scholarly journals The Crystal Structure and Chemical Properties of U2Al3C4 and Structure Refinement of Al4C3

1995 ◽  
Vol 50 (2) ◽  
pp. 196-200 ◽  
Author(s):  
Thorsten M. Gesing ◽  
Wolfgang Jeitschko
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Refinement ◽  
Chemical Properties ◽  
Variable Parameters ◽  
Higher Symmetry ◽  
Structure Factors ◽  
Hydrolysis Of ◽  
Symmetry Space ◽  
Symmetry Space Group

A well crystallized sample of U2Al3C4 was obtained by melting the elemental components in a carbon crucible in a high frequency furnace. The crystal structure of this compound was determined from single-crystal diffractometer data of a twinned crystal: P63mc, a = 342.2(1) pm. c = 2323.0(3) pm. Z = 2 , R = 0.030 for 537 structure factors and 18 variable parameters. The structure can also be described in the higher symmetry space group P63/mmc with one split aluminum position. It consists of close packed layers of uranium and aluminum atoms with carbon atoms at interstitial sites. The structure is closely related to that of Al4C3, which was refined from single-crystal X-ray data to a residual of R = 0.033 for 135 F-values and 11 variables. The hydrolysis of U2Al3C4 with diluted hydrochloric acid resulted in about 74 (wt-)% methane, 8% ethane and ethylene, and 18% saturated and unsaturated higher hydrocarbons.

Preparation and Crystal Structures of Ternary Rare Earth Silver and Gold Arsenides LnAgAs2 and LnAuAs2 with Ln = La–Nd, Sm, Gd, and Tb

2003 ◽  
Vol 58 (5) ◽  
pp. 399-409 ◽  
Author(s):  
Marcus Eschen ◽  
Wolfgang Jeitschko
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Refinement ◽  
Gold Compound ◽  
Crystal Structure Refinement ◽  
Variable Parameters ◽  
Structure Factors ◽  
Formal Charge ◽  
Gold Compounds ◽  
Silver Compounds

The 14 arsenides LnAgAs2 and LnAuAs2 (Ln = La-Nd, Sm, Gd, Tb) were prepared by reaction of stoichiometric mixtures of the elemental components at high temperatures and characterized by Xray diffractometry. The silver compounds LaAgAs2 and CeAgAs2 and the gold compounds LnAuAs2 (Ln = Ce-Nd, Sm, Gd, Tb) crystallize with HfCuSi2 type structure (P4/nmm, Z = 2). Of these, the structures of CeAgAs2 (a = 408.5(1), c = 1048.2(1) pm, conventional residual R = 0.017 for 261 structure factors and 12 variable parameters) and CeAuAs2 (a = 411.4(1), c = 1015.3(2) pm, R = 0.030 for 428 F values) were refined from four-circle diffractometer data. The silver compounds LnAgAs2 (Ln = Pr, Nd, Sm, Gd, Tb) are isotypic with the antimonide SrZnSb2 (Pnma, Z = 4) as demonstrated by a single-crystal structure refinement of PrAgAs2 (a = 2107.3(4), b = 401.7(1), c = 407.8(1) pm, R = 0.042 for 746 F values and 26 variables). The gold compound LaAuAs2 (I4/mmm, Z = 4, a = 416.9(1), c = 2059.5(3) pm, R = 0.038 for 303 F values and 13 variables) was found to be isotypic with the bismuthide SrZnBi2, again by a refinement from single-crystal diffractometer data. In the structures of CeAgAs2, LaAuAs2, and CeAuAs2 large displacement parameters perpendicular to the four-fold axes were found for one of the two arsenic positions. These structures could also be refined with split positions for these arsenic atoms, which allow for considerable As-As bonding, resulting in a formal charge of −1 for these atoms. Chemical bonding in these compounds can thus be rationalized by a simple model corresponding to the formula Ln+3T+1As−1As−3 (T = Ag, Au), where the superscripts indicate oxidation numbers.

The Crystal Structure of the Potential Ferroelectric Calcium Rhenate(VI, VII) Ca11Re4O24 and its Relation to the Structure of Sr11Os4O24

1998 ◽  
Vol 53 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Wolfgang Jeitschko ◽  
Horst A. Mons ◽  
Ute Ch. Rodewald ◽  
Manfred H. Möller
Keyword(s):  
Variable Parameters ◽  
Higher Symmetry ◽  
Space Group ◽  
X Ray ◽  
Coordination Numbers ◽  
Structure Factors ◽  
The Common ◽  
The Difference ◽  
Symmetry Space ◽  
Symmetry Space Group

