scholarly journals Role of the Li+node in the Li-BH4substructure of double-cation tetrahydroborates

2014 ◽  
Vol 70 (5) ◽  
pp. 871-878 ◽  
Author(s):  
Pascal Schouwink ◽  
Ľubomír Smrčok ◽  
Radovan Černý
Keyword(s):  
Three Dimensional ◽  
Light Metal ◽  
First Principles Calculations ◽  
Eutectic Melting ◽  
One Dimensional ◽  
X Ray ◽  
Multi Phase ◽  
New Compounds ◽  
Li Content

The phase diagram LiBH4–ABH4(A= Rb,Cs) has been screened and revealed ten new compounds LiiAj(BH4)i+j(A= Rb, Cs), withi,jranging between 1 and 3, representing eight new structure types amongst homoleptic borohydrides. An approach based on synchrotron X-ray powder diffraction to solve crystal structures and solid-state first principles calculations to refine atomic positions allows characterizing multi-phase ball-milled samples. The Li-BH4substructure adopts various topologies as a function of the compound's Li content, ranging from one-dimensional isolated chains to three-dimensional networks. It is revealed that the Li+ion has potential as a surprisingly versatile cation participating in framework building with the tetrahydroborate anion BH4as a linker, if the framework is stabilized by large electropositive counter-cations. This utility can be of interest when designing novel hydridic frameworks based on alkaline metals and will be of use when exploring the structural and coordination chemistry of light-metal systems otherwise subject to eutectic melting.

Pore geometry in woven fiber structures: 0°/90° plain-weave cloth layup preform

1998 ◽  
Vol 13 (5) ◽  
pp. 1209-1217 ◽  
Author(s):  
S-B. Lee ◽  
S. R. Stock ◽  
M. D. Butts ◽  
T. L. Starr ◽  
T. M. Breunig ◽  
...  
Keyword(s):  
Gas Flow ◽  
Three Dimensional ◽  
Pore Geometry ◽  
Two Dimensional ◽  
Transverse Distribution ◽  
One Dimensional ◽  
X Ray ◽  
Woven Structures ◽  
Flow Through

Composite preform fiber architectures range from the very simple to the complex, and the extremes are typified by parallel continuous fibers and complicated three-dimensional woven structures. Subsequent processing of these preforms to produce dense composites may depend critically on the geometry of the interfiber porosity. The goal of this study is to fully characterize the structure of a 0°/90° cloth layup preform using x-ray tomographic microscopy (XTM). This characterization includes the measurement of intercloth channel widths and their variability, the transverse distribution of through-cloth holes, and the distribution of preform porosity. The structure of the intercloth porosity depends critically on the magnitude and direction of the offset between adjacent cloth layers. The structures observed include two-dimensional networks of open pipes linking adjacent holes, arrays of parallel one-dimensional pipes linking holes, and relatively closed channels exhibiting little structure, and these different structures would appear to offer very different resistances to gas flow through the preform. These measurements, and future measurements for different fiber architectures, will yield improved understanding of the role of preform structure on processing.

scholarly journals The three-dimensional structure of a class-Pi glutathione S-transferase complexed with glutathione: the active-site hydration provides insights into the reaction mechanism

1998 ◽  
Vol 333 (3) ◽  
pp. 811-816 ◽  
Author(s):  
Antonio PÁRRAGA ◽  
Isabel GARCÍA-SÁEZ ◽  
Sinead B. WALSH ◽  
Timothy J. MANTLE ◽  
Miquel COLL
Keyword(s):  
Conformational Changes ◽  
Active Site ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Glutathione S Transferase ◽  
X Ray ◽  
The Right

The structure of mouse liver glutathione S-transferase P1-1 complexed with its substrate glutathione (GSH) has been determined by X-ray diffraction analysis. No conformational changes in the glutathione moiety or in the protein, other than small adjustments of some side chains, are observed when compared with glutathione adduct complexes. Our structure confirms that the role of Tyr-7 is to stabilize the thiolate by hydrogen bonding and to position it in the right orientation. A comparison of the enzyme–GSH structure reported here with previously described structures reveals rearrangements in a well-defined network of water molecules in the active site. One of these water molecules (W0), identified in the unliganded enzyme (carboxymethylated at Cys-47), is displaced by the binding of GSH, and a further water molecule (W4) is displaced following the binding of the electrophilic substrate and the formation of the glutathione conjugate. The possibility that one of these water molecules participates in the proton abstraction from the glutathione thiol is discussed.

