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  • 1
    ISSN: 1435-1528
    Keywords: Vectra B950 ; thermotropic LCP ; rheology ; structure ; orientation ; transients ; dynamic moduli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The structure changes in the start-up flow of the thermotropic liquid crystalline polymer Vectra 8950 are probed by performing transient experiments after various flow histories. The shear and normal stress growth curves of a squeezed sample and of a randomly oriented sample show a pronounced overshoot at low strains, whereas the stress growth curve of a sample pre-sheared until steady state shows a gradual increase. This first peak is associated with the re-orientation of the director into the shearing plane. All stress transients show a second broad maximum at large strains that results from the generation of a steady defect network. The effect of varying the relaxation period after pre-shearing is reflected in the appearance of two peaks in the subsequent stress growth curves. One of these peaks shifts linearly with re laxation period and the other is more or less fixed in position. The orientation of the molecules during steady shear flow is on average in the flow direction. Intermediate orientation levels may exist in the transient depending on the amount of strain. The material is able to maintain the flow-induced orientation distribution for a long time after cessation of flow. This is reflected in a similar fashion in the initial magnitudes of the stresses and the dynamic moduli after various preshear strains. Moreover, the dynamic moduli decrease with time after cessation of steady shear flow, indicating that the orientation increases during relaxation.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical crystallography 25 (1995), S. 25-28 
    ISSN: 1572-8854
    Keywords: Oxathiazolone ; structure ; nitrile sulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of 5-phenyl-1,3,4-oxathiazol-2-one has been determined. Colorless, regular plate shaped crystals of C8H5O2NS crystallize in the monoclinic space group P21/n (#14) with cell dimensionsa=11·161(8),b=7·1470(20),c=19·864(15) Å and β=99·77(4)°;V=1561·5(17) Å3 andZ=8.1725 unique reflections withl net〉2.5σ(l) on refinement afforded values ofR=0.054 andR w=0.049.
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  • 3
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    Springer
    Journal of chemical crystallography 26 (1996), S. 539-542 
    ISSN: 1572-8854
    Keywords: Tricyclohexylmethyl chloride ; structure ; tricylohexylmethyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystallographic structure of tricyclohexylmethyl chloride, a precursor of the tricyclohexylmethyl radical, has been determined. Colourless tablets of C19H33Cl crystallized from hexane/chloroform in the orthorhombic space group Pnma, with cell dimensions a=10.725(3),b=15.670(3),c=10.168(3) Å;V=1708.8(1.3) Å3;Z=4. 1586 reflections withI〉3 σ(I), and 302 with zero intensity, on refinement gaveR=0.046,R w=0.076. The three cyclohexyl rings are arranged to give the molecule a plane of symmetry containing the central C−H axis. The large volume per nonhydrogen atom, of about 21.3 Å3, is close to values found in the crystal structures of analogous tricyclohexyl compounds.
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  • 4
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    Journal of chemical crystallography 29 (1999), S. 207-210 
    ISSN: 1572-8854
    Keywords: Tripodal ligand ; Ni(II) complex ; quinoline ; carbinoxyamine ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Treatment of Ni(ClO4)2 · 6H2O with the condensing product of 2-formylpyridine N-oxide and 1,5-diamino-3-(8-methylquinolyl)azapentane (dmqa) has resulted in the formation of an asymmetric tripodal nickel(II) complex, [C28H32N6O3Ni](ClO4)2 · H2O, which has been crystallographically characterized. Crystal data: triclinic, space group p ī, a = 10.384(2), b = 10.911(3), c = 16.6101(11) Å, α = 95.62(2), β = 105.04(2), γ = 112.954(11)°, D c = 1.581 g/cm3, Z = 2 and V = 1631.0(6) Å3. A quinoline moiety is first introduced into an arm in the complex of a tripodal ligand in which an ethylcarbinoxyamine group, the intermediate of Schiff bases, exists.
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  • 5
    ISSN: 1572-8854
    Keywords: structure ; conformation ; equatorial ; axial orientations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Single crystal X-ray studies for N-formyl-2,6-diortho chlorophenyl-3,5-dimethyl piperidin-4-one (FOCDMPO) and N-nitroso-2,6-di(3′,4′,5′-trimethoxyphenyl)-3,5-dimethyl piperidin-4-one (NTMPO) are reported. Crystals of FOCDMPO and NTMPO belong to the monoclinic space groups P21/n and C2/c, respectively. FOCDMPO: a = 9.147(2), b = 14.586(3), c = 13.665(5) Å and β = 101.68(2)° NTMPO: a = 38.52(2), b = 13.727(5), c = 9.564(3) Å and β = 98.60(1)°. In both the structures, the piperidine ring adopts a boat conformation with slight distortion. In FOCDMPO, one of the phenyl and methyl groups are in axial positions while the other phenyl and methyl groups are in equatorial orientations. In NTMPO, the situation is reversed. The molecules are stabilized by weak intermolecular C—H ··· O interactions in addition to van der Waals forces.
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  • 6
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    Journal of chemical crystallography 29 (1999), S. 671-676 
    ISSN: 1572-8854
    Keywords: nitroguanidine ; energetic molecule ; structure ; oxidizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of nitroguanidine was refined using X-ray single-crystal diffraction methods. Previous structure determinations achieved with single crystal photographic or neutron powder techniques yielded values for the C—N ‘formal’ double bond-length that either equaled or exceeded the ‘formal’ C—N single-bond lengths. Bond lengths were more precisely and accurately determined here than in the previous studies, but the ‘formal’ double-bond length still exceeds the ‘formal’ single bond lengths. Comparisons of crystal bond lengths with ab initio derived bond lengths of an isolated nitroguanidine molecule and hydrogen-bonded clusters of nitroguanidine molecules suggest that observed bond-length abnormalities are caused by intermolecular forces in the crystal. The crystal is orthorhombic, with a = 17.6390(5), b = 24.8730(7), c = 3.5903(1) Å, V = 1575.19 Å3, Z = 16, and D calc = 1.736 g cm−3.
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  • 7
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    Journal of cluster science 9 (1998), S. 393-415 
    ISSN: 1572-8862
    Keywords: Fullerene ; transition-metal ; complex ; synthesis ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A review of the chemistry of transition metal-[C60]fullerene complexes is presented. The main focus is directed toward the different methodologies for obtaining both metal bound and ligand bound complexes of C60, and the different types of structures which have been so far identified for metal-C60 complexes.
