complete fill up of the phonon gap at {approximately} 100 meV observed in Si{sub 3}N{sub 4}.
Date: December 31, 1995
Creator: Loong, C.K.; Richardson, J.W. Jr.; Suzuki, S. & Ozawa, M.
Partner: UNT Libraries Government Documents Department

TEM investigation on the low temperature phase of HfV{sub 2}

Description: HfV2, a particularly attractive C15 Laves phase structural material, undergoes a structural transformation at 115K. A tentative reciprocal lattice for low-temperature HfV2 based on a combination of selected area diffraction patterns is illustrated. The results reveal structural characteristics inconsistent with earlier claims by other investigators. Further and detailed studies are under way, using a combination of CBED and synchrotron diffraction to determine the low-temperature structure`s crystal symmetry, lattice parameters, and atomic positions.
Date: April 1, 1995
Creator: Chu, Fuming & Mitchell, T.E.
Partner: UNT Libraries Government Documents Department

Shape from equal thickness contours

Description: A unique imaging modality based on Equal Thickness Contours (ETC) has introduced a new opportunity for 3D shape reconstruction from multiple views. We present a computational framework for representing each view of an object in terms of its object thickness, and then integrating these representations into a 3D surface by algebraic reconstruction. The object thickness is inferred by grouping curve segments that correspond to points of second derivative maxima. At each step of the process, we use some form of regularization to ensure closeness to the original features, as well as neighborhood continuity. We apply our approach to images of a sub-micron crystal structure obtained through a holographic process.
Date: May 10, 1998
Creator: Cong, G. & Parvin, B.
Partner: UNT Libraries Government Documents Department

Directional Ordering and Dynamics in Dusty Plasmas

Description: We use molecular dynamics (MD) simulation methods to investigate dusty plasma crystal structure, with the grains subject to a spherically symmetric Debye-Hueckel potential, a uni-directional external potential and an asymmetric wake potential. The structure is studied as a function of Mach number and magnitude of the wake as well as the strength of the rf input power, using parameters from a self-consistent dust-sheath model.
Date: May 24, 1999
Creator: Hammerberg, J. E.; Holian, B. L.; Murillo, M. S. & Winske, D.
Partner: UNT Libraries Government Documents Department

Characterization of a mixed salt of 1-hydroxy-pyridin-2-one Pu(IV)complexes

Description: Most expert analyses of the projected world energy needs show utilization of nuclear energy will be essential for the next few decades, and hence the need to support this technology grows. But as one measure of the supporting science base of this field, as of December 2006, only 25 Pu containing structures were in the Cambridge Structural Database, as compared to 21,807 for Fe. A comparison of the rate of addition to this knowledge base reveals that approximately 500 Fe structures are registered with the Cambridge Structural Database every year, while in the same period only two or three Pu crystal structures are published. A continuing objective of this laboratory has been the development of new sequestering agents for actinide decorporation and selective extractions. This effort has been based on similarities in the properties of Pu(IV) and Fe(III), and the chelating groups in microbial Fe(III) sequestering agents, siderophores. The HOPO ligands (Figure 1) are one such class of chelating group which have been investigated as selective actinide extractants.
Date: January 9, 2007
Creator: Gorden, Anne E.V.; Xu, Jide; Szigethy, Geza; Oliver, Allen; Shuh,David K. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

Orientation imaging microscopy investigation of the compression deformation of a [011] ta single crystal

Description: High-purity tantalum single crystal cylinders oriented with [110] parallel to the cylinder axis were deformed 10, 20, and 30 percent in compression. The samples were subsequently sectioned for characterization using Orientation Imaging Microscopy (O&I) along two orthogonal sectioning planes: one in the plane containing [001] and [110] (longitudinal) and the other in the plane containing [1{anti 1}0] and[110] (transverse). To examine local lattice rotations, the Euler angles relative to a reference angle at the section center were decomposed to their in-plane and out-of-plane components. The in-plane and out-of-plane misorientation maps for all compression tests reveal inhomogeneous deformation everywhere and particularly large lattice rotations in the comers of the longitudinal section. Of particular interest are the observed alternating orientation changes. This suggests the existence of networks of dislocations with net alternating sign that are required to accommodate the observed rotations. Rotation maps from the transverse section are distinctly different in appearance from those in the longitudinal plane. However, the rotation maps confirm that the rotations observed above were about the [1{anti 1}0] axis. Alternating orientation changes are also observed on this section. Results will be directly compared with crystal rotations predicted using finite element methods and reviewed in light of the LLNL Multiscale Materials Modeling Program.
Date: January 8, 1999
Creator: Adams, B L; Campbell, G H; King, W E; Lassila, D H; Stolken, J S; Sun, S et al.
Partner: UNT Libraries Government Documents Department

