Mg5Pd10Si16 und Mg5Pt10Si16, Magnesium-Platinmetall-Silicide mit Tetraedern und gekappten Tetraedern aus Silicium-Atomen / Mg5Pd10Si16 and Mg5Pt10Si16, Magnesium Platinum Metal Silicides with Si4 Tetrahedra and Si12 Truncated Tetrahedra

2002 ◽  
Vol 57 (12) ◽  
pp. 1346-1352 ◽  
Author(s):  
Peter Lorenz ◽  
Walter Jung
Keyword(s):  
Boron Nitride ◽  
Single Crystal ◽  
Crystal Structures ◽  
Three Dimensional ◽  
Platinum Metal ◽  
Close Packing ◽  
Unit Cell ◽  
Crystal Data ◽  
Lattice Constants ◽  
Metal Silicides

The ternary silicides Mg5Pd10Si16 and Mg5Pt10Si16 have been prepared by reaction of magnesium with the binary platinum-metal silicides in sealed tantalum containers (Pt-compound: 1200°C, 3 d, up 20 °/h, down 5 °/h; Pd-compound: 1000°C, 2 d, up and down 50 °/h). In the case of the Pd-compound contact with the tantalum had to be avoided by using a boron nitride crucible. The isotypic compounds crystallize in the cubic space group F4̄3m with 4 formula units per unit cell. The crystal structures were determined from single crystal data, lattice constants from Guinier patterns. The following data were obtained: a = 1258.81(8) pm for Mg5Pd10Si16 and a = 1256.94(9) pm for Mg5Pt10Si16. Short distances in the three-dimensional platinum-metal silicon network indicate strong, covalent Pd(Pt)-Si-bonding (d(Pd-Si) = 240.2 to 256.1 pm; d(Pt-Si) = 237.1 to 258.5 pm). In addition, homonuclear bonding seems to be important, resulting in the formation of Si4-tetrahedra (d(Si-Si) = 250.4 pm (Mg5Pd10Si16) and 255 pm (Mg5Pt10Si16)), empty Si12-polyhedra with the shape of truncated tetrahedra (d(Si- Si): 234.5 and 248.2 pm (Mg5Pd10Si16); 236 and 248.2 pm (Mg5Pt10Si16)), and Mg-centered Pd(Pt)10-clusters with the shape of adamantane (d(Pd-Pd) = 282.3 pm; d(Pt-Pt) = 284.5 pm). Furthermore, Mg4-tetrahedra with Mg-Mg-distances of 360 pm are formed. The structure may be described by an expanded cubic “close” packing of MgPd(Pt)10-units in which the Si4-tetrahedra occupy the octahedral holes while the Si12-polyhedra and the Mg4-tetrahedra reside in one half of the tetrahedral holes each.

Synthèse et caractérisation structurale d'un phosphate d'indium In3P2O8 présentant des paires In–In

1996 ◽  
Vol 52 (6) ◽  
pp. 905-908 ◽  
Author(s):  
V. Peltier ◽  
P. L'Haridon ◽  
R. Marchand ◽  
Y. Laurent
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Three Dimensional ◽  
Thermal Reduction ◽  
Unit Cell ◽  
Crystal Data ◽  
Space Group

The crystal structure of the new indium phosphate In3P2O8 has been determined from single-crystal data. The unit cell is cubic [space group I{\bar 4}3d (Z = 8)] with a = 11.152 (1) Å. The structure is characterized by a three-dimensional arrangement of isolated PO4 3− tetrahedra forming the anionic network, while the electroneutrality is insured by (In—In)4+ cationic pairs. The In—In distance, equal to 2.630 (1) Å, is the shortest In—In bond ever found. Powdered In3P2O8 can be synthesized from a mixture of 4 InPO4:1 In2O3 after thermal reduction under H2.

Notizen: Refinement of the Crystal Structures of CuTe2Br and CuTe2I

1989 ◽  
Vol 44 (8) ◽  
pp. 990-992 ◽  
Author(s):  
Wolfgang Milius
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Unit Cell ◽  
Lattice Parameters ◽  
Crystal Data ◽  
Space Group ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The crystal structures of CuTe2Br and CuTe2I have been refined on the basis of single crystal data. Both compounds crystallize monoclinically in space group P21/c. The structures are isotypic with that of CuTe2Cl. The lattice parameters of CuTe2Br are a = 834.5(8) pm, b = 492.8(4) pm, c = 1573.3(5) pm and β = 135.3(2)°. The unit cell dimensions of CuTe2I are a = 866.5(8) pm, b = 491.4(4) pm, c = 1649.6(3) pm and β = 135.1(2)°.