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  • 8
    ISSN: 1572-8862
    Keywords: Cobalt (iron) complexes ; thiolate ; phosphine ; structure ; synergism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Mono-, di-, tri-, and tetra-nuclear cobalt (iron) complexes containing co-ligands phosphine and thiolate are presented according to the classification by combination of different dentates of the two ligands. Emphasis is being put on the triand tetranuclear cluster complexes of monodentate phosphines and 1,2-bidentate thiolates. These complexes are considered to be constructed based on the general structural fragment (or building block) ML 2L′ (L=1,2-bidentate thiolate,L′=tertiary phosphine). Structural regularities are presented in Tables I, III, IV, and V and discussed. FAB mass spectroscopic data showed the possible fragmentation patterns. Synergism of the cluster skeletons is proposed to explain the occurrence of the distinct structural modes.
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  • 9
    ISSN: 1572-8854
    Keywords: Cyclooligomerization ; orthocyclophanes ; structure ; X-ray diffraction ; C−H...O molecular interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 3,4,5-Trimethoxybenzyl alcohol was cyclooligomerized with a bentonite clay used as a catalyst. Results of the crystal structure analysis of the racemic (±) nonamethoxy[1,1,1]orthocyclophane trimer, C30H36O9, are described. The structure was determined by X-ray diffraction at 293 K and shown to belong to the triclinic space group P $$\bar 1$$ . The compound possesses a distorted crown conformation with unusual C−H...O intermolecular interactions, and with a crystal packing not observed before in other related derivatives. The racemic mixture was also discriminated in its two enantiomeric isomers, using proton NMR and Eu(III) as a chiral shift reagent.
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  • 10
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    Journal of chemical crystallography 26 (1996), S. 9-13 
    ISSN: 1572-8854
    Keywords: Lanthanum ; hexaazamacrocyclic complex ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the [5S,15S] isomer of the [LaL(NCS)3] complex (L=C26H30N6) was determined by single crystal X-ray diffraction analysis. The compound crystallizes in the orthorhombic space group P212121 witha=13.647(4),b=19.504(4),c=11.606(4)Å. The 9-coordinate La(III) is bound to the N atoms of three monodentate isothiocyanates and to the six N atoms of the macrocycle ligand L, which has an 18-membered, six-nitrogen donor cavity and two peripheral −CH3 substituents.
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  • 11
    ISSN: 1572-8854
    Keywords: Triazole ; triazene ; Ni(II) ; structure ; spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound [Ni(batt)2]·4H2O, in which Hbatt is 1,3-bis[3-(5-amino-1,2,4-triazolyl)]triazene, has been prepared and its crystal structure determined by X-ray diffraction methods. The compound crystallizes in the tetragonal space group I4/m (a = 10.5645(8) Å, c = 9.1336(6) Å, and Z = 2). The Ni(batt)2 molecule has local 4¯ symmetry, but it is located on a crystallographic 4/m site and is disordered over the mirror plane. The ligand batt− is tridentate with nitro-type coordination of the triazenido group and N4 coordination of the two outer triazolyl substituents. The complex has a distorted octahedral geometry with meridional configuration of the two nearly planar batt− ligands. The geometry of the tridentate cavity is examined and a comparison is made with the Ni-terpyridyl system, which shows similar coordination around the nickel center. The FTIR, micro-Raman, and UV-vis spectra are analyzed in relation with the structure.
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  • 12
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    Journal of chemical crystallography 29 (1999), S. 1287-1290 
    ISSN: 1572-8854
    Keywords: organic phosphate ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The salt triethylentetraammonium bis monohydrogen-monophosphate dihydrate is orthorhombic Pbca with unit cell dimensions a = 8.963(2), b = 10.326(2), c = 17.381(4)Å; Z = 4; Dm = 1.540 g cm−3; D x = 1.562 g cm−3. The examination of the structure shows a layer arrangement parallel to the $${\bar c}$$ axis: planes of [HPO4]2− tetrahedra alternate with planes of [(NH3(CH2)2NH2CH2)2]4+. The [HPO4]2− tetrahedra are connected through O(W)s--H···O hydrogen bonds, so that infinite chains of the composition [HPO4(H2O)]n 2n− are formed in the structure parallel to the $${\bar b}$$ axis. The structure of this compound is built from [HPO4]2− anions, [(NH3(CH2)2NH2CH2)2]4+ cations and zeolitic water molecules connected by hydrogen bonds.
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  • 13
    ISSN: 1572-8854
    Keywords: organic phosphate ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The salt triethylentetraammonium bis monohydrogenmonophosphate dihydrate is monoclinic with the following unit cell dimensions: a = 8.462(1), b = 10.500(1), c = 9.520 Å, β = 99.297(1)°, space group P21/n with Z = 2. The structure was solved by the Patterson method and refined to final R value of 0.043 for 1590 independent reflections. The structure consists of infinite parallel two-dimensional [ $$\bar 1$$ 01] planes built of mutually connected ions and water molecules by strong O—H· · ·O and N—H· · ·O hydrogen bonding.
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  • 14
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    Journal of cluster science 11 (2000), S. 253-260 
    ISSN: 1572-8862
    Keywords: magnesium ; cluster ; hydroxide ; structure ; fluxionality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A novel Mg6 cluster molecule with the formula of Mg6(μ 3-OH)2(μ 3-Br)2(μ-Br)8(THF)8 (1) has been isolated in 38% yield from a reaction of the Grignard reagent, 2-naphthyl-Mg-Br with BBr3 in THF. The structure of 1, determined by a single-crystal X-ray diffraction analysis, contains two Mg3 triangles linked together by two bridging bromide ligands. Within each Mg3 triangle, one hydroxide and one bromide ligand function as triply bridging ligands capping both sides of the Mg3 triangle. The coordination geometry around each Mg(II) ion is approximately octahedral. NMR studies revealed that compound 1 is highly fluxional in solution.
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  • 15
    ISSN: 1572-8862
    Keywords: Carbonyl ; osmium ; tin ; phosphine ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Pyrolysis a the cluster Os3(µ-H h (CO)10 (SnMe2 H) produced an as yet unidentified purple duster, which upon reaction with PEt2Ph at room temperature, gave essentially a quantitative yield of the cluster Os3(µ-H)3(CO)9(µ3-Sn) Os3(µ-H)(CO)10(PEt2Ph), 4. The X-ray structure of 4 (as the toluene solvate) shows that it consists Or two Os, triangles linked through a µ4-Sn unit, such that one of the Os3 triangle is µ3-bonded to the Sn atom (Os-Sn range 2.689(2)–2.707(2) Å) and the other is bonded via a single covalent bond (Os-Sn = 2.643(2) Å). The phosphine ligand occupies the equatorial site on a second osmium atom a be latter Os3 moiety that is syn to the Sn atom; the unique bridging hydride ligarid is believed to occupy a site that Acis to both the P and Sn atoms. Crystallographic data for compound4. 0.5C7H8: space group,P $$\bar 1$$ ; ca= 11862(4) Å,b = 12.940(4) Å,c = 16.513(5) Å, α=68.96(3),β=80.60(3)°,γ=62.49(2).R=0.029, 4118 observed reflections.