Crystal and magnetic structure of stoichiometric YFe{sub 2}O{sub 4}

Description: Crystal structure of stoichiometric YFe{sub 2}O{sub 4} powder was studied by high-resolution neutron diffraction at room temperature, 225 K and 80 K. Rietveld refinements of the diffraction patterns give reasonable fits with space group R{bar 3}m (hexagonal) for room temperature, and with P{bar 1} (triclinic) for 225 K. However, the 80 K pattern cannot be fitted at all with the same triclinic symmetry, indicating that the structure is much more complicated. The magnetic reflection has been separated from those complex nuclear peaks by the polarization analysis. The magnetic structure is also fairly complicated both at 225 K and at 80 K.
Date: August 1, 1994
Creator: Katano, S.; Funahashi, S.; Matsumoto, T.; Iida, J.; Tanaka, M. & Cable, J.W.
Partner: UNT Libraries Government Documents Department

High-temperature annealing of natural UO{sub 2+x}

Description: Four powdered samples of natural UO{sub 2+x} (uraninite) were annealed in a reducing atmosphere up to 1200 C. Initial unit cell parameters ranged from a{sub o}=0.5463 to 0.5385 nm. Small amounts of UO{sub 2.25} occur in all samples after annealing. Annealing curves show effects of recovery of point defects in the oxygen sublattice, ordering of U{sup 4+} and U{sup 6+}, vacancy migration in the cation sublattice, and second order phase transformations. Difference in annealing behavior of UO{sub 2+x} with x<0.15 as compared to x=0.25 between 400 and 700 C is due to ordering of U{sup 4+} and U{sup 6+}. Density increased after annealing except for one sample in which a large number of cavities (1-2{mu}m) formed. Oxidation and chemical composition have a more dramatic effect on the structural state of natural UO{sub 2+x} than self-irradiation caused by {alpha}-decay damage.
Date: December 31, 1990
Creator: Janeczek, J. & Ewing, R.C.
Partner: UNT Libraries Government Documents Department

Investigation of 2D laterally dispersive photonic crystal structures : LDRD 33602 final report.

Description: Artificially structured photonic lattice materials are commonly investigated for their unique ability to block and guide light. However, an exciting aspect of photonic lattices which has received relatively little attention is the extremely high refractive index dispersion within the range of frequencies capable of propagating within the photonic lattice material. In fact, it has been proposed that a negative refractive index may be realized with the correct photonic lattice configuration. This report summarizes our investigation, both numerically and experimentally, into the design and performance of such photonic lattice materials intended to optimize the dispersion of refractive index in order to realize new classes of photonic devices.
Date: December 1, 2003
Creator: Subramania,Ganapathi Subramanian; Vawter, Gregory Allen; Wendt, Joel Robert; Peake, Gregory Merwin; Guo, Junpeng; Peters, David William et al.
Partner: UNT Libraries Government Documents Department

Optical properties of colloidal germanium nanocrystals

Description: Highly crystalline germanium (Ge) nanocrystals in the size range 2--10 nm were grown in inverse micelles and purified and size-separated by high pressure liquid chromatography with on-line optical and electrical diagnostics. The nanocrystals retain the diamond structure of bulk Ge down to at least 2.0 nm (containing about 150 Ge atoms). The background- and impurity-free extinction and photoluminescence (PL) spectra of these nanocrystals revealed rich structure which was interpreted in terms of the bandstructure of Ge shifted to higher energies by quantum confinement. The shifts ranged from {minus}0.1 eV to over 1 eV for the various transitions. PL in the range 350--700 nm was observed from nanocrystals 2--5 nm in size. The 2.0 nm nanocrystals yielded the most intense PL (at 420 nm) which is believed to be intrinsic and attributed to direct recombination at {Gamma}. Excitation at high energy (250 nm) populates most of the conduction bands resulting in competing recombination channels and the observed broad PL spectra.
Date: May 1, 2000
Partner: UNT Libraries Government Documents Department

