7.1.3.1 Crystal structures. Lattice parameters

2005 ◽  
pp. 84-87
Author(s):  
E. Burzo
Keyword(s):  
Crystal Structures ◽  
Lattice Parameters

Zur Struktur und Dotierung von Selenosilikaten: die Kristallstruktur von Er2SeSiO4 und Er3,75Ca0,25Se2,75Cl0,25Si2O7 Structure and Doping of Seleno Silicates: the Crystal Structures of Er2SeSiO4 and Er3,75Ca0,25Se2,75Cl0,25Si2O7

1994 ◽  
Vol 49 (6) ◽  
pp. 733-740 ◽  
Author(s):  
Klaus Stöwe
Keyword(s):  
Crystal Structures ◽  
Structure Analysis ◽  
Rare Earths ◽  
Structure Determination ◽  
Lattice Parameters ◽  
Energy Dispersive ◽  
Space Group ◽  
X Ray ◽  
By Products

Well-shaped brown and pink isometric crystals were obtained as by-products of the synthesis of erbium selenides from the elements in evacuated and sealed silica ampoules with graphite inlets. They could be identified as erbium seleno mono- and disilicates by energy dispersive X-ray fluorescence and X-ray structure determination. The monosilicate Er2SeSiO4 crystallizes isotypically to Nd2SeSiO4 in the space group Pbcm with the lattice parameters a = 600.2(2), b = 688.0(2), c = 1075.2(2) pm and represents the second known seleno inosilicate of the rare earths. From X-ray structure analysis an isotypic relation between the disilicate Er3,75Ca0,25Se2,75Cl0,25Si2O7 and the compound Sm4S3Si2O7 was found, the former crystallizing in the space group I41/amd with the lattice parameters a - 1177.7(2) and c = 1376.5(2) pm. The doping o f the sorosilicate with the elements Ca and Cl originated from contam inations in the graphit inlets used in the procedure

scholarly journals FIDEL: A new method for SDPD of nanocrystalline organic compounds

2014 ◽  
Vol 70 (a1) ◽  
pp. C134-C134
Author(s):  
Martin Schmidt ◽  
Stefan Habermehl ◽  
Philipp Moerschel ◽  
Pierre Eisenbrandt
Keyword(s):  
Crystal Structures ◽  
Rietveld Refinement ◽  
Organic Compounds ◽  
Structure Data ◽  
Structural Model ◽  
Lattice Energy ◽  
Lattice Parameters ◽  
Low Energy ◽  
Powder Pattern ◽  
Field Methods

Rietveld refinements generally fail, if the lattice parameters of the structural model differ more than slightly from the correct lattice parameters and the simulated reflections do not overlap with the experimental ones. For molecular crystals, we have developed a more robust fitting algorithm, which uses the cross-correlation function of calculated and experimental powder patterns, and allows a FIt with DEviating Lattice parameters (FIDEL). The method is also successful for nanocrystalline organic compounds showing only 10-20 peaks in their powder diagrams. The FIDEL method has proven to be useful for various applications, including refinements starting from (1) structure data of an isostructural chemical derivative; (2) structure data of an isostructural hydrate or solvate; (3) structure data from measurements at another temperature (e.g. for fitting a room-temperature powder diagram starting with a structure determined from a single-crystal measurement at 100K). FIDEL is also used for determining crystal structures from non-indexed powder diagrams of nanocrystalline organic compounds. Three steps are performed: (1) Prediction of possible crystal structures in various space groups using global lattice-energy minimizations by force-field methods. (2) FIDEL fit of 100 to 600 low-energy structures to the experimental powder pattern. The structure candidate leading to the correct structure results in a significantly better fit than all other structures. (3) Rietveld refinement. The FIDEL method was used to determine the hitherto unknown crystal structure of the nanocrystalline alpha-phase of 2,9-dichloroquinacridone (C20H10Cl2N2O2). The upper part of the figure shows the experimental powder pattern and the simulated powder diagram of one of the predicted low-energy structures before any fitting. The lower part displays the result of the FIDEL fit, before the Rietveld refinement.

Microstructures of Bi-based oxide superconductors doped with Sb

1992 ◽  
Vol 7 (10) ◽  
pp. 2667-2672 ◽  
Author(s):  
Yoshio Masuda ◽  
Rikuro Ogawa ◽  
Yoshio Kawate ◽  
Naohiro Hara ◽  
Tsuyoshi Tateishi
Keyword(s):  
Activation Energy ◽  
Time Dependence ◽  
Crystal Structures ◽  
Sol Gel ◽  
Lattice Parameters ◽  
Oxide Superconductors ◽  
Arrhenius Plots ◽  
Gel Method ◽  
Superconducting Phases ◽  
Xrd Method

Using Bi-based oxide superconductors of the Bi0.96Pb0.24-xSbxSr1.0Ca 1.1 Cu1.6Oy composition which were prepared by the sol-gel method, production of the high-Tc phase and also microstructures of the high-Tc and the low-Tc phases were investigated using the XRD method and the TEM technique. Two superconducting phases showed good linearities of shrinkages of the a, b, and c lattice parameters as the Sb content increased, and so it has been found that Sb can be included in superconducting crystal structures. However, all shrinkages were below 1%. The activation energy of Sb diffusion was estimated from time dependence of changes of the lattice parameters using the Arrhenius plots. Its energy was from 510 to 593 Kj/mol.