Electronic Structure and Hydrogen Desorption in NaAlH4

2004 ◽  
Vol 837 ◽  
Author(s):  
S. Li ◽  
P. Jena ◽  
C. M. Araujo ◽  
R. Ahuja
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Metal Hydrides ◽  
Hydrogen Desorption ◽  
Light Metal ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Design And Synthesis

ABSTRACTFirst principles calculations based on gradient corrected density functional theory are carried out to understand the electronic structure and mechanisms responsible for desorption of hydrogen from Ti doped and vacancy containing sodium-alanate (NaAlH4). The energy necessary to remove a hydrogen atom from Ti doped NaAlH4 is significantly smaller than that from pristine NaAlH4 irrespective of whether Ti substitutes the Na or the Al site. However, the presence of Na and Al vacancies is shown to play an even more important role: The removal of hydrogen associated with both Na and Al vacancies is found to be exothermic. It is suggested that this role of vacancies can be exploited in the design and synthesis of complex light metal hydrides suitable for hydrogen storage.

The role of the geoid in one-, two-, and three-dimensional network adjustments

CISM journal ◽  
1990 ◽  
Vol 44 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Michael G. Sideris
Keyword(s):  
Three Dimensional ◽  
One Dimensional ◽  
Control Networks ◽  
Deflections Of The Vertical ◽  
Dimensional Network ◽  
3D Network ◽  
Computational Procedures ◽  
The One ◽  
2D And 3D

The geoid and its horizontal derivatives, the deflections of the vertical, play an important role in the adjustment of geodetic networks. In the one-dimensional (1D) case, represented typically by networks of orthometric heights, the geoid provides the reference surface for the measurements. In the two-dimensional (2D) adjustment of horizontal control networks, the geoidal undulations N and deflections of the vertical ξ, η are needed for the reduction of the measured quantities onto the reference ellipsoid. In the three-dimensional (3D) adjustment, N and ξ, η are basically required to relate geodetic and astronomic quantities. The paper presents the major gravimetric methods currently used for predicting ξ, η and N, and briefly intercompares them in terms of accuracy, efficiency, and data required. The effects of N, ξ, η on various quantities used in the ID, 2D, and 3D network adjustments are described explicitly for each case and formulas are given for the errors introduced by either neglecting or using erroneous N, ξ, η in the computational procedures.

scholarly journals Synthesis, Structures and Electrochemical Properties of Lithium 1,3,5-Benzenetricarboxylate Complexes

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 126 ◽  
Author(s):  
Pei-Chi Cheng ◽  
Bing-Han Li ◽  
Feng-Shuen Tseng ◽  
Po-Ching Liang ◽  
Chia-Her Lin ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
Electrode Materials ◽  
Three Dimensional ◽  
Lithium Ion ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
X Ray ◽  
Crystal Transformation ◽  
Discharge Capacities

Four lithium coordination polymers, [Li3(BTC)(H2O)6] (1), [Li3(BTC)(H2O)5] (2), [Li3(BTC)(μ2-H2O)] (3), and [Li(H2BTC)(H2O)] (4) (H3BTC = 1,3,5-benzenetricarboxylatic acid), have been synthesized and characterized. All the structures have been determined using single crystal X-ray diffraction studies. Complexes 1 and 2 have two-dimensional (2-D) sheets, whereas complex 3 has three-dimensional (3-D) frameworks and complex 4 has one-dimensional (1-D) tubular chains. The crystal-to-crystal transformation was observed in 1–3 upon removal of water molecules, which accompanied the changes in structures and ligand bridging modes. Furthermore, the electrochemical properties of complexes 3 and 4 have been studied to evaluate these compounds as electrode materials in lithium ion batteries with the discharge capacities of 120 and 257 mAhg−1 in the first thirty cycles, respectively.

scholarly journals Role of Computational Methods in Going beyond X-ray Crystallography to Explore Protein Structure and Dynamics

2018 ◽  
Vol 19 (11) ◽  
pp. 3401 ◽  
Author(s):  
Ashutosh Srivastava ◽  
Tetsuro Nagai ◽  
Arpita Srivastava ◽  
Osamu Miyashita ◽  
Florence Tama
Keyword(s):  
Protein Dynamics ◽  
Computational Methods ◽  
Protein Structures ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
X Ray ◽  
X Ray Crystallography ◽  
Insight Into

Protein structural biology came a long way since the determination of the first three-dimensional structure of myoglobin about six decades ago. Across this period, X-ray crystallography was the most important experimental method for gaining atomic-resolution insight into protein structures. However, as the role of dynamics gained importance in the function of proteins, the limitations of X-ray crystallography in not being able to capture dynamics came to the forefront. Computational methods proved to be immensely successful in understanding protein dynamics in solution, and they continue to improve in terms of both the scale and the types of systems that can be studied. In this review, we briefly discuss the limitations of X-ray crystallography in studying protein dynamics, and then provide an overview of different computational methods that are instrumental in understanding the dynamics of proteins and biomacromolecular complexes.