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  • 16
    ISSN: 1572-8862
    Keywords: Iron ; ynamine ; aminoalkyne ; diazoalkane ; carbene ; C-N coupling ; insertion ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The diiron ynamine complex [Fe2(CO)7{μ-CR)C(NEt2)}] (1:R=Me,2:R = C3H5.3:R=SiMe3.4:R = Ph) reacts at room temperature with diphenyldiazomethane Ph2CN2, in hexane to yield complexes [Fe2(CO)6{C(R)C(NEt2)N (NCPh2)] (5a:R=Me,6a:R=C3H5.7a R=SiMe3.8a:R=Ph) resulting from the insertion of the terminal nitrogen atom into the Fe=C carbene bond. Insertion the second nitrogen atom and formation of compounds [Fe2(CO)6zμ-C(R)C(NEt2)NN(CPh2)}] (5b:R=Me,6b:R=C3H5,7b:R=SiMe3,8b:R=Ph) is observed when compounds5a-5a are treated in refluxing hexane. Transformation of compoundsa tob is also obtained at room temperature within a few days. All compounds were identified by their1H NMR spectra. Compounds6a, 7a, 8a, and8b were characterized by single crystal X-ray diffraction analyses. Crystal data: for6a: space group = P21/n,a=12.853(1) A,b=24.800(7) A,c=8.947(6) A,β=99.29(3)°,Z=4, 2227 rellectionsR=0,038; for7a: space group=Pl,a=ll.483(4) A,b=14.975(4) A,c = 17.890(8) A,α = 82.80(3)°,β=94.29(7)°,γ=85.42(2),Z = 4, 5888 reflectionR = 0.035: for8a: space group = Pcab.a = 31.023(8) A.b=20.137(1) A.c=9.686(2) A.Z=8. 1651 reflections,R=0.071; for8b: space group=P21/n,a=21.459(4),b=10,100(3) A,c=28,439(8) A,ß=103.86(4)°,Z=8. 2431 reflections.R=0.057.
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  • 17
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    Journal of chemical crystallography 25 (1995), S. 11-14 
    ISSN: 1572-8854
    Keywords: Adamantane ; dicarbonamide ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of 1,3-adamantane-dicarbonamide† has been determined. Colourless, cube shaped crystals of C12H18N2O2 crystallize in the monoclinic space group C2/c (#15) with cell dimensionsa=7·934(3),b=15·543(3),c=9·404(2) Å, β=93.63°;V=1157.4(5) Å3 andZ=4.1074 unique reflections withI net 〉2.00σ(I) on refinement afforded values ofR=0.039 andR w =0.040.
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  • 18
    ISSN: 1572-8854
    Keywords: Derivatives ; rotamers ; 1H-NMR ; x-ray ; structure ; 2,3,4, tri-O-acetyl-6-X-α-D-glucopyranosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The rotamers about the C(5)–C(6) bond of a series of 2,3,4-tri-O-acetyl-6-X-α-D-glucopyranozide derivatives resulting by substitution at C(6) or O(6) have been studies with1H-NMR spectroscopy (400 MHz) and X-ray structure analysis. The methyl 2,3,4-tri-O-acetyl-6-O-triphenylmethyl-α-D-glucopyranoside and the N-(I-O-methyl-2,3,4-tri-O-acetyl-α-D-glucopyranose-6-yl)-pyridinium nitrate crystallize in the P21 space group with α=14.940(1),b=11.232(1),c=9.0773(7), and β=94.480(7) anda=7.670(1),b=15.384(3),c=9.624(1) and β=104.90(1), respectively; the methyl 2,3,4-tri-O-acetyl-6-O-nitro-α-D-glucopyranoside and methyl 2,3,4-tri-O-acetyl-6-O-deoxy-6-iodo-α-D-glucopyrano-side crystallize in the P212121 space group witha=5.630(1),b=14.360(1) andc=22.388(3), anda=5.556(1),b=14.303(6) andc=21.963(6), respectively.
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  • 19
    ISSN: 1572-8854
    Keywords: Terbium ; hexaazamacrocyclic complex ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title complex was obtained by anion metathesis from [Tb(CH3COO)2(C22H26N6)] (CH3COO)·4H2O and K2CrO4 in aqueous solution. The compound crystallizes in the triclinic space group $$P\bar 1$$ witha=8.384(2),b=10.425(2)c=15.752(2)Å, α=98.82(2), β=93.52(2), γ=97.22(2)°, andZ=2. The structure is ionic and consists of a (+1) complex cation balanced in a 2∶1 ratio by a disordered dichromate ion. The 9-coordinate Tb(III) is linked to the six nitrogen atoms of the macrocyclic ligand L=C22H26N6, as well as to a water molecule and a bidentate chelating chromate situated on opposite sides of the macrocycle. The infrared spectrum shows, in addition to the pattern of the macrocyclic ligand, the absorptions arising from the stretching modes of the bidentate chelating CrO4 2− ligand and of the Cr2O7 2− counterion.
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  • 20
    ISSN: 1572-8854
    Keywords: 2-thio-6-picoline N-oxide ; structure ; cobalt(III) ; copper(II) ; nickel(II) ; zinc(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Structures of the following compounds have been solved: tris(2-thio-6-picoline N-oxide)cobalt(III), [Co(6MOS)3], orthorhombic, Pca21, a = 17.871(3), b = 14.061(2), c = 15.964(2) Å, V = 4011(1) Å3, Z = 8, and μ = 1.193 mm−1; bis (2-thio-6-picoline N-oxide)nickel(II), [Ni(6MOS)2], orthorhombic, Pbca, a = 15.602(8), b = 13.606(4), c = 13.348(8) Å, V = 2833(4) Å3, Z = 8, and μ = 1.655 mm−1; bis(2-thio-6-picoline N-oxide)copper(II), [Cu(6MOS)2], orthorhombic, Pbca, a = 13.914(5), b = 12.984(5), c = 15.663(6) Å, V = 2830(2) Å3, Z = 8, and μ = 1.836 mm−1; and bis(2-thio-6-picoline N-oxide)zinc(II), [Zn(6MOS)2], triclinic, P − 1, a = 7.9737(8), b = 11.7786(9), c = 7.9206(8) Å, α = 104.502(7), β = 104.495(8), γ = 93.445(8)°, V = 691.3(1) Å3, Z = 2, and μ = 2.106 mm−1. The steric effect of the methyl group in the six-position of the N-oxide ring is considered in comparing these structures to complexes of 2-thiopyridine N-oxide.