Self-Diffusion Along Step-Bottoms on Pt(111)

Description: First-principles total energies of periodic vicinals are used to estimate barriers for Pt-adatom diffusion along straight and kinked steps on Pt(111), and around a corner where straight steps intersect. In all cases studied, hopping diffusion has a lower barrier than concerted substitution. In conflict with simulations of dendritic Pt island formation on Pt(111), hopping from a corner site to a step whose riser is a (111)-micro facet is predicted to be more facile than to one whose riser is a (100).
Date: April 5, 1999
Creator: Feibelman, P.J.
Partner: UNT Libraries Government Documents Department

Synthesis, structure and properties of (CN{sub 3}H{sub 6}){sub 4}Zn{sub 3}(SeO{sub 3}){sub 5}, the first organically-templated selenite

Description: An astonishing variety of inorganic networks templated by organic species have been reported over the last 10 years. A great deal of attention has been paid to the structure-directing role of the organic species, and the structural effect of variously coordinated cations, for example distorted octahedral vanadium and pyramidal tin. Less exploratory work has been carried out on the anionic part of the inorganic network, and most groups reported so far (phosphate, germanate, etc.) invariably adopt tetrahedral coordination. The possibilities of incorporating the pyramidal [HP0{sub 3}]{sup 2{minus}} hydrogen phosphite group into extended structures templated by inorganic, alkaline earth cations was explored a few years ago. In this paper the authors report the synthesis, crystal structure, and some properties of (CN{sub 3}H{sub 6}){sub 4}{center_dot}Zn{sub 3}(SeO{sub 3}){sub 5}, the first organically-templated phase to contain the pyramidal selenite [SeO{sub 3}]{sup 2{minus}} anion.
Date: May 22, 2000
Partner: UNT Libraries Government Documents Department

Syntheses and Structures of the Open-Framework Phases (CH(3)NH(3))(3).Zn(4)O(AsO(4))(3) and (CH(3)NH(3))(3).Zn(4)O(PO(4))(3) Related to the M(3)Zn(4)O(XO(4)(3).nH(2)O Family

Description: The solution-mediated syntheses and single crystal structures of (CH<sub>3</sub>NH<sub>3</sub>)<sub>3</sub>&middot;Zn<sub>4</sub>0(AsO<sub>4</sub>)<sub>3</sub> and (CH<sub>3</sub>NH<sub>3</sub>)<sub>3</sub>&middot;Zn<sub>4</sub>O(P0<sub>4</sub>)<sub>3</sub> are reported. These compounds are built up from vertex-sharing three-dimensional Zn0<sub>4</sub> + AsO<sub>4</sub>/P0<sub>4</sub> tetrahedral frameworks encapsulating methylammonium cations in three-dimensional channel systems. These phases are closely related to the zeolite- like M<sub>3</sub>Zn<sub>4</sub>O(XO<sub>4</sub>)<sub>3</sub>&middot;nH<sub>2</sub>O family of phases. Crystal data for (CH<sub>3</sub>NH<sub>3</sub>)<sub>3</sub>&middot;Zn<sub>4</sub>0(AsO<sub>4</sub>)<sub>3</sub>, M, = 790.47, monoclinic, space group P2<sub>1</sub> (No. 4), a = 7.814 (3)&Aring;, b = 15.498 (6)&Aring;, c = 7.815 (3) &Aring;, {beta} = 92.91 (2)0, V = 945.1 (9) &Aring;<sup>3</sup>, Z = 2, R(F) = 3.01%, R<sub>W</sub>(F) = 3.98% (2301 reflections, 236 parameters). Crystal data for (CH<sub>3</sub>NH<sub>3</sub>)<sub>3</sub>&middot;Zn<sub>4</sub>0(P0<sub>4</sub>)<sub>3</sub>: M, = 658.63, monoclinic, space group P2<sub>1</sub> (No. 4), a = 7.6569 (5) &Aring;, b = 15.241 (1)&Aring;, c= 7.6589 (5) &Aring;, {beta} = 92.740 (1)0, V= 892.7 (5) &Aring;<sup>3</sup>, Z = 2, R(F)= 8.07%, R<sub>W</sub>(F)= 9.60% (2694 reflections, 106 parameters).
Date: May 7, 1999
Creator: Chavez, Alejandra V.; Harrison, William T.A.; Nenoff, Tina M. & Phillips, Mark L.F.
Partner: UNT Libraries Government Documents Department

