Refinement of the crystal structure of sanidine-like feldspar

The crystal structure of sanidine-like feldspar of the composition KAlSi₃O₈ from the Khibiny alkaline massif (the Kola Peninsula) has been refined (X-ray diffraction analysis; automated Syntex $P\bar 1$ diffractometer; 2θ: θ scanning technique; 2320 reflections; R _(hkl) = 0.0409; anisotropic refinement; AREN program package). The data obtained for KAlSi₃O₈ are: a = 8.615(9), b = 13.030(7), c = 7.200(5) Å, α = 89.99(5)°, β = 116.01(6)°, γ = 89.98(7)°, Z = 4, sp. gr. $C\bar 1$ . Microtwinning revealed in the crystal structure of the mineral explains the simultaneous existence of two structural-optical types in one sample—“high” and “low” sanidines.     

Crystal structure of tisinalite Na2(Mn,Ca)1 − x (Ti,Zr,Nb,Fe3+)[Si6O8(O,OH)10]

Crystal structure of tisinalite from the Lovozero alkaline massif (the Kola Peninsula) was established by single-crystal X-ray diffraction analysis (SYNTEX $\bar P1$ diffractometer, λMoK_α radiation, 2θ/θ scanning mode). The structure solution (SHELX97 program package, R _hkl = 0.0565, 951 independent reflections, anisotropic refinement of thermal atomic displacements) confirmed that tisinalite belongs to the lovozerite structure type (sp. gr., $\bar P1$ , a = 10.036(5) Å, c = 12.876(9) Å, Z = 3). The difference between the structure of tisinalite and the structures of the minerals of the lovozerite group established earlier consists in the nature of the occupancy of both cation and anion positions.     

Structure of a liquid crystal of 4-cyano-4′-n-octyloxybiphenyl

The structure of a liquid crystal of 4-cyano-4′-n-octyloxybiphenyl (C₂₁H₂₅NO) is determined by X-ray diffraction analysis. The compound crystallizes in the triclinic crystal system with unit cell parameters a = 7.322(1) Å, b = 12.693(3) Å, c = 20.393(2) Å, α = 92.45(1)°, β = 99.96(1)°, γ = 99.35(2)°, and space group $P\bar 1$ . The structure is solved by the direct method and refined to R = 0.057. Two independent molecules are located in the asymmetric unit. No short intermolecular contacts are observed in the crystal packing.     

Peculiar reflections in diffraction patterns as indicators of structural type and quality

Reflections serving as indicators of the types of packets forming crystal structures of many layered semiconductors have been revealed in diffraction patterns. It is found that the values l for the strongest reflection in series 000l and 00l, as well as the next to the strongest reflection in series \(hh\bar 2\bar hl\) (h = const) and 0kl (k = const) for hexagonal and monoclinic structures, respectively, determine the number of polyhedral (Tand O) cation-filled layers per cell and indicate the types of packets TOT \(TO\bar TE\) , \(TO\bar T\bar TE\) , \(TOO\bar TE\) , \(TTO\bar T\bar TE\) , \(OOE_1 TO\bar TE_1 \) and OOE \(OOE_1 TO\bar TE_2 TO\bar TE_1 \) , where T and \(\bar T\) are inversely oriented tetrahedra, O is an octahedron, E is an empty interpacket layer, and E₁ and E₂ are partially filled (to less than 1/3) interpacket layers.     

Reaction of 2,3-bis(diphenylphosphino)maleic acid-thioanhydride (bmata) with PhCCo3(CO)9. X-ray diffraction structure of {\text{Co}}_{\text{3}} ({\text{CO)}}_{\text{6}} [\mu _2 ,\eta ^2 ,\eta ^1 {\text{ - C(Ph)}}{\text{(O)](}}\mu _2 {\text{ - PPh}}_{\text{2}} )