scholarly journals Intermetallic REPtZn Compounds with TiNiSi-type Structure

2011 ◽  
Vol 66 (7) ◽  
pp. 671-676 ◽  
Author(s):  
Trinath Mishra ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Coordination Number ◽  
High Frequency ◽  
Three Dimensional ◽  
Type Structure ◽  
Rare Earth Compounds ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray

The equiatomic rare earth compounds REPtZn (RE = Y, Pr, Nd, Gd-Tm) were synthesized from the elements in sealed tantalum tubes by high-frequency melting at 1500 K followed by annealing at 1120 K and quenching. The samples were characterized by powder X-ray diffraction. The structures of four crystals were refined from single-crystal diffractometer data: TiNiSi type, Pnma, a = 707.1(1), b = 430.0(1), c = 812.4(1) pm, wR2 = 0.066, 602 F2, 21 variables for PrPt1.056Zn0.944; a = 695.2(1), b = 419.9(1), c = 804.8(1) pm, wR2 = 0.041, 522 F2, 21 variables for GdPt0.941Zn1.059; a = 688.2(1), b = 408.1(1), c = 812.5(1) pm, wR2 = 0.041, 497 F2, 22 variables for HoPt1.055Zn0.945; a = 686.9(1), b = 407.8(1), c = 810.4(1) pm, wR2 = 0.061, 779 F2, 20 variables for ErPtZn. The single-crystal data indicate small homogeneity ranges REPt1±xZn1±x. The platinum and zinc atoms build up three-dimensional [PtZn] networks (265 - 269 pm Pt-Zn in ErPtZn) in which the erbium atoms fill cages with coordination number 16 (6 Pt + 6 Zn + 4 Er). Bonding of the erbium atoms to the [PtZn] network proceeds via shorter RE-Pt distances, i. e. 288 - 293 pm in ErPtZn.

Lewis-Base Adducts of Group 1B Metal(I) Compounds. XXI The Crystal and Molecular Structures of the Unsolvated Forms of Dibromotris(triphenylphosphine)dicopper(I) and 'step' Tetrabromotetrakis(triphenyl-phosphine)tetracopper(I)

1985 ◽  
Vol 38 (8) ◽  
pp. 1243 ◽  
Author(s):  
JC Dyason ◽  
LM Engelhardt ◽  
C Pakawatchai ◽  
PC Healy ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Molecular Structures ◽  
Lewis Base ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Triphenyl Phosphine ◽  
X Ray ◽  
Crystal And Molecular Structures

The crystal structures of the title compounds have been determined by single-crystal X-ray diffraction methods at 295 K. Crystal data for (PPh3)2CuBr2Cu(PPh3) (1) show that the crystals are iso-morphous with the previously studied chloro analogue, being monoclinic, P21/c, a 19.390(8), b 9.912(5), c 26.979(9) Ǻ, β 112,33(3)°; R 0.043 for No 3444. Cu( trigonal )- P;Br respectively are 2.191(3); 2.409(2), 2.364(2) Ǻ. Cu(tetrahedral)- P;Br respectively are 2.241(3), 2.249(3); 2.550(2), 2.571(2) Ǻ. Crystals of 'step' [PPh3CuBr]4 (2) are isomorphous with the solvated bromo and unsolvated iodo analogues, being monoclinic, C2/c, a 25.687(10), b 16.084(7), c 17.815(9) Ǻ, β 110.92(3)°; R 0.072 for No 3055. Cu( trigonal )- P;Br respectively are 2.206(5); 2.371(3), 2.427(2) Ǻ. Cu(tetrahedral)- P;Br are 2.207(4); 2.446(2), 2.676(3), 2.515(3) Ǻ.

Die neuen Oxobismutate(III) Cs6Bi4O9, K9Bi5O13 und A2Bi4O7 (A = Rb, Cs) / The New Oxobismutates(III) Cs6Bi4O9, K9Bi5O13 and A2Bi4O7 (A = Rb, Cs)

2002 ◽  
Vol 57 (10) ◽  
pp. 1090-1100
Author(s):  
Franziska Emmerling ◽  
Caroline Röhr
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Alkali Metals ◽  
Mixed Valence ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Trigonal Bipyramidal ◽  
Mixed Valence Compound