The title compound was prepared in well-crystallized form by thermal decomposition of Ca5Re2O12. Its structure was determined from single-crystal X-ray diffractometer data: I41, a = 1107.0(1), c = 1609.3(1) pm, Z = 4, R = 0.056 for 4565 structure factors and 119 variable parameters. The calcium atoms occupy seven different sites with 8, 9, or 10 oxygen neighbors. The two different rhenium atoms are octahedrally coordinated by oxygen atoms with average Re-O distances of 193.1 and 187.7 pm for the six- and seven-valent rhenium atoms, respectively. The compound shows Curie-Weiss behavior with a magnetic moment of μexp = 1.15(±0.10) μB per Re(VI) atom. The structure is closely related to that of Sr11Os4O24 which, however, crystallizes in the space group I2/a. The difference between the two structures arises through the higher coordination numbers of the strontium atoms. It is suggested that at high temperature both compounds crystallize in the common higher symmetry space group I4/a. Since Ca11Re4O24 crystallizes in the pyroelectric class 4 this compound is expected to be ferroelectric.

scholarly journals N′-[(E)-4-Bromobenzylidene]-2-(4-isobutylphenyl)propanohydrazide

2009 ◽  
Vol 65 (6) ◽  
pp. o1184-o1185 ◽  
Author(s):  
Hoong-Kun Fun ◽  
Ching Kheng Quah ◽  
K. V. Sujith ◽  
B. Kalluraya
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Asymmetric Unit ◽  
Higher Symmetry ◽  
Space Group ◽  
Compound C ◽  
Benzene Rings ◽  
Independent Molecules ◽  
Symmetry Space ◽  
Symmetry Space Group

The asymmetric unit of the title compound, C20H23BrN2O, contains two independent molecules (AandB), in which the orientations of the 4-isobutylphenyl units are different. The dihedral angle between the two benzene rings is 88.45 (8)° in moleculeAand 89.87 (8)° in moleculeB. MoleculesAandBare linked by a C—H...N hydrogen bond. In the crystal, molecules are linked into chains running along theaaxis by intermolcular N—H...O and C—H...O hydrogen bonds. The crystal structure is further stabilized by C—H...π interactions. The presence of pseudosymmetry in the structure suggests the higher symmetry space groupPbca. However, attempts to refine the structure in this space group resulted in a disorder model with highR(0.097) andwR(0.257) values. The crystal studied was an inversion twin with a 0.595 (4):0.405 (4) domain ratio.

Strukturchemische Untersuchungen an Scandium-Cobalt-Phosphiden mit einem Metall:Phosphor-Verhältnis von 2:1

1985 ◽  
Vol 40 (7) ◽  
pp. 900-905 ◽  
Author(s):  
Wolfgang Jeitschko ◽  
Elke J. Reinbold
Keyword(s):  
Coordination Polyhedra ◽  
Variable Parameters ◽  
Lattice Constants ◽  
Orthorhombic Lattice ◽  
Metal Atoms ◽  
Structure Factors ◽  
New Type ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
Counter Data

Abstract Several new scandium cobalt phosphides were prepared by reaction of the elemental components in a tin flux. ScCoP has a TiNiSi-type structure with the orthorhombic lattice constants a = 6.268(2) Å , b = 3.750(1) Å , c = 7.050(3) Å. ScCo5P3 is isotypic with YCo5P3. Its orthorhombic lattice constants are: a = 11.691(5) Å , b = 3.583(1) Å , c = 10.206(3) Å. Sc2Co12P7crystallizes with the hexagonal Zr2Fe12P7 structure with a = 8.973(3) Å, c = 3.531(1) Å. Sc5Co19P12 is of a new type which is closely related to the structure of Hf2Co4P3. It has hexagonal symmetry, space group P6̄2m -D3h3 and the lattice constants a - 12.124(7) Å , c = 3.633(2) Å , with Z = 1 formula unit per cell. The structure was determined and refined with isotropic thermal parameters from single-crystal counter data to a residual of R = 0.023 for 848 unique structure factors and 24 variable parameters. Considering the environments of the phosphorus atoms the structures are all closely related. There are, however, considerable differences in the coordination polyhedra of the metal atoms.

Zur Kenntnis des Kupfer-Oxid-Arsenats Cu4O(A sO4)2 / On the Copper Oxide Arsenate Cu4O(AsO4)2

1996 ◽  
Vol 51 (9) ◽  
pp. 1279-1282 ◽  
Author(s):  
M. Staack ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Crystal Structure ◽  
Copper Oxide ◽  
Single Crystal ◽  
Copper Ions ◽  
Space Group ◽  
X Ray ◽  
Different Types ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
Anionic Part

The copper oxide arsenate Cu4O(AsO4)2 has been prepared and investigated by single crystal X-ray techniques. The compound crystallizes with triclinic symmetry, space group C1i-P1̄, a = 6.4148(7), b = 7.6549(5), c = 8.2241(7) Å, α = 98.52(1), β = 112.39(1), 7 = 98.38(1)°, Z = 2. Cu4O(AsO4)2 is isotypic to Cu4(PO4)2O . Copper ions on one of the four specified sites show nearly planar coordination by O2- and may be assigned to the anionic part of the crystal structure. One of the nine different types of oxygen atoms is coordinated by copper exclusively. The compound is therefore classified as an oxide arsenate.