The benzylidyne-capped cluster PhCCo₃(CO)₉ (1) reacts with the diphosphine ligand 2,3-bis(diphenylphosphino)maleic acid-thioanhydride (bmata) to afford ultimately the new cluster ${\text{Co}}_{\text{3}} ({\text{CO)}}_{\text{6}} [\mu _2 ,\eta ^2 ,\eta ^1 {\text{ - C(Ph)}}{\text{(O)](}}\mu _2 {\text{ - PPh}}_{\text{2}} )$ (3) in low yield under thermolysis conditions or by Me₃NO activation of PhCCo₃(CO)₉. The intermediate cluster compound PhCCo₃(CO)₇(bmata) (2) has been confirmed by IR spectroscopy and is shown to give ${\text{Co}}_{\text{3}} ({\text{CO)}}_{\text{6}} [\mu _2 ,\eta ^2 ,\eta ^1 {\text{ - C(Ph)}}{\text{(O)](}}\mu _2 {\text{ - PPh}}_{\text{2}} )$ upon heating. Cluster 3 has been isolated and characterized in solution by IR and ³¹P NMR spectroscopies, and the solid-state structure of 3 was established by X-ray diffraction analysis. ${\text{Co}}_{\text{3}} ({\text{CO)}}_{\text{6}} [\mu _2 ,\eta ^2 ,\eta ^1 {\text{ - C(Ph)}}{\text{(O)](}}\mu _2 {\text{ - PPh}}_{\text{2}} )$ crystallizes in the triclinic space group P ${\bar 1}$ , a = 11.6053(8) Å, b = 11.8438(8) Å, c = 15.099(1) Å, α = 105.169(5)^○, β = 90.530(5)^○, γ = 104.976(6)^○, V = 1928.5(2) ų, Z = 2, and d _calc = 1.578; R = 0.0442, R _w = 0.481 for 2591 observed reflections with I > 3σ (I). The cyclic voltammetric properties of 3 have been investigated and are contrasted with the related bma-derived cluster ${\text{Co}}_{\text{3}} ({\text{CO)}}_{\text{6}} [\mu _2 ,\eta ^2 ,\eta ^1 {\text{ - }}{\text{(O)OC(O)](}}\mu _2 {\text{ - PPh}}_{\text{2}} )$ .     

Carbon–hydrogen and carbon–phosphorus bond cleavage in a triruthenium cluster complex containing dppm: The crystal and molecular structures of Ru3(CO)6{μ 3-OPPh2 C2H(C6H4)PPhCH2PPh}(μ 3-OPPh2)Ph and Ru3(CO)6 {μ-OPPh2C2H(C6H4)PPhO}(μ-PPh2)(μ-PPh2O)

The crystal and molecular structures of Ru₃(CO)₆{μ ₃-OPPh₂C₂H(C₆H₄)PPhCH₂PPh}-(μ ₃-OPPh₂)Ph (1) and Ru₃(CO)₆{μ-OPPh₂C₂H(C₆H₄)PPhO}(μ-PPh₂)(μ-PPh₂O) (2) have been determined by single crystal X-ray diffraction. Both complexes contain oxygen atoms oxidatively inserted into phosphorus–ruthenium bonds, and unique σ/π multidentate ligands formed from C $---{\text{H}}$ H and C $--$ P bond cleavage in bis(diphenylphosphino)acetylene and bis(diphenylphosphino)methane. Complex 1 crystallized in the triclinic space group ${\bar 1}$ , with lattice parameters a = 11.642(4) Å, b = 15.018(5) Å, c =16.587(5) Å, α = 2.48(3)°, β = 76.47(2)°, γ = 70.35(3)°, V = 2651.1(15) ų, Z = 2. Complex 2 crystallized in the centered monoclinic space group, C2/c, with lattice parameters a = 34.467(4) Å, b = 14.274(2) Å, c = 23.258(3) Å, β = 5.29(1)°, V = 11394(3) ų, Z = 8.     

Anisotropy of microhardness of β-BaB2O4 single crystals

The anisotropy of microhardness of β-barium borate single crystals β-BaB₂O₄ (BBO) is studied by the sclerometry method on the (0001) basal plane, the $(10\bar 10)$ plane of the hexagonal prism, and the $(11\bar 20)$ plane of the trigonal prism. It is shown that the anisotropy observed in the crystal is determined by the directions of covalent B-O bonds. It is established that the anisotropy of microhardness correlates with the system of cleavage planes.     

Kinetics of hydrothermal crystallization of quartz in Na2CO3 solutions

The kinetics of crystallization of the {0001}c, {01 $\bar 1$ 1}r, and {10 $\bar 1$ 1}R faces of quartz in 0.5 M Na₂CO₃ (M is molarity) aqueous solutions has been studied in the temperature range 200–450°C. It is established that the dependence of the crystal growth rate on temperature in the logV-1/T, K coordinates is of a parabolic nature. It is most probable that the nonlinearity of this dependence is associated with a deficiency in the solution of silica monomers, taking part in the elementary event of quartz crystallization. The causes of a jumpwise decrease in the activation energy of the growth of the c, r, and R faces at t > 280–325°C are considered.     