AbstractThe title compounds were synthesized at a temperature of 700 °C via oxidation of elemental Bi with the hyperoxides AO2 or via reaction of the elemental alkali metals A with Bi2O3. Their crystal structures have been determined by single crystal x-ray diffraction. They are dominated by two possible surroundings of Bi by O, the ψ-trigonal-bipyramidal three (B) and the ψ-tetrahedral four (T) coordination. Cs6Bi4O9 (triclinic, spacegroup P1̄, a = 813.82(12), b = 991.60(14), c = 1213.83(18) pm, α = 103.658(2), β = 93.694(3), γ = 91.662(3)°, Z = 2) contains centrosymmetric chain segmentes [Bi8O18]12- with six three- (T) and two four-coordinated (B) Bi(III) centers. K9Bi5O13 (monoclinic, spacegroup P21/c, a = 1510.98(14), b = 567.59(5), c = 2685.6(2) pm, β = 111.190(2)°, Z = 4) is a mixed valence compound with isolated [BivO4]3- tetrahedra and chains [BiIII4O9]6- of two T and two B coordinated Bi. In the compounds A2Bi4O7 (A = Rb/Cs: monoclinic, C2/c, a = 2037.0(3) / 2130.6(12), b = 1285.5(2) / 1301.9(7), c = 1566.6(2) / 1605.6(9) pm, β = 94.783(3) / 95.725(9)°, Z = 8) ribbons [Bi4O6O2/2]2- are formed, which are condensed to form a three-dimensional framework.

Synthese und Struktur von Nb0,89Fe0,93Te2 und Ta0,77Fe0,90Te2 / Synthesis and Structure of Nb0.89Fe0.93Te2 and Ta0.77Fe0.90Te2

1992 ◽  
Vol 47 (9) ◽  
pp. 1203-1212 ◽  
Author(s):  
Jörg Neuhausen ◽  
Karl-Ludwig Stork ◽  
Elisabeth Potthoff ◽  
Wolfgang Tremel
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Chemical Transport ◽  
Structure Type ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
X Ray ◽  
The Relationship

Nb0.89Fe0.93Te2 and Ta0.77Fe0.90Te2 were prepared by chemical transport reactions. The crystal structures of both compounds were determined using X-ray single crystal methods. The structures of the layer compounds Nb0.89Fe0.93Te2 (Pmna, Z = 2, a = 7.951(1) Å, b = 7.241(1) A, c = 6.233(1) Å) and Ta0.77Fe0.90Te2 (Pmna, Z = 2, a = 7.890(2) Å, b = 7.252(2) Å, c = 6.192(1) Å) are based on a hexagonal close packing of Te atoms. Approximately one-half of the octahedral holes in this packing are occupied by Nb (Ta) atoms, about one-quarter of the tetrahedral holes are occupied by Fe atoms. The relationship to the NiAs structure type is discussed.

Oxide Structures: By Hook Or by Crook

1998 ◽  
Vol 4 (S2) ◽  
pp. 678-679
Author(s):  
L. D. Marks ◽  
W. Sinkler ◽  
H. Zhang
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Dynamic Range ◽  
Unit Cell ◽  
Crystal Data ◽  
Large Dynamic Range ◽  
Phase Purity ◽  
X Ray ◽  
True Structure

Sometimes oxides are friendly; x-ray or neutron diffraction solves the structure and (at most) simple HREM does a double check. Sometimes they are not. Problems can range from phase purity (identifiable using EDX) to more subtle issues about the true unit cell and/or atom locations. The latter are often particularaly hard for x-ray or neutron to handle when single crystal data is not available and, for instance, the samples are polyphase or textured.One common problem is that the unit cell is rather larger than originally thought due to a superstructure. While superstructure reflections may be obvious in the microscope due to the very large dynamic range of TED patterns, they may not show in powder patterns. The issue then is to determine the true structure using (often) a combination of HREM and TED plus multislice simulations to confirm the structure.

Structural studies of ligands for the glycine binding site of the excitatory amino acid receptor complex: 2. 6-bromo-, 6-methyl-, and 6-styryl-1,8-ethano-4-hydro-2,3-quinoxalinedione

1994 ◽  
Vol 72 (10) ◽  
pp. 2028-2036 ◽  
Author(s):  
Maciej Kubicki ◽  
Teresa W. Kindopp ◽  
Mario V. Capparelli ◽  
Penelope W. Codding
Keyword(s):  
Hydrogen Bond ◽  
Binding Site ◽  
Crystal Structures ◽  
Excitatory Amino Acid ◽  
Glycine Receptor ◽  
Three Dimensional ◽  
Unit Cell ◽  
Geometric Constraints ◽  
Cell Parameters ◽  
Π Stacking