Synthesis, Structure, and Properties of a New ErIII Iodate

2014 ◽  
Vol 67 (5) ◽  
pp. 763 ◽  
Author(s):  
Chun-Yang Pan ◽  
Hai-Deng Mai ◽  
Wu-Zhou Chen ◽  
Feng-Hua Zhao ◽  
Hong-Mei Yang
Keyword(s):  
Three Dimensional ◽  
Luminescence Spectroscopy ◽  
Supramolecular Network ◽  
Structure And Properties ◽  
Dsc Analysis ◽  
Hydrothermal Conditions ◽  
Scanning Calorimetry ◽  
One Dimensional ◽  
X Ray ◽  
Triclinic System

A new iodate Er(IO3)3·2H2O was synthesized under mild hydrothermal conditions. The structure has been confirmed by single-crystal X-ray analysis. It crystallizes in the triclinic system with space group P-1 (No.2), a = 7.338(4) Å, b = 7.506(4) Å, c = 9.409(5) Å, α = 79.698(5)°, β = 85.245(4)°, γ = 71.934(4)°, V = 484.5(5) Å3, Z = 2. Some characterizations were performed such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric–differential scanning calorimetry (TG-DSC) analysis, luminescence spectroscopy, and magnetic property measurements. The overall framework of Er(IO3)3·2H2O is based on one-dimensional chains. The adjacent chains are further linked with each other by hydrogen bonds to form a three-dimensional supramolecular network. The luminescent and magnetic properties of Er(IO3)3·2H2O were studied.

A one-dimensional coordination polymer with a three-dimensional supramolecular framework:catena-poly[[[(3,4,7,8-tetramethyl-1,10-phenanthroline)cadmium(II)]-μ3-4,4′-sulfonyldibenzoato] trihydrate]

2013 ◽  
Vol 69 (3) ◽  
pp. 241-243 ◽  
Author(s):  
Jun Wang ◽  
Jian-Qing Tao ◽  
Xiao-Juan Xu ◽  
Chun-Yun Tan
Keyword(s):  
Three Dimensional ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Polymeric Compound ◽  
Chain Polymer ◽  
One Dimensional ◽  
X Ray ◽  
Carboxylate Groups ◽  
Metal Organic ◽  
Coordination Patterns

In the title mixed-ligand metal–organic polymeric compound, {[Cd(C14H8O6S)(C16H16N2)]·3H2O}n, the asymmetric unit contains a crystallographically unique CdIIatom, one doubly deprotonated 4,4′-sulfonyldibenzoic acid (H2SDBA) ligand, one 3,4,7,8-tetramethyl-1,10-phenanthroline (TMPHEN) molecule and three solvent water molecules. Each CdIIcentre is six-coordinated by two O atoms from a chelating carboxylate group of a SDBA2−ligand, two O atoms from monodentate carboxylate groups of two different SDBA2−ligands and two N atoms from a chelating TMPHEN ligand. There are two coordination patterns for the carboxylate groups of the SDBA2−ligand, with one in a μ1-η1:η1chelating mode and the other in a μ2-η1:η1bis-monodentate mode. Single-crystal X-ray diffraction analysis revealed that the title compound is a one-dimensional double-chain polymer containing 28-membered rings based on the [Cd2(CO2)2] rhomboid subunit. More interestingly, a chair-shaped water hexamer cluster is observed in the compound.

A new three-dimensional CdIIsupramolecular framework constructed from the 1-[(1H-tetrazol-5-yl)methyl]-1,4-diazoniabicyclo[2.2.2]octane ligand

2015 ◽  
Vol 71 (2) ◽  
pp. 93-96 ◽  
Author(s):  
Qiang Li ◽  
Hui-Ting Wang ◽  
Lin Zhou
Keyword(s):  
Crystal Packing ◽  
Three Dimensional ◽  
Supramolecular Network ◽  
Stacking Interactions ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
X Ray ◽  
Distorted Octahedral Coordination Geometry ◽  
Distorted Octahedral ◽  
Cl Atoms

A new tetrazole–metal supramolecular compound, di-μ-chlorido-bis(trichlorido{1-[(1H-tetrazol-5-yl-κN2)methyl]-1,4-diazoniabicyclo[2.2.2]octane}cadmium(II)), [Cd2(C8H16N6)2Cl8], has been synthesized and structurally characterized by single-crystal X-ray diffraction. In the structure, each CdIIcation is coordinated by five Cl atoms (two bridging and three terminal) and by one N atom from the 1-[(1H-tetrazol-5-yl)methyl]-1,4-diazoniabicyclo[2.2.2]octane ligand, adopting a slightly distorted octahedral coordination geometry. The bridging bicyclo[2.2.2]octane and chloride ligands link the CdIIcations into one-dimensional ribbon-like N—H...Cl hydrogen-bonded chains along thebaxis. An extensive hydrogen-bonding network formed by N—H...Cl and C—H...Cl hydrogen bonds, and interchain π–π stacking interactions between adjacent tetrazole rings, consolidate the crystal packing, linking the poymeric chains into a three-dimensional supramolecular network.

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