On the theory of steady state lamellar eutectic solidification at high solidification rates

The famous theory of JACKSON and HUNT for the unidirectional eutectic solidification is extended considering the effect of the solidification rate on the interfacial solute concentration. Contributions attributed to nonsymmetric phase diagrams lead to corrections of the constant K in the λ²V = K relation between the lamellar half-spacing λ and the solidification rate V. For high solidification rates deviations from this relation are derived.     

On the morphology of <100>-textured Germanium Crystallites in Zn—Ge Eutectic Alloy

Different geometry parameters for the cross-like germanium crystallites (eutectic dendrites) of the Zn-Ge eutectic alloys unidirectionally solidified have been related to the growth rate R and liquid temperature gradient G using linear regression analysis. It has been found that for eutectic dendrite spacing λ, balk length d and balk thickness b follow the relationship of the type w = C_wR^−rwG^−gw; C_w is a constant. The spacing relationship of eutectic dendrites (r_λ = 0.21; g_λ = 0.48) shows a similarity with published experimental and theoretical results on primary dendrite arm spacing (r_λ = 0.25; g_λ = 0.5). It has been shown in terms of a profile ration λ/d that for geometrical similar morphologies the relationship λ²R = const. is valid.     

Structure of monoclinic acridine orange hydrochloride monohydrate,C17H19N3 · HCl · H2O

M_r = 319.82, monoclinic P2₁/a, Z = 4, a = 14.545(5), b = 15.562(6), c = 8.538(4) Å, β = 120.66(3)°, V = 1662(1) ų, D_m = 1.27 Mgm⁻³, D_x = 1.278 Mgm⁻³, λ(MoKα) = 0.71069 Å, μ(MoKα) = 0.24 mm⁻¹, T = 297 K. Final R = 0.049 for 1485 observed reflections. All hydrogen atoms were located and refined isotropically. Bond lengths (σ = 0.004 Å) and angles (σ = 0.3°) are normal. The substance is a derivative of acridine. The structure consists of chloride anions, bisdimethylaminoacridinium cations and water molecules. In the solid state the molecules are approximately planar. Pairs of cations form dimers with parallel planes connected by an I inversion centre and plane distances of 3.474 Å. They overlap with partial areas of all three six membered rings.     

Structures of the Triclinic and the Monoclinic Modification of Divascan®

Trielinic modification: C₁₂N₄O₃H₁₆. Mr = 264.26, triclinic P 1 , a = 7.702(3), b = 9.420(11),c = 10.893(8) A, α = 73.37(8), β = 82.22(5), γ = 66.30(6)°, V = 638(1) A³, Z = 2, D_m = 1.360 Mg m⁻³, D_x = 1.362 Mg m⁻³, λ(MoK_α) = 0,71062 A, μ = 0.1084 mm⁻¹, F(000) = 280, T = 296 K, final R = 0.0742, wR = 0.0758 for 1842 reflections. Monoclinic modification: C₁₂N₄O₃H₁₆·, 3/2H₂O, M_r = 291.28, monoclinic P 2₁,/c, α = 14.075(5), b = 12.631(6), c = 16.234(5) A, β = 99.25(3)°, V = 2849(1) A³,Z = 8, D_m = 1.338 Mg m⁻³, D_m = 1.359 Mg m⁻³, λ(MoK_α) = 0.71062 A, μ = 0.1134 mm⁻¹, F(000) = 1240, T = 296 K, final R = 0.0557, wR = 0.0691 for 1266 reflections. Comparison of the two independent Divascan® molecules of the monoclinic modification with the one of the triclinic modification demonstrates good agreement of related bond distances and angles in the molecules. Disorder of the hydroxyl groups of one Divascan® molecule of the monoclinic modification is announced by high vibration parameters of the related oxygen atom and a very short C O distance, which is not adequate to a real C O bond length.     