Tetrahedral-Network Organo-Zincophosphates: Syntheses and Structures of (N(2)C(6)H(14)).Zn(HPO(4))(2).H(2)O, H(3)N(CH(2))(3)NH(3).Zn(2)(HPO(4))(3) and (N(2)C(6)H(14)).Zn(3)(HPO(4))(4)

Description: The solution-mediated syntheses and single crystal structures of (N<sub>2</sub>C<sub>6</sub>H<sub>14</sub>)&middot;Zn(HPO<sub>4</sub>)<sub>2</sub>&middot;H<sub>2</sub>O (I), H<sub>3</sub>N(CH<sub>2</sub>)<sub>3</sub>NH<sub>3</sub>&middot;Zn<sub>2</sub>(HPO<sub>4</sub>)<sub>3</sub> (II), and (N<sub>2</sub>C<sub>6</sub>H<sub>14</sub>)&middot;Zn<sub>3</sub>(HPO<sub>4</sub>)<sub>4</sub> (III) are described. These phases contain vertex-sharing Zn0<sub>4</sub> and HP0<sub>4</sub> tetrahedra, accompanied by doubly- protonated organic cations. Despite their formal chemical relationship, as members of the series of t&middot;Zn<sub>n</sub>(HP0<sub>4</sub>)<sub>n+1</sub> (t= template, n = 1-3), these phases adopt fimdamentally different crystal structures, as one-dimensional, two-dimensional, and three-dimensional Zn0<sub>4</sub>/HP0<sub>4</sub> networks, for I, II, and III respectively. Similarities and differences to some other zinc phosphates are briefly discussed. Crystal data: (N<sub>2</sub>C<sub>6</sub>H<sub>14</sub>)&middot;Zn(HP0<sub>4</sub>)<sub>2</sub>&middot;H<sub>2</sub>0, M<sub>r</sub> = 389.54, monoclinic, space group P2<sub>1</sub>/n (No. 14), a = 9.864 (4) &Aring;, b = 8.679 (4) &Aring;, c = 15.780 (3) &Aring;, &beta; = 106.86 (2)&deg;, V= 1294.2 (8) &Aring;<sup>3</sup>, Z = 4, R(F) = 4.58%, R<sub>W</sub>(F) = 5.28% [1055 reflections with I >3&sigma;(I)]. H<sub>3</sub>N(CH<sub>2</sub>)<sub>3</sub>NH<sub>3</sub>&middot;Zn<sub>2</sub>(HP0<sub>4</sub>)<sub>3</sub>, M<sub>r</sub> = 494.84, monoclinic, space group P2<sub>1</sub>/c (No. 14), a= 8.593 (2)&Aring;, b= 9.602 (2)&Aring;, c= 17.001 (3)&Aring;, &beta;= 93.571 (8)&deg;, V = 1400.0 (5) &Aring;<sup>3</sup>, Z = 4, R(F) = 4.09%, R<sub>W</sub>(F) = 4.81% [2794 reflections with I > 3&sigma; (I)]. (N<sub>2</sub>C<sub>6</sub>H<sub>14</sub>)&middot;Zn<sub>3</sub>(HP0<sub>4</sub>)<sub>4</sub>, M<sub>r</sub>= 694.25, monoclinic, space group P2<sub>1</sub>/n (No. 14), a = 9.535 (2) &Aring;, b = 23.246 (4)&Aring;, c= 9.587 (2)&Aring;, &beta;= 117.74 (2)&deg;, V= 1880.8 (8) &Aring;<sup>3</sup>, Z = 4, R(F) = 3.23%, R<sub>W</sub>(F) = 3.89% [4255 reflections with 1> 3&sigma;(I)].
Date: May 7, 1999
Creator: Chavez, Alejandra V.; Hannooman, Lakshitha; Harrison, William T.A. & Nenoff, Tina M.
Partner: UNT Libraries Government Documents Department