New Thiostannates Synthesized Under Solvothermal Conditions: Crystal Structures of (trenH)2Sn3S7 and {[Mn(tren)]2Sn2S6}

2012 ◽  
Vol 67 (10) ◽  
pp. 1098-1106 ◽  
Author(s):  
Nicole Pienack ◽  
Diana Schinkel ◽  
Angela Puls ◽  
Marie-Eve Ordolff ◽  
Henning Lühmann ◽  
...  
Keyword(s):  
Band Gap ◽  
Crystal Structures ◽  
Bond Formation ◽  
Lattice Parameters ◽  
Triclinic Space Group ◽  
Space Group ◽  
Trigonal Bipyramidal ◽  
Solvothermal Conditions

The two new thiostannate compounds (trenH)2Sn3S7 (1) and {[Mn(tren)]2Sn2S6} (2) (tren=tris-2-aminoethylamine) were obtained under solvothermal conditions. Compound 1 crystallizes in the hexagonal space group P63/mmc with a=13.2642(19), c=19.078(3) Å, V =2906.9(7) Å3. The layered [Sn3S7]2- anion is constructed by Sn3S4 semi-cubes sharing common edges. The layers are characterized by large hexagonal pores with dimensions of about 11×11 Å2. Compound 2 crystallizes in the triclinic space group P1̄ with lattice parameters a=7.6485(7), b=8.1062(7), c=12.1805(11) Å, α =97.367(11), β =103.995(11), γ = 108:762(10)°, V =676.17(10) Å3. The [Sn2S6]4- anion is composed of two edge-sharing SnS4 tetrahedra and joins two Mn2+-centered complexes by Mn-S bond formation. The Mn2+ cation is in a trigonal-bipyramidal environment of four N atoms of the tren ligand and one S atom of the thiostannate anion. Both compounds are semiconductors with a band gap of 2:96 eV for 1 and of 2:75 eV for 2.

New insight into the crystal structure of orthorhombic edingtonite: evidence for a split Ba site

2004 ◽  
Vol 68 (1) ◽  
pp. 167-175 ◽  
Author(s):  
G. D. Gatta ◽  
T. Boffa Ballaran
Keyword(s):  
Crystal Structure ◽  
British Columbia ◽  
Crystal Structures ◽  
Lattice Parameters ◽  
Space Group ◽  
Physicochemical Conditions ◽  
Report Data ◽  
First Time ◽  
Insight Into

AbstractOrthorhombic edingtonite has been found coexisting with tetragonal edingtonite in a specimen from Ice River, British Columbia, Canada.We report data on the composition and crystal structure of the orthorhombic sample. Lattice parameters are: a = 9.5341(6), b = 9.6446(6), c = 6.5108(7)Å, V = 598.68(8)Å 3. The crystal structure was refined in space group P 21212 to R1 = 1.8% using 879 observed reflections. For the first time, evidence for splitting of the extra-framework Ba site in two different sites (Ba1, Ba2), ~0.37 Å apart, is demonstrated. A comparison with the published crystal structures of tetragonal and orthorhombic edingtonite is made.The present result supports the suggestion that the two edingtonite phases are a consequence of different nucleation phenomena and not different physicochemical conditions.

Nanoscopic unequivocal analysis of twinned crystal structures with tetragonal or orthogonal unit cells by electron microdiffraction

1999 ◽  
Vol 32 (3) ◽  
pp. 397-403 ◽  
Author(s):  
M. Leicht ◽  
T. Remmele ◽  
D. Stenkamp ◽  
H. P. Strunk
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Lattice Parameters ◽  
Transmission Electron ◽  
Unit Cells ◽  
Convergent Beam ◽  
Chalcogenide Compound ◽  
Habit Planes ◽  
Twinned Crystal Structure ◽  
Electron Microdiffraction

In this study, a particular type of nanoscopic twinned crystal structure which can occur in any tetragonal or orthogonal crystal structure with a ratio of lattice parameters c/a=c/b=2 is presented. This type of twinning is characterized by twin components whosecaxes are oriented perpendicular to one another, by twin-habit planes parallel to {102} planes, and by a superstructure along the twin boundaries which is described by orthogonal unit cells with lattice parameters 2a, 2a,a. Furthermore, the suitability of electron microdiffraction, a diffraction technique of transmission electron microscopy (TEM) with a moderately convergent beam, for the analysis of such twinned crystal structures is demonstrated. For this demonstration, electron microdiffraction is applied to the chalcogenide compound Cu2In3Se5, which indeed exhibits the proposed twinned crystal structure.

Zur Kenntnis der Tief-und Hochtemperaturform eines Oxidarsenats des Zinks: ZnOZn3(AsO4)2

1996 ◽  
Vol 51 (2) ◽  
pp. 233-239 ◽  
Author(s):  
D. Frerichs ◽  
C.H. Park ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Single Crystals ◽  
Crystal Structures ◽  
Lattice Parameters ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Temperature Form ◽  
Laser Techniques ◽  
Similarities And Differences

Abstract Single crystals of the low (t-) and high (h-) temperature form of ZnOZn3(AsO4)2 have been prepared by flux and by CO2-LASER techniques respectively. Both compounds crystal­lizes monoclinic, space group C52h-P21/n with the lattice parameters t-ZnOZn3(AsO4)2: a = 9.807(3), b = 8.180(2), c = 9.967(2) Å , β = 116.53(2)°, Z = 4 and h -ZnOZn3(AsO4)2: a = 9.743(3), b = 8.163(8), c = 17.933(2) Å , β = 91.55(2)°, Z = 8. Similarities and differences of the crystal structures will be discussed.

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