Preparation and crystal structure of the new ionic bis-[hydrazido]-molybdenum complex [Mo(NNPh2)2(acac)(PPh3)2]+OTf−

The title compound [Mo(NNPh₂)₂ (acac)(PPH₃)₂]⁺OTf^?, Mr=1233.1, crystallizes in the triclinic space group $P\bar 1$ , witha=12.881 (4),b=13.795(3),c=17.160(5)Å, α=90.95(1), β=91.31(1), ψ=103.53(1)°, andZ=2. The structure was solved by Patterson methods, and refined with some difficulties due to extensive disorder in the counterion. The Mo ion is hexacoordinated in an octahedral environment, with two O and two N defining the basal plane, and two P atoms in the apical sites.     

Flexoelectric effect and statistical properties in polar liquid crystals

The structural properties and flexoelectric coefficients e ₁ and e ₃ of polar liquid crystals (LCs) such as 4-n-pentyl-4′-cyanobiphenyl (5CB) are studied in the nematic phase by the molecular-dynamics and statistical-mechanics methods. A number of order parameters, $\bar P_{2L} (L = 1,2,3)$ and $\bar P_2 (r)$ , and orientational correlations ξ_λ for the nearest and next-nearest neighbors were investigated. The calculations show the absence of spontaneous polarization $(\bar P_1 \simeq 0)$ in the nondeformed polar 5CB liquid crystal over the entire range of temperatures corresponding to the nematic phase. The origination of spontaneous polarization (characterized by two independent flexoelectric coefficients e ₁ and e ₃) in response to an external deformation of a 5CB sample is studied. The calculated e ₁ and e ₃ coefficients agree well with the experimental data for 5CB obtained by the pyroelectric method.     

Program for calculating the scattering parameters used in the X-ray standing wave method

A computer program for calculating the complex kinematic scattering parameters χ₀, χ_h, and $\chi _{\bar h} $ of X rays, which are Fourier components of the crystal complex susceptibility, as well as some of their combinations, is presented. The values calculated by the program can be used for computer simulation of experimental results obtained by the X-ray standing-wave method. Methods for calculating these parameters on the basis of well-known tables are described in detail. For crystals of complex structure, it is necessary to know their structure and the Debye temperature or specific heat capacity in order to calculate χ_h and $\chi _{\bar h} $ . To calculate χ₀, it is sufficient to know the chemical formula and the density of a material.     

Formation of zinc oxide quasibicrystal structures

Quasibicrystal structures with interblock boundaries of epitaxial zinc oxide layers on a sapphire substrate along a given direction have been obtained for producing submicron electronic devices. It is shown that the use of the buffer technique allows one to grow on one (10 $\bar 1$ 2) α-Al₂O₃ substrate ZnO layers oriented in the (11 $\bar 2$ 0)and (0001) planes with clearly pronounced interlayer boundaries. The morphology and structural characteristics of these layers are studied.     

Ba1−x R x F2 + x Phases (R = Gd-Lu) with distorted fluorite-type structures—products of crystallization of incongruent melts in the BaF2-RF3 Systems (R = Gd-Lu). III. Defect Ba0.75Lu0.25F2.25 structure. A new {Lu8[Ba6F71]} supercluster of defects

The structure of Ba_0.75Lu_0.25F_2.25 crystals grown from melt has been studied by X-ray diffraction analysis (4729 measured reflections, 269 independent reflections with I > σ (I), R = 1.1%, R _w = 0.7%). The crystals are crystallized in the cubic system, sp. gr. Pm $\bar 3$ m, with the lattice parameter a = 5.9870(9) Å. A new complex of defects is singled out—a supercluster of the composition {R ₈[Ba₆F₇₁]}. This supercluster differs from the well-known rare earth octahedral supercluster of the composition {Ba₈[R ₆F_68-69]} because its nucleus is formed not by RE cations but by an alkali earth cation, Ba. The {R ₈[Ba₆F₇₁]} supercluster has a configuration close to that of the [B₁₄F₆₄] fragment of the fluorite structure and can replace the latter isomorphously. The model of the Ba_0.75Lu_0.25F_2.25 crystals consisting of coherently intergrown isostructural microphases having different chemical compositions is characterized by the good agreement of the calculated and experimentally determined occupancies of the F^1? positions. The comparison of the Ba_0.8Yb_0.2F_2.2 (phase studied earlier) and Ba_0.75Lu_0.25F_2.25 structures demonstrates the evolution of the defect structure along the series of rare earths with the corresponding change of the sp. gr. Fm $\bar 3$ m by the sp. gr. Pm $\bar 3$ m.     