The Silver(I) Mercury(II) Oxide Nitrate with the Empirical Formula AgHg2NO5

1999 ◽  
Vol 54 (12) ◽  
pp. 1489-1494 ◽  
Author(s):  
Thomas J. Mormann ◽  
Wolfgang Jeitschko
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Single Crystal ◽  
Solid State Reaction ◽  
Title Compound ◽  
Empirical Formula ◽  
Variable Parameters ◽  
Structure Factors ◽  
Linear Coordination ◽  
Oxygen Atoms

The title compound was prepared by solid state reaction of Ag2O with Hg(NO3)2· H2O in air at 350 °C. Its crystal structure was determined from single-crystal diffractometer data: Pnma, a = 620.1(1) pm, b = 670.1(1) pm, c = 1267.5(2) pm, Z = 4, R = 0.026 for 586 structure factors and 33 variable parameters. The compound may be represented by the formula Ag(HgO)2NO3 . The mercury(II) together with the oxygen atoms form zig-zag chains with linear coordination of the mercury atoms. The oxygen atoms of these chains are linked via silver(I) atoms, thus forming two-dimensionally infinite nets, which contain the trigonal planar nitrate groups in interstices. Thus, only secondary Hg-O and Ag-O bond are formed between the nets.

Trabzonite, Ca4[Si3O9(OH)]OH: crystal structure, revised formula, new occurrence and relation to killalaite

2012 ◽  
Vol 76 (3) ◽  
pp. 455-472 ◽  
Author(s):  
T. Armbruster ◽  
B. Lazic ◽  
I. O. Galuskina ◽  
E. V. Galuskin ◽  
E. Gnos ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Refinement ◽  
Northern Caucasus ◽  
Orthorhombic Symmetry ◽  
X Ray ◽  
Degree Of Condensation ◽  
Modular Structures ◽  
Symmetry Space ◽  
Monoclinic Cell

AbstractThe crystal structure of the rare skarn mineral trabzonite, Ca4[Si3O9(OH)]OH, from the type locality near Ikizdere, Turkey and from the Upper Chegem caldera, Northern Caucasus, Kabardino-Balkaria, Russia has been solved and refined using single-crystal X-ray data. This shows that the chemical formula should be modified from Ca4(Si3O10)˙2H2O, reported in the original trabzonite description, to an OH-bearing composition. The crystal structure, which contains Si3O10 trimers embedded in a framework of CaO6–8 polyhedra, has orthorhombic symmetry, space group Ama2, a = 20.6, b = 9.1, c = 10.3 Å. The orthorhombic A-centred cell is easily obtained by transformation from the original monoclinic cell of P21/m symmetry. The revised formula means that trabzonite and foshagite are polymorphs; foshagite has wollastonite-like silicate chains and in contrast to trabzonite it does not contain silanol groups. The structure and composition of killalaite from both localities was also studied. Single-crystal X-ray structure refinement of killalaite from the Northern Caucasus confirmed it to be non-stoichiometric with a composition between Ca6[Si2O6(OH)]2(OH)2 and Ca7[Si2O7]2(OH)2(Z = 2). Trabzonite, killalaite and dellaite form a series of modular structures which differ mainly in the degree of condensation of the SiO4 units.

scholarly journals Preparation and Crystal Structure of the Carbides Ln12Re5C15 (Ln = Y, La-N d, Gd-Er)

1994 ◽  
Vol 49 (8) ◽  
pp. 1081-1088 ◽  
Author(s):  
Rainer Pöttgen ◽  
Günter Block ◽  
Wolfgang Jeitschko ◽  
Ronald K. Behrens
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Formula Unit ◽  
Variable Parameters ◽  
X Ray ◽  
Arc Melting ◽  
Structure Factors

The title compounds were prepared by arc-melting of the elemental components and sub­sequent annealing. Their crystal structure is hexagonal P 6̅ 2 m with one formula unit per cell. It was determined from single-crystal X-ray data of La12Re5C15 (a =1116.8(1) pm, c =545.3(1) pm, R = 0.060 for 287 structure factors and 27 variable parameters) and Ho12Re5C15 (ia = 1066.7(1) pm, c = 504.2(1) pm, R = 0.018 for 392 F's and 31 variables). The structures correspond to the formula Ln12[ReC3]2[Re3C3(C2)3],where the brackets indicate two differ­ent trigonal planar anionic rhenium-carbon groups. The coordination of the rhenium atoms in these polyanions seems to be compatible with the 18-electron rule.

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