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  • 21
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    Journal of chemical crystallography 28 (1998), S. 197-201 
    ISSN: 1572-8854
    Keywords: Yttrium(III) ion ; crown ether ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The complex [Y(NO3)3(OH2)3]·(Me2-16-crown-5)·H2O has been prepared and its crystal and molecular structure determined using single crystal X-ray diffraction. The colorless crystals belong to the monoclinic space group P21/n with Z = 4. Lattice parameters are a = 10.420(1), b = 17.257(3), c = 14.646(2) Å, β = 96.79(1)°, V = 2615.1(6) Å3. The yttrium(III) ion is nine-coordinate, bonded to three bidentate nitrate groups and three water molecules. The average Y–O(nitrate) and Y–O(water) distances are 2.42(3) and 2.33(1) Å, respectively. The average HO–H···O hydrogen bonded separation is 2.767Å.
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  • 22
    ISSN: 1572-8854
    Keywords: Organic phosphate ; structure ; nonlinear optical material
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The salt N-benzylmethylammonium dihydrogenmonophosphate monohydrate is monoclinic with the following unit cell dimensions: a = 6.356(1)Å, b = 8.385(7)Å, c = 11.472(5)Å, β = 104.32(1)°, space group P21 with Z = 2. The structure consists of infinite parallel two-dimensional [110] planes built of mutually connected ions and water molecules by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than normal van der Waals interactions between the layers.
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  • 23
    ISSN: 1572-8854
    Keywords: Azole ; triazene ; Pd(II) ; Cu(II) ; structure ; Raman
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the complex [Pd(batt)Cl]·CH3OH, in which Hbatt is 1,3-bis[3-(5-amino-1,2,4-triazolyl)]triazene, has been determined by X-ray diffraction methods. The crystals are triclinic, space group $$P_{\bar 1} $$ (a = 10.1883(9) Å, b = 10.5095(8)Å, c = 13.1760(11) Å, α = 94.518(6)°, β = 109.040(7)°, γ = 113.678(7)°; Z = 4). The deprotonated batt− ligand exhibits terdentate chelate coordination with a new nitro-type ligation mode of the triazenido group and N4 coordination of the two outer triazolyl substituents. The asymmetric unit contains two crystallographically independent, almost parallel Pd(batt)Cl molecules with Pd–Pd contacts of 3.4584(7)Å and two independent methanol molecules. The complexes are packed in a layer structure with numerous intermolecular H-bond connections. Raman spectra have been recorded for various excitation wavelengths along the contour of the intense triazenido π-π* absorption band at 465 nm and resonance profiles measured for the most important Raman bands. A comparison is made with the analog [Cu(batt)Cl] complex. Structural and spectral differences between the two molecules are emphasized and related to differences in metal-ligand bonding.
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  • 24
    ISSN: 1572-8854
    Keywords: binuclear ; copper(II) ; sulfato bridges ; structure ; 3-azacyclothiosemicarbazone
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    Topics: Geosciences , Physics
    Notes: Abstract Structures of two binuclear copper(II) complexes with sulfato bridges and tridentate 2-acetylpyridine 3-azacyclothiosemicarbazone ligands have been solved. The complexμ-sulfato-bis{(2-acetylpyridine 3-hexamethyleneiminyl-thiosemicarbazonato)copper(II)} N,N-dimethylformamide, [Cu(Achexim)]2SO4·DMF, has the following structural properties: triclinic, P1¯(#2), a = 12.314(4), b = 15.885(4), c = 10.959(4) Å, α = 103.25(2), β = 103.60(2), γ = 109.94(2)°, V = 1843(2) Å3, and Z = 2; for μ-sulfato-bis{(2-acetylpyridine 3-piperidylthiosemicarbazonato)copper(II)}chloroform, [Cu(Acpip)]2SO4·CHCl3: triclinic, P1¯(#2), a = 11.657(1), b = 17.101(2), c = 10.338(1) Å, α = 98.51(1), β = 109.294(7), γ = 107.016(9)°, V = 1790.3(4) Å3, and Z = 2. The size of the azacyclo ring significantly affects the stereochemistry of these binuclear complexes.
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  • 25
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    Journal of chemical crystallography 29 (1999), S. 1173-1186 
    ISSN: 1572-8854
    Keywords: pyrroline derivative ; structure ; polymeric chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the space group P21/c, with a = 8.555(2), b = 22.109(2), c = 16.768(2) Å, and β = 90.25(2)°, with two independent molecules in the asymmetric unit, dissimilar only for the orientation of the xylenyl group. There is no conjugation between the pyrroline ring and the xylenyl group. The molecules in the asymmetric unit are enantiomers, thus constituting a racemic dimer. The molecules are linked in chains by hydrogen bonds.
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  • 26
    ISSN: 1572-8854
    Keywords: structure ; thiosemicarbazide ; infrared ; nmr ; hydrogen-bonding
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    Topics: Geosciences , Physics
    Notes: Abstract The structures of two thiosemicarbazones are described: syn,E-1-cyclopentano-4-ethyl-3-thiosemicarbazone (1) and syn,E-1-cyclopentano-4-phenyl-3-thiosemicarbazone (2). Crystal data: for 1: tetragonal, P43 (#78), a = b = 8.922(7) Å, c = 12.899(13) Å, and Z = 4; for 2: monoclinic a = 15.163(18) Å, b = 7.482(5) Å, c = 12.467(15) Å, β = 119.04(7)°, and Z = 4. In 1, molecules are linked by hydrogen-bonding into infinite chains with non-planar 9-ring subunits in which thioamides interact with the H—N—C—N—N groups of neighbors. Thioamide groups in 2 form dimers linked by N—B···HS hydrogen-bonds with a planar 8-ring as in solid state structures of carboxylic acids. The semicarbazide syn conformation fosters formation of N—H···N intramolecular hydrogen-bonding in each structure. The solid state structures are consistent with their infrared and proton nuclear magnetic resonance spectra.
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  • 27
    ISSN: 1572-8862
    Keywords: Carbonyl ; osmium ; tin ; lead ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The complexes [(OC)4Os(PbMe2)]2 (3) and [(OC)4OsSnBu 2 ′ ]2 (4) have been prepared from be reaction of Na2[Os(CO)4] with Me2PbCl2 and Bu 2 ′ SnCl2, respectively, in THF and their X-ray crystal structures determined. The red derivative,3, was light-sensitive in solution. The reactions or [(OC)4 Os(SnMe2)]2 (2), or its decarbonylated derivative [Os3(CO)7(SnMe2)2]2 (7), with olefins or phosphorus donor ligands have also been investigated, and the structures of two derivatives, viz. [Os2(CO)7(SnMe2)2(C2H4)] (5a) and [Os2(CO)7(SnMe2)2(PMe3)] (6a), have been determined; the noncarbonyl ligand occupies an equatorial site in each case. The X-ray crystal structures of all these compounds, like those of [(OC)4Os(EMe2)]2 (E=Ge (1), Sn (2)) which have been reported previously, show leaning of the axial carbonyl ligands toward the metal tetracycle, i.e., an “umbrella” effect. Crystallographic data for compound3: space group, P21/a;a=13.4404(13) Å,b=10.7494(14) A,c=148967(18) A,β=98.204(9)°,R=0.035, 1983 observed reflections. For compound4: space group,P1;a=9.016(1) Å,b=9.370(1),c=11.334(1) A, α=103.67(1)°,β=100.30(1)°, γ=115.03(1)°, R=0.046, 2026 observed reflections. For compound5a: space group,P1;a=9.2933(11)Å,b=9.7181(3),c=12.2508(15) A, α=89.21(1)°,β=87.61(1)°, γ=86.13(1)°,R=0.038, 2770 observed reflections. For compound6a space groupP1:a=8.7244(9)Å,b=10.9318(6),c=13.2560(13) A, α=87.815(6)°,β=83.655(8)°, γ=82.343(6)°, R=0.030, 3497 observed reflections.