The crystal structures of three tricyclic quinoxalinedione derivatives, 6-bromo-1,8-ethano-4-hydro-2,3-quinoxalinedione (1), 6-methyl-1,8-ethano-4-hydro-2,3-quinoxalinedione hydrate (2), and 6-styryl-1,8-ethano-4-hydro-2,3-quinoxalinedione (3), are reported. For 1 and 2, the space groups are P21/n with the unit cell parameters for 1: a = 7.4003(5) Å, b = 8.5799(5) Å, c = 14.3127(9) Å, β = 90.639(6)°, and for 2: a = 7.0590(2) Å, b = 10.7483(3) Å, c = 13.9509(7) Å, β = 103.290(3)°. For 3, the space group is P21/c, with a = 19.3683(10) Å, b = 8.0962(16) Å, c = 19.5801(16) Å, β = 114.028(6)°. Compound 3 crystallizes with two molecules in the asymmetric part of the unit cell; in one of them the styryl group is disordered. The geometries of the 1,8-ethano-4-hydro-2,3-quinoxalinedione fragments are similar in all observations, with the differences mainly caused by the different nature of the substituents in the 6-position. Hydrogen bonds connect the molecules into three-dimensional networks. Head-to-tail π-stacking between molecules connected by a center of symmetry determines the packing modes in 1 and 2 but there is no π-stacking in the crystal structure of 3. The crystal structures of the three quinoxaline derivative ligands for the glycine receptor suggest a mode of recognition that involves an [Formula: see text]receptor hydrogen bond, a three-centre hydrogen bond to the neighboring carbonyl groups on the ligand, and π-stacking between ligand and receptor. This mode is consistent with the geometric constraints of the current binding site model but places greater emphasis on hydrogen-bond interactions.

Redefinition of satimolite

2018 ◽  
Vol 82 (5) ◽  
pp. 1033-1047 ◽  
Author(s):  
Igor V. Pekov ◽  
Natalia V. Zubkova ◽  
Dmitry A. Ksenofontov ◽  
Nikita V. Chukanov ◽  
Vasiliy O. Yapaskurt ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Rietveld Method ◽  
Three Dimensional ◽  
Direct Methods ◽  
Salt Dome ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Octahedral Clusters

ABSTRACTThe borate mineral satimolite, which was first described in 1969 and remained poorly-studied until now, has been re-investigated (electron microprobe analysis, single-crystal and powder X-ray diffraction studies, crystal-structure determination, infrared spectroscopy) and redefined based on the novel data obtained for the holotype material from the Satimola salt dome and a recently found sample from the Chelkar salt dome, both in North Caspian Region, Western Kazakhstan. The revised idealized formula of satimolite is KNa2(Al5Mg2)[B12O18(OH)12](OH)6Cl4·4H2O (Z = 3). The mineral is trigonal, space group R$\bar{3}$m, unit-cell parameters are: a = 15.1431(8), c = 14.4558(14) Å and V = 2870.8(4) Å3 (Satimola) and a = 15.1406(4), c = 14.3794(9) Å and V = 2854.7(2) Å3 (Chelkar). The crystal system and unit-cell parameters are quite different from those reported previously. The crystal structure of the sample from Chelkar was solved based on single-crystal data (direct methods, R = 0.0814) and the structure of the holotype from Satimola was refined on a powder sample by the Rietveld method (Rp = 0.0563, Rwp = 0.0761 and Rall = 0.0667). The structure of satimolite is unique for minerals. It contains 12-membered borate rings [B12O18(OH)12] in which BO3 triangles alternate with BO2(OH)2 tetrahedra sharing common vertices, and octahedral clusters [M7O6(OH)18] with M = Al5Mg2 in the ideal case, with sharing of corners between rings and clusters to form a three-dimensional heteropolyhedral framework. Each borate ring is connected with six octahedral clusters: three under the ring and three over the ring. Large ellipsoidal cages in the framework host Na and K cations, Cl anions and H2O molecules.

Structure of caesium disulfate at 120 and 273 K

2009 ◽  
Vol 65 (5) ◽  
pp. 551-557 ◽  
Author(s):  
Kenny Ståhl ◽  
Rolf W. Berg ◽  
K. Michael Eriksen ◽  
Rasmus Fehrmann
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Metal Structure ◽  
Structure Type ◽  
The Other ◽  
Crystal Data ◽  
Remarkable Similarity ◽  
Disorder Transition ◽  
X Ray

The crystal structures of Cs2S2O7 at 120 and 273 K have been determined from X-ray single-crystal data. Caesium disulfate represents a new structure type with a uniquely high number of independent formula units at 120 K: In one part caesium ions form a tube surrounding the disulfate ions, [Cs8(S2O7)6+] n ; in the other part a disulfate double-sheet sandwiches a zigzagging caesium ion chain, [Cs2(S2O7)6−] n . Caesium disulfate shows an isostructural order–disorder transition between 230 and 250 K, where two disulfate groups become partially disordered above 250 K. The Cs+-ion arrangement shows a remarkable similarity to the high-pressure RbIV metal structure.

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