Structure Determination of Ho2PdSi3

Holmium-Palladium-Silicide Ho2PdSi3 is a member of rare earth-transition metal silicides exhibiting a wide range of interesting magnetic and electrical properties like multiple transition temperatues. The crystal structure results from HoSi2 by substitution of Si by Pd which is ordering commensurably with a 2 × 2 × 8 superstructure confirmed by a previous XRD and a Diffraction Anomalous Fine Structure (DAFS) measurement of the super structure reflection 1/2 1/2 3/8. DAFS is a X-ray method combining the advantages of absorption and diffraction and hence offers the possibility of element and site selective studies. Thus, it was feasible to probe the local environment of Ho and Pd separately. In the following, we will present a comparison of several structure proposals of Ho2PdSi3 with experimental data from beamline E2 and BW1 of the former synchrotron DORIS III at DESY/HASYLAB.

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EVALUATION OF THE STRESSED DEFORMED STATE OF MAIN GAS PIPELINES RUNNING IN PERMANENTLY FROZEN GROUNDS

Kontrol Diagnostika ◽

10.14489/td.2020.12.pp.058-063 ◽

2020 ◽

pp. 58-63

Author(s):

M. M. Sidorov ◽

N. I. Golikov ◽

R. P. Tihonov

Keyword(s):

Experimental Data ◽

Calculated Data ◽

Gas Pipeline ◽

Loss Of Stability ◽

Portable Equipment ◽

Ray Method ◽

X Ray ◽

Deformed State ◽

Pipeline Monitoring

The work evaluates the stress deformed state of the section of the interfield gas collecting main, running in permanently frozen grounds. The object of research is a section of a pipeline with an arched discharge formed as a result of loss of stability as a result of thermal erosion of permanently frozen grounds to disturbance of the vegetation cover. The determination of stresses was carried out by the X-ray method using portable equipment. The experimental data were analyzed with the calculated. The calculated data were obtained by measuring the spatial position of the gas pipeline section. The obtained values of the acting stresses and the estimates of the critical indicators of the gas pipeline monitoring section made it possible to reasonably estimate the stress state. The methodology for determining the acting stresses of pipelines using portable X-ray equipment can be successfully applied to estimate the stressed-deformed state of pipeline systems running in the zone of permafrost.

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Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

10.26434/chemrxiv.11345063.v2 ◽

2020 ◽

Author(s):

Keishiro Yamashita ◽

Kazuki Komatsu ◽

Hiroyuki Kagi

Keyword(s):

Crystal Structure ◽

High Pressure ◽

Crystal Growth ◽

Single Crystal ◽

Room Temperature ◽

Growth Technique ◽

Salt Hydrate ◽

X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

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The protonation of the ethylenediphosphinetetraacetate anion and the crystal structure of the bis (hydrogen bromide) of ethylenediphosphinetetraacetic acid

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19813063 ◽

1981 ◽

Vol 46 (12) ◽

pp. 3063-3073 ◽

Cited By ~ 5

Author(s):

Jana Podlahová ◽

Bohumil Kratochvíl ◽

Vratislav Langer ◽

Josef Šilha ◽

Jaroslav Podlaha

Keyword(s):

Crystal Structure ◽

Hydrogen Bonds ◽

Structure Determination ◽

Free Acid ◽

Hydrogen Bromide ◽

Carboxyl Groups ◽

Spectroscopic Methods ◽

X Ray ◽

Partial Formation

The equilibria and mechanism of addition of protons to the ethylenediphosphinetetraacetate anion (L4-) were studied in solution by the UV, IR, 1H and 31P NMR spectroscopic methods. A total of six protons can be bonded to the anion. They are added stepwise, first with partial formation of zwitterions containing P-H bonds, which then dissociate with formation of the free acid, H4L, where all four protons are bonded in carboxyl groups. The formation of zwitterions is strongly dependent on the concentration. In the final stage, the acid bonds two additional protons to form the bis-phosphonium cation, H6L2+. A number of isostructural salts containing this cation, H4L.2 HX (X = Cl, Br, I), have been prepared. The X-ray crystal structure determination of the bromide confirmed the expected arrangement. The bromide crystals are monoclinic, a = 578.2, b = 1 425.0, c = 1 046.7 pm, β = 103.07° with a space group of P21/c, Z = 2. The final R factor was 0.059 based on 1 109 observed reflections. The structure consists of H6L2+ cations containing protons bonded to phosphorus atoms (P-H distance 134 pm) and of bromide anions, located in gaps which are also sufficiently large for I- anions in the isostructural iodide. The interbonding of phosphonium cations proceeds through hydrogen bonds, C-OH...O=C, in which the O...O distance is 275.3 pm.