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  • 28
    ISSN: 1572-8862
    Keywords: Platinum ; mercury ; ruthenium ; heteronuclear ; cluster ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Addition of a THF solution prepared by stirring [CpRu(CO)2]2 over Na/Hg amalgam to a solution of the triplatinum cluster [Pt3(dppm)3(CO)][PF6]2 (1) in THF gives the heteronuclear cluster [Pt3(dppm)3{(μ4-Hg)–RuCp(CO)2}2] [PF6]2 (2) in 40% yield following chromatography. A single crystal X-ray study of 2 reveals structural parameters for the Pt3Hg2 molecular core that are consistent with those of other structurally characterized complexes of this type. 1H, 13C, and 31P NMR spectra of this complex indicate that the structure observed in the solid state is retained in solution.
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  • 29
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    Journal of cluster science 6 (1995), S. 463-484 
    ISSN: 1572-8862
    Keywords: Copper (II) complex ; aminoalcohol ; structure ; synthesis ; magnetism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Copper complexes with aminoalcoholato ligands have attracted much attention recently because of their potential applications in ceramic materials. This review deals with polynuclear copper (II) complexes containing bidentate and triden-tate aminoalcoholato ligands. The focus of this article is on the synthesis, structure, and magnetic properties of polynuclear copper (II) complexes obtained recently by our group. Some relevant work reported previously by other researchers is also included.
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  • 30
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    Journal of cluster science 7 (1996), S. 435-453 
    ISSN: 1572-8862
    Keywords: Osmium ; thiolate ; carboxylate ; structure
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reaction of the lightly stablized cluster [Os3(CO)10(NCMe)2] with thiosalicylic acid affords two products [{Os3(CO)10(µ-H}]2SC6H4CO2],1 and [Os3H(CO)10SC6,H4C(O)OOs3H(CO)11],2. Complex 2 undergoes CO dissociation to give1 or fragmentation to give [Os3H(CO)10SC6H4 COOH], 3 in solution. Reaction of phthalic acid and [ Os3(CO)10(NCMc)2] gives two products [{Os3(CO)10(µ-H)}2O2CC6H4CO2], 4 and [Os3H(CO)10O2CC6 H4C(O)OOs3H(CO)11], 5. 5 also undergoes CO dissociation to give4, but no such conversion is observed in the preparation of [{Os3(CO)10(µH)}2 (SC6H4S)],6 from the reaction betweeno-dithiobenzene and [Os3(CO)10 (NCMe)2]. Unlike thiosalicylic acid, treatment of [Os3(CO)10(NCMe)2] with 1 equivalent 2,2'-dithiosalicylaldehyde in dichloromethane produces the compounds [Os3(CO)10(SC6H4CHO)2],7 and [Os3(CO)10µ-H)(SC6H4CHO)].8 in moderate yields which are stable in both the solid state and solution. The mechanism for the formation of1-5 is also proposed. All the clusters1-8 have been fully characterized by conventional spectroscopic methods and the structures of1, 3, 4, 7, and8 have been established by X-ray, crystallography.
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  • 31
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    Marine geophysical researches 21 (2000), S. 243-257 
    ISSN: 1573-0581
    Keywords: diapir ; mantle ; Oman ; ophiolite ; seamount ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Large scale structural mapping of the Oman ophiolite indicates that the Mansah area (Sumail massif) was a ridge off-axis region at the time the ophiolite was detached. This paper presents a detailed structural mapping of the region. We show that, as opposed to other off-axis areas, it contains plunging lineations, correlated with a thick Moho transition zone and chromite pods, indicative of a mantle diapir. However this diapir has a discontinuous structure, it is bounded by shear zones and types of diabases that are not found elsewhere in Oman; it also has a broken crust, strongly affected by hydrothermal alteration. This suggests that Mansah fossilized an off-axis diapir intruding a cooling lithosphere. It may be a good candidate to be the root of an off-axis seamount such as those found in the East Pacific, and may bring new insights into this particular volcanism which we are only beginning to explore.
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  • 32
    ISSN: 1573-0581
    Keywords: Petrology ; structure ; volcanism ; microplate
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    Topics: Geosciences , Physics
    Notes: Abstract The Easter microplate-Crough Seamount region located between 25° S–116° W and 25° S–122° W consists of a chain of seamounts forming isolated volcanoes and elongated (100–200 km in length) en echelon volcanic ridges oriented obliquely NE (N 065°), to the present day general spreading direction (N 100°) of the Pacific-Nazca plates. The extension of this seamount chain into the southwestern edge of the Easter microplate near 26°30′ S–115° W was surveyed and sampled. The southern boundary including the Orongo fracture zone and other shallow ridges (〈 2000 m high) bounding the Southwest Rift of the microplate consists of fault scarps where pillow lava, dolerite, and metabasalts are exposed. The degree of rock alternation inferred from palagonitization of glassy margins suggests that the volcanic ridges are as old as the shallow ridges bounding the Southwest Rift of the microplate. The volcanics found on the various structures west of the microplate consist of depleted (K/Ti 〈 0.1), transitional (K/Ti = 0.11−0.25) and enriched (K/Ti 〉 0.25) MORBs which are similar in composition to other more recent basalts from the Southwest and East Rifts spreading axes of the Easter microplate. Incompatible element ratios normalized to chondrite values [(Ce/Yb)N = 1−2.5}, {(La/Sm)N = 0.4−1.2} and {(Zr/Y)N = 0.7−2.5} of the basalts are also similar to present day volcanism found in the Easter microplate. The volcanics from the Easter microplate-Crough region are unrelated to other known South Pacific intraplate magmatism (i.e. Society, Pitcairn, and Salas y Gomez Islands). Instead their range in incompatible element ratios is comparable to the submarine basalts from the recently investigated Ahu and Umu volcanic field (Easter hotspot) (Scientific Party SO80, 1993) and centered at about 80 km west of Easter Island. The oblique ridges and their associated seamounts are likely to represent ancient leaky transform faults created during the initial stage of the Easter microplate formation (≈ 5 Ma). It appears that volcanic activity on seamounts overlying the oblique volcanic ridges has continued during their westward drift from the microplate as shown by the presence of relatively fresh lava observed on one of these structures, namely the first Oblique Volcanic Ridge near 25° S–118° W at about 160 km west of the Easter microplate West Rift. Based on a reconstruction of the Easter microplate, it is suggested that the Crough seamount (〈 800 m depth) was formed by earlier (7–10 Ma) hotspot magmatic activity which also created Easter Island.