Molecular and crystal structure of the echinochrome complex with dioxane

The molecular and crystal structures of a complex of echinochrome (2,3,5,6,8-pentahydroxy-7-ethyl-1,4-naphthoquinone) with dioxane are determined. The molecular complex 2(C₁₂H₁₀O₇) · C₄H₈O₂ crystallizes in the form of dark red transparent thin plates. The crystal data of the compound are as follows: a = 4.563(1) Å, b = 6.382(1) Å, c = 22.812(4) Å, α = 91.955(5)°, β = 90.408(5)°, γ = 104.801(4)°, space group $P\overline 1 $ , and Z = 2. The crystal structure is solved by direct methods and refined to R ₁ = 0.0656 and wR ₂ = 0.1196.     

Regular domain structure in a lithium niobate crystal—Period stabilization

High stability of the period and homogeneity of a regular domain structure was attained in Nd: Mg: LiNbO₃ crystals grown from melt with an excess of lithium oxide by the Czochralski method along the normal to the close-packed $\{ 01\bar 12\} $ face.     

Crystal and molecular structure of the 1: 1 molecular complex between 1e-benzyl-3e-hydroxy-3a-methyl-4a-tosylhydrazo-6e-phenylpiperidine-4e-carbonitrile and diethyl ether

The crystal and molecular structure of the 1: 1 complex between 1e-benzyl-3e-hydroxy-3a-methyl-4a-tosylhydrazo-6e-phenylpiperidine-4e-carbonitrile and diethyl ether is studied by X-ray diffraction (Nicolet R3m diffractometer, MoK _α radiation, ? /2? scan mode). The crystals are triclinic, space group $P\bar 1$ , a = 10.547(4) Å, b = 12.382(5) Å, c = 13.487(6) Å, α = 114.79(3)°, β = 97.28(3)°, γ = 98.40(3)°, and Z = 2. The structure is solved by the direct method and refined to R = 0.0605. Molecular structures and hydrogen bonds are discussed.     

Polytypism and superstructure in CoInGaS4

It is established that a one-layer polytype 1T with the unit-cell parameters a = 3.758, c = 12.135 Å, sp. gr. P3m1 and the structure module _hT_hO_hT_hE is mixed with the three-layer polytype 3R with the unit-cell parameters a = 3.758, c = 36.405 Å, sp. gr. R3m and the structure module _hT_cO_cT_hE, where T and O are two-dimensional nets of tetrahedra and octahedra, respectively, E is the empty intermediate layer, and h and c indicate the hexagonal and cubic packings of atomic planes S. The microdiffraction pattern in the hexagonal basis shows a monoclinic superlattice with the parameters $A = \sqrt {19} a, B = \sqrt {13} a, \gamma = 110.485^\circ$ related to the main hexagonal lattice as A = [520] and $B = [\bar 130]$ .     

Crystal structure analysis of (Morpholino)(Phenyl)(Dicyclohexylamino) phosphiniminocyclotrithiazene

The title compound (C₆H₅)(C₄H₈NO)[N(C₆H₁₁)₂]P=N-S₃N₃ crystallizes in a triclinic crystal system with unit cell parameters a = 9.8884(4) Å, b = 10.6075(1) Å, c = 14.2276(2) Å, α = 78.14(3)°, β = 79.31(1)°, λ = 65.42(2)°, V = 1319.44(6) ų, Z = 2, and space group $P\bar 1$ . The cyclotrithiazene ring adopts a “distorted chair” conformation with a deviation of 0.682(7) Å for the tricoordinated sulfur atom. Remarkably, a short exocyclic S-N bond length 1.489(4) Å along with a large P-N-S angle 136.2(3)° are observed with the iminophosphorus moiety.     

Crystal structure of 2,4′-biflavonoid

The X-ray crystal structure of 2,4′-biflavonoid has been determined. Colorless regular prism shaped crystals of C₃₀H₂₂O₄ crystallize in the space group $P\bar 1$ with cell dimensionsa=11.574(1) Å,b=12.235(1) Å,c=17.428(1) Å, α=108.46(3)^o, β=80.08(1)^o, γ=103.34(2)^o,V=2264.7(4) ų, andZ=4.     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.