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Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

Canadian Journal of Chemistry ◽

10.1139/v85-198 ◽

1985 ◽

Vol 63 (6) ◽

pp. 1166-1169 ◽

Cited By ~ 4

Author(s):

John F. Richardson ◽

Ted S. Sorensen

Keyword(s):

Crystal Structure ◽

Direct Methods ◽

Chair Conformation ◽

Molecular Structures ◽

Boat Conformation ◽

X Ray Diffraction ◽

Space Group ◽

X Ray ◽

Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

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Preparative-scale HPLC Resolution of Metallacyclic η3-Allyltricarbonyliron Complexes and Determination of the Absolute Configuration by X-Ray Crystal Structure Analysis

Journal of Chemical Research ◽

10.1177/174751989902300930 ◽

1999 ◽

Vol 23 (9) ◽

pp. 578-579

Author(s):

Rainer Schobert ◽

Hermann Pfab ◽

Jutta Böhmer ◽

Frank Hampel ◽

Andreas Werner

Keyword(s):

Crystal Structure ◽

Silica Gel ◽

Structure Analysis ◽

Absolute Configuration ◽

Crystal Structure Analysis ◽

Preparative Scale ◽

X Ray ◽

The Absolute

Racemates of (η3-allyl)tricarbonyliron lactone complex Fe(CO)3{η1:η3-C(O)XCH2CHCMeCH2} 1a (X = O) and (η3-allyl)tricarbonyliron lactam complex 2a (X = NMe) are resolved on a preparative scale by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate/silica gel RP-8 and the absolute configuration of (-)-2a is determined by X-ray crystal structure analysis.

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ChemInform Abstract: Spectroscopic Studies and X-Ray Crystal Structure Determination of the Complex cis-(S-Ethylcysteine)platinum(II)dichloride.

Chemischer Informationsdienst ◽

10.1002/chin.198238072 ◽

1982 ◽

Vol 13 (38) ◽

Author(s):

V. THEODOROU ◽

I. PHOTAKI ◽

N. HADJILIADIS ◽

R. W. GELLERT ◽

R. BAU

Keyword(s):

Crystal Structure ◽

Structure Determination ◽

Spectroscopic Studies ◽

Crystal Structure Determination ◽

X Ray

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Global X-Ray Method for the Determination of Stress Profiles

Materials Science Forum ◽

10.4028/www.scientific.net/msf.404-407.19 ◽

2002 ◽

Vol 404-407 ◽

pp. 19-24 ◽

Cited By ~ 4

Author(s):

Jean Michel Sprauel ◽

H. Michaud

Keyword(s):

Ray Method ◽

X Ray ◽

Stress Profiles

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Theoretical determination of the structures of CaSiO3 perovskites

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768106035762 ◽

2006 ◽

Vol 62 (6) ◽

pp. 1025-1030 ◽

Cited By ~ 15

Author(s):

Razvan Caracas ◽

Renata M. Wentzcovitch

Keyword(s):

Crystal Structure ◽

Experimental Data ◽

Density Functional Theory ◽

Density Functional ◽

Theoretical Determination ◽

Functional Theory ◽

Starting Point ◽

Atomic Coordinates ◽

The Ideal

Density functional theory is used to determine the possible crystal structure of the CaSiO3 perovskites and their evolution under pressure. The ideal cubic perovskite is considered as a starting point for studying several possible lower-symmetry distorted structures. The theoretical lattice parameters and the atomic coordinates for all the structures are determined, and the results are discussed with respect to experimental data.

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