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  • 33
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    Surveys in geophysics 16 (1995), S. 363-387 
    ISSN: 1573-0956
    Keywords: Magnetosphere ; plasma ; structure ; entry boundary ; geopause ; region-1 vortices ; lowenergy layer ; adiabacity boundary ; injection port
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Recent investigations of magnetospheric plasma structure are summarized under the broad categories of empirical models, transport across boundaries, formation, and dynamics of the plasma sheet. This report reviews work in these areas during the period 1991 to 1993. Fully three-dimensional empirical models and simulations have become important contributors to our understanding of the magnetospheric system. Some new structural concepts have appeared in the literature: the ‘entry boundary’ and ‘geopause’, the plasma sheet ‘region 1 vortices’, the ‘low-energy layer’, the ‘adiabaticity boundary’ or ‘wall region’, and a region in the tail to which we refer as the ‘injection port’. Traditional structural concepts have also been the subject of recent study, notably the plasmapause, the magnetopause, and the plasma sheet. Significant progress has been made in understanding the nature of plasma sheet formation and dynamics, but the acceleration of electrons to high energy remains somewhat mysterious.
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  • 34
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    Astrophysics and space science 224 (1995), S. 467-468 
    ISSN: 1572-946X
    Keywords: Molecular clouds ; HH24–26 ; abundances ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New J=1-0 HCO+ and J=2-1 C18O observations of HH24–26 reveal striking differences between these and previous maps of higher-J transitions of HCO+ and CS. The high-J HCO+ and CS emission traces the densest portions of the cloud, while C18O traces the more tenuous envelope. This is also evident in the velocity structure. HCO+ and C18O appear to be depleted from the gas phase by amounts which vary with position.
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  • 35
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    Physics and chemistry of minerals 26 (1998), S. 14-30 
    ISSN: 1432-2021
    Keywords: Key words ab initio ; NMR ; silicates ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  In order to gain insight into the correlations between 29Si, 17O and 1H NMR properties (chemical shift and quadrupolar coupling parameters) and local structures in silicates, ab initio self-consistent field Hartree-Fock molecular orbital calculations have been carried out on silicate clusters of various polymerizations and intertetrahedral (Si-O-Si) angles. These include Si(OH)4 monomers (isolated as well as interacting), Si2O(OH)6 dimers (C2 symmetry) with the Si-O-Si angle fixed at 5° intervals from 120° to 180°, Si3O2(OH)8 linear trimers (C2 symmetry) with varying Si-O-Si angles, Si3O3(OH)6 three-membered rings (D3 and C1 symmetries), Si4O4(OH)8 four-membered ring (C4 symmetry) and Si8O12(OH)8 octamer (D4 symmetry). The calculated 29Si, 17O and 1H isotropic chemical shifts (δi Si, δi O and δi H) for these clusters are all close to experimental NMR data for similar local structures in crystalline silicates. The calculated 17O quadrupolar coupling constants (QCC) of the bridging oxygens (Si-O-Si) are also in good agreement with experimental data. The calculated 17O QCC of silanols (Si-O-H) are much larger than those of the bridging oxygens, but unfortunately there are no experimental data for similar groups in well-characterized crystalline phases for comparison. There is a good correlation between δi Si and the mean Si-O-Si angle for both Q 1 and Q 2, where Q n denotes Si with n other tetrahedral Si next-nearest neighbors. Both the δ i O and the 17O electric field gradient asymmetry parameter, η of the bridging oxygens have been found to depend strongly on the O site symmetry, in addition to the Si-O-Si angle. On the other hand, the 17O QCC seems to be influenced little by structural parameters other than the Si-O-Si angle, and is thus expected to be the most reliable 17O NMR parameter that can be used to decipher Si-O-Si angle distribution information. Both the 17O QCC and the 2H QCC of silanols decrease with decreasing length of hydrogen bond to a second O atom (Si-O-H···O), and the δ i H increase with the same parameter.
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  • 36
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    Journal of applied spectroscopy 67 (2000), S. 796-805 
    ISSN: 1573-8647
    Keywords: porphyrins ; resonance RS ; nitro-substitution ; structure ; conjugation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The resonance Raman scattering (RS) spectra of a series of nitro-substituted derivatives of the free base of tetraphenyl porphyrin that were obtained on continuous excitation near the Soret band have been investigated. For the molecules in which the NO2 group is located in the β-position of pyrrole rings or in the para-position of meso-phenyl substituents, an intense line of the mode within the range 1340–1355 cm−1 is discovered. Based on the obtained resonance RS spectra of the diprotonated derivatives of nitro-tetraarylporphyrins, it is assigned to symmetrical vibration of a nitro group (ν s NO2). Activation of the ν s NO2 vibration is indicative of the existence of the π-delocalization effect for a number of nitro-substituted porphyrins at which interaction between the molecular orbitals of the nitro-substituents and the porphyrin macrocycle occurs. Moreover, the π-delocalization is typical of both direct addition of a nitro-substituent to the porphyrin ring and of its binding via a meso-phenyl group. The results obtained demonstrate the informative value of the resonance RS spectroscopy for creating and studying model donor–acceptor systems with the participation of porphyrins.
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  • 37
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    Earth, moon and planets 88 (2000), S. 35-58 
    ISSN: 1573-0794
    Keywords: Chemistry ; interplanetary dust particles (IDPs) ; Leonids ; meteor trails ; meteoroids ; meteors ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The cometary Leonid meteoroids represent a size range in between largest carbon-richIDPs and the smallest CI meteorites. Their dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies ofaggregate and cluster IDPs. The Leonid shower meteoroids of known ``comet ejection''ages provide an opportunity to study space weathering of cometary dust over periodsof up to several hundred years. The meteors and aggregate and cluster IDPs displaycontinuous thermal modification of organics and volatile element (Na, K-bearing phases), that occur as discrete minerals and amorphous solids each different response during kinetically controlled ablation. Leonid meteoroids are not excessively Na-rich. The occurrences of Leonid meteors can now be accurate predicted and combined withknowledge better models for the settling rates, collections of surviving dust becomea comet nucleus-sampling mission.