Synthesis and Structure of Ba<Subscript>5</Subscript>(V<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>

Abstract  A new barium chlorovanadate, Ba₅(V₂O₇)₂Cl₂, was isolated by a high-temperature (850 °C) reaction employing a CsCl/RbCl flux. The structure was determined by single crystal X-ray diffraction methods. This compound crystallizes in an orthorhombic crystal system, Pmmn (No. 59), with a = 11.558(2) ?, b = 15.164(3) ?, c = 10.023(2) ?, Z = 4 and V = 1756.7(6) ?³. The structure of Ba₅(V₂O₇)₂Cl₂ was determined by full-matrix, least-squares methods with R ₁ = 0.0398, wR ₂ = 0.1069 and GOF = 1.048 for all data. This new structure can be described as a composite lattice made up of mixed covalent and ionic moities. The extended framework is orchestrated by stacked [Ba(V₂O₇)Cl]³⁻ slabs that are interconnected by Ba²⁺ cations through Ba–O bonds to the [V₂O₇] units. The Ba²⁺ and Cl^- ions form BN-type “[BaCl]” sheets with pseudo-hexagonal windows that are centered by [V₂O₇]⁴⁻ pyrovanadate units. Graphical Abstract  The structure of a new chlorovanadate, Ba₅(V₂O₇)₂Cl₂, exhibits an interesting BN-type salt lattice that consists of an extended [BaCl] sheet containing pseudo-hexagonal windows that are centered by [V₂O₇] pyrovanadate units.      

Structure refinement with X-ray powder diffraction data for synthetic calcium hydroxyapatite by Rietveld method

Ca₅(PO₄)₃OH, M_r = 502.3, hexagonal, P 6₃/m, a = 9.4207(3), c = 6.8780(2) Å, V = 528.67 ų, Z = 2, D_x = 3.156 Mg · m⁻³, CuKα, λKα₁ = 1.54051, λKα₂ = 1.54433 Å, μ = 26.25 mm⁻¹, F(000) = 500, T = 294 K. The powder diffraction pattern was analysed by the Rietveld method. The parameters were refined by the program PFSR (DBW2.9) to final R-factors R_p = 0.079, R_wp = 0.081 and R_B = 0.015.     

Crystal and molecular structure of 1-diazo-2,3,4,5-tetraphenylcyclopentadiene

M_r = 396.30, monoclinic space group P 2₁/c, a = 10.145(2), b = 18.523(4), c = 12.443(2) Å, β = 110.31(2)°, V = 2193(1) ų, Z = 4, D_x = 1.201 Mg m⁻³, F(000) = 832, λ(MoKα) = 0.71069 Å, μ = 0.7 mm⁻¹. The crystal structure was determined by direct methods and refined by least-squares procedure to the discrepancy factor R = 0.039.     

Crystal and molecular structure of 1-(p-nitrophenyl)-2-acetylamino-3-brom-propen-2-on-1, C11H9BrN2O4

M_r = 313.11, orthorhombic space group Pbca, a = 8.165(1), b = 9.491(2), c = 32.207(5) Å V = 2496(1) ų, D_X = 1.667 Mgm⁻³, Z = 8, F(000) = 1248, λ(MoKα) = 0.71069 Å, μ = 32.7 mm⁻¹. The crystal structure was determined by direct methods and refined by least-squares procedure to the discrepancy factor R = 0.065. Positions of hydrogen atoms were calculated. The structure determined by x-ray analysis confirms the chemical results.     

Crystal and molecular structure of 5-diazo-2,2-dimethyl-4,6-dioxo-1,3-dioxane and 5-diazo-1,3-dimethylpyrimidin-2,4,6-trione

C₆N₂O₄H₆: M_r = 170.12, orthorhombic space group Pbca, a = 6.751(2), b = 13.669(4), c = = 16.845(4) Å, V = 1555(1) ų, D_x = 1.248 Mgm⁻³, Z = 8, F(000) = 704, λ(moKα) = 0.71069 Å, μ = 1.1 mm⁻¹. The crystal structure was determined by direct methods and refined by least-squares procedure to the discrepancy factor R = 0.039. C₆N₄O₃H₆: M_r = 182.14, monoclinic space group C2/c, a = 17.726(8), b = 6.191(12), c = 16.062(6) Å, β = 117.59 (3)°, V = 1562 (1) ų, D_x = 1.549 Mgm⁻³, Z = 8, F(000) = 752, λ(MoKα) = 0.71069 Å, μ = 1.2