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  • 38
    ISSN: 1435-1528
    Keywords: Key words Vectra B950 ; thermotropic LCP ; rheology ; structure ; orientation ; transients ; dynamic moduli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The structure changes in the start-up flow of the thermotropic liquid crystalline polymer Vectra B950 are probed by performing transient experiments after various flow histories. The shear and normal stress growth curves of a squeezed sample and of a randomly oriented sample show a pronounced overshoot at low strains, whereas the stress growth curve of a sample pre-sheared until steady state shows a gradual increase. This first peak is associated with the re-orientation of the director into the shearing plane. All stress transients show a second broad maximum at large strains that results from the generation of a steady defect network. The effect of varying the relaxation period after pre-shearing is reflected in the appearance of two peaks in the subsequent stress growth curves. One of these peaks shifts linearly with relaxation period and the other is more or less fixed in position. The orientation of the molecules during steady shear flow is on average in the flow direction. Intermediate orientation levels may exist in the transient depending on the amount of strain. The material is able to maintain the flow-induced orientation distribution for a long time after cessation of flow. This is reflected in a similar fashion in the initial magnitudes of the stresses and the dynamic moduli after various preshear strains. Moreover, the dynamic moduli decrease with time after cessation of steady shear flow, indicating that the orientation increases during relaxation.
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  • 39
    ISSN: 1435-1528
    Keywords: Key words Electrorheology ; LCP/DMS blend ; slipping ; structure ; phase structure change ; direct observation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The mechanism of the electrorheological (ER) effect in two types of liquid crystalline polymer (LCP)/dimethylsiloxane (DMS) blends was investigated by rheological measurements and by structure observation under electric field and shear flow. The results show that the phase structures of these immiscible blends can be categorized into slipping (low viscosity) and non-slipping (high viscosity) states. In the non-slipping state, higher viscosity LCP domains connect the electrodes. In the slipping state, on the other hand, LCP domains do not connect the electrodes and the shear is mainly confined in the lower viscosity DMS domains. The ER effect (electrically induced viscosity increase) originates from the electrically induced slipping to non-slipping transition. In one of the blends, the ER effect occurs only at high shear rate, since this blend is in non-slipping state even under no field if the shear rate is low.
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  • 40
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    Journal of superconductivity 11 (1998), S. 95-96 
    ISSN: 1572-9605
    Keywords: Tl-based superconductors ; fluorine ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Fluorine was found to affect the phase formation and superconducting properties of Tl-based superconductors. By varying x in (Tl0.5Pb0.5)Sr1.6Ba0.4Ca2Cu3OyFx synthesized superconductors, an increase was found in the transition temperature and critical current density. These improvements in the superconducting properties are discussed in terms of partial substitution of fluorine into the oxygen sites which in turn affects the hole doping in this material. Structure, microstructure and elemental analysis by XRD, SEM and EDX techniques are reported; the latter of which shows the fluorine distribution.
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  • 41
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    Journal of superconductivity 13 (2000), S. 645-651 
    ISSN: 1572-9605
    Keywords: Y0.8Ca0.2Ba1.8Nd0.2Cu3O y cuprate ; structure ; low temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The variation of structure and transport property for the nominal composition of Y0.8Ca0.2Ba1.8Nd0.2Cu3O y (YCBNC) at temperature range of 78 K 〈 T 〈 284 K were studied. YCBNC shows a superconducting transition temperature (zero resistivity) of T c0 ∼ 83 K. There is no phase transition detected in the accuracy of our experiments in the whole temperature range. The dependences of lattice constants upon temperature can be discussed in two temperature regions. The other atomic parameters, or the deduced structural parameters, such as the orthorhombic strain, the lattice strain, some selected bond lengths and bond angles all depend on temperature. The dependences of the atomic structural parameters on temperature indicate that these atomic structural parameters may relate to the superconductivity to some extent.
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  • 42
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    Journal of superconductivity 13 (2000), S. 977-979 
    ISSN: 1572-9605
    Keywords: high-temperature superconductivity ; other cuprates ; effects of material synthesis ; structure ; chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Evidence is reported that Sr2YRu1−u Cu u O6 superconducts with a transition temperature of at least T c ≈ 30 K for u = 0.1, confirming the reports by Wu et al. that this material superconducts despite having no cuprate planes. (Such planes are widely believed to be necessary for high-temperature superconductivity.) Coexisting with the superconductivity, Sr2YRu1−u Cu u O6 exhibits magnetic order due to antiferromagnetic Ru and Cu.
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  • 43
    ISSN: 1572-9605
    Keywords: Thin films ; microwave surface resistance ; perfect ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effect of the structure YBa2Cu3O7-x superconducting thin films on microwave surface resistance was investigated. The electon channeling patterns (ECPs) and X-ray experimental results showed that the microwave surface resistanceR s is strongly correlated with the perfection of the thin films. The films were deposited on LaAlO3(100) and YSZ(100) substrates. For thin film withR s of 280μΩ, the crystallinity of the thin film shown byw-scanning andφ-scanning was excellent and the ECPs were very sharp. For thin film with highR s of 98 mΩ, only bands from the major zone were visible in the ECPs, which suggested poor crystallinity of the film. From this investigation it was shown that the more perfect the thin films, the lower theR s.
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  • 44
    ISSN: 1572-9605
    Keywords: Single crystals ; high pressure synthesis ; structure ; HgBaCaCuO, CaCuO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Single crystals of Hgl-xPbxBa2Can-lCunO2n+2+ς(x=0,0.2,0.5; n=2,3,4,5) and infinite layer CaCuO2 compounds have been grown using a high gas pressure. Resistivity measurements have been performed in fields up to 10 T. The Hg0.8Pb0.2-1234 single crystals of a size up to 0.5×0.5 mm2 have a T c onset of 130 K. Single crystals of CaCuO2 of a size up to 2×1 mm2 have a T c onset between 70 and 100 K. X-ray structural refinements have been performed on the CaCuO2 and HgPb-12(n−1)n single crystals.
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  • 45
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    Journal of statistical physics 92 (1998), S. 891-908 
    ISSN: 1572-9613
    Keywords: Random sequential adsorption ; hard-sphere particles ; gravity ; diffusion ; coverage ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the coverage and structure of a layer of particles deposited on a line after diffusion in a gravitational field. The dynamics of the depositing particles is controlled by the gravity number N G(=πd 4 Δρg/6k B T), where d is the diameter of the particles, Δρ is the density difference between the particles and the solution, g is the acceleration due to gravity, k B is Boltzmann's constant, and T is the temperature. The position-dependent flux of particles in a gap formed by two preadsorbed particles is estimated by superposition of solutions of a steady-state convective diffusion equation for the flux in the presence of a single preadsorbed particle. The saturation coverages are found with a recursion relation and are in good agreement with those obtained from Brownian dynamics simulation. The jamming coverage increases rapidly with increasing particle size, particularly for large values of Δρ. An algorithm is presented to generate adsorbed configurations from which the structure of the deposit is determined.
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  • 46
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    Journal of superconductivity 11 (1998), S. 743-748 
    ISSN: 1572-9605
    Keywords: Nanocrystals ; nanosuperconductor ; structure ; superconductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A nanosuperconductor was prepared and characterized in the present work. The nanosuperconductor consisted of nanocrystals with superconducting transition temperature, T c, of 88 K. Dimension of the nanocrystals is dozens nm in diameter and hundreds nm in length. The compound of the nanocrystals has a formula of Y4Ba8Cu12O27. The structure of the nanocrystals was found to be an orthorhombic perovskite, and the lattice constants were determined as a = 7.634 Å, b = 7.758 Å, and c = 11.654 Å, respectively.
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  • 47
    ISSN: 1572-9605
    Keywords: Superconductivity ; mercury ; chromium ; synthesis ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We report preliminary results concerning the synthesis and structural characterisation of the chromium stabilised 1201 phases: Hg1−xCrxSr2CuO4+δ. A systematic study of the formation of phases in this system has been undertaken, together with a combined powder neutron and synchrotron x-ray diffraction study, to address the issue of chromium clustering and ordering in this system.
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  • 48
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    Journal of superconductivity 9 (1996), S. 493-501 
    ISSN: 1572-9605
    Keywords: Anisotropy ; phonon dispersion ; symmetry ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The influence of the superconducting gap anisotropy on the phonon dispersion is discussed for tetragonal and orthorhombic crystals. Superconducting order parameters with different types ofs-wave, as well asd- and (s+d)-wave anisotropies, are studied. We show that along specific directions of the Brillouin zone the lineshape (energy and linewidth) of phonons strongly depends on the anisotropy of the gap. In this context, we discuss recent experimental results performed on YBa2Cu3O7 single crystals. The data can be well described in terms of an anisotropics-wave gap function obtained from the nontotally screened interaction of charge carriers with long-range optical phonons. The calculations suggest, furthermore, that it is generally insufficient to describe experiments that involve the anisotropy of the superconducting order parameter solely in terms of its symmetry. Not only the symmetry, but also the specific structure of the gap as a function of k is important. This conclusion holds for those experiments that are not restricted to the pure determination of the phase of the gap.
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  • 49
    ISSN: 1572-9613
    Keywords: associating fluids ; directional bonding ; structure ; local density distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two models have been used in these Monte Carlo simulations: the original model with an angular-dependent associative interaction and a model with an angular-averaged potential, which is better suited for simulation and computationaly more efficient. We show that in the homogeneous case under the same conditions, both models yield a nearly identical interparticle structure, but with a slightly different degree of dimerization. This causes differences between these models in the local density distribution of monomers and dimers when an inhomogeneity is present, though the resulting local total density distribution is found to be the same. The theoretical predictions based on Wertheim's theory of association are always closer to the simulation data for the model with the angular-averaged potential.
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  • 50
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    Studia geophysica et geodaetica 40 (1996), S. 1-8 
    ISSN: 1573-1626
    Keywords: Sun ; structure ; gravitational energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The gravitational potential energy of the Sun and its corresponding internal energy have been estimated on the basis of the standard model of the Sun's internal structure. It is demonstrated that the principal moment of inertia of the Sun, computed from the model, does not fit the hydrostatic equilibrium limit.
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  • 51
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    Hyperfine interactions 128 (2000), S. 375-380 
    ISSN: 1572-9540
    Keywords: low‐alloy steel ; structure ; Mössbauer spectrometry ; X‐rays ; SEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Structural analyses of Fe-Cr and Fe-Cr-Ni low‐alloyed steels before and after annealing at 600○C using Mössbauer spectrometry, X‐ray diffraction and scanning electron microscopy are reported. At the received state, the two steels present a fine bainitic microstructure with equal hardness. From Mössbauer analysis, two iron sites are identified as substitutional by Cr, Mo, Ni atoms and as insertional by carbon in bainitic ferrite. Both sites are locally deformed by residual stresses. The presence of small quantities of retained austenite and ε carbide has been observed. Annealing for one hour at 600○C causes a decrease in hardness for both steels with a decrease of retained austenite. After longer time of annealing, precipitation of (Fe,Ni)23C6 occurs in the Fe-Cr-Ni steel and increases hardness.
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  • 52
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    Applied mathematics and mechanics 21 (2000), S. 19-26 
    ISSN: 1573-2754
    Keywords: structure ; optimization ; topology optimization ; modeling ; dual programming ; O223 ; TU323
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract Topology optimization design of continuum structures that can take account of stress and displacement constraints simultaneously is difficult to solve at present. The main obstacle lies in that, the explicit function expressions between topological variables and stress or displacement constraints can not be obtained using homogenization method or variable density method. Furthermore, large quantities of design variables in the problem make it hard to deal with by the formal mathematical programming approach. In this paper, a smooth model of topology optimization for continuum structures is established which has weight objective considering stress and displacement constraints based on the independent-continuous topological variable concept and mapping transformation method proposed by Sui Yunkang and Yang Deqing. Moreover, the approximate, explicit expressions are given between topological variables and stress or displacement constraints. The problem is well solved by using dual programming approach, and the proposed element deletion criterion implements the inversion of topology variables from the discrete to the continuous. Numerical examples verify the validity of proposed method.
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  • 53
    ISSN: 1573-2746
    Keywords: polycrystal ; ionic ; oxide ; molecular-dynamics ; simulation ; growth ; thin film ; structure ; characterization ; grain boundary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A simulation methodology for the synthesis of polycrystalline, ionic thin films is developed. The method involves the preparation of a polycrystalline substrate onto which a thin film is subsequently grown by crystallization from the melt. A detailed structural analysis of a textured sixteen-grain FeO film, with a grain size of approximately 4.7 nm, shows that the interiors of the grains are almost perfect single crystals with only a very few vacancies and no interstitials. The grains are delineated by 〈001〉 tilt grain boundaries; as expected, the low-angle grain boundaries in the film consist of arrays of dislocations, while the high-angle grain boundaries are relatively narrow and well ordered.
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  • 54
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    Interface science 7 (1999), S. 251-271 
    ISSN: 1573-2746
    Keywords: triple junctions ; taxonomy ; dimensionality ; structure ; energy ; segregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We provide an overview of the properties of triple junctions and quadruple points. It is shown that these junctions may exhibit distinct behaviors that imply that they have and thermodynamically distinct properties in the same way that grain boundaries can be considered as thermodynamically distinct phases, separate from the material that they inhabit. It is shown that the treatment of triple junctions as thermodynamically distinct defects is a natural extension of the treatment of grain boundaries, and that it can be further extended to other junctions such as quadruple nodes. Equilibrium dihedral angles under conditions of anisotropic interfacial energy are explored, and it is found that the dihedral angles may be variable under a range of different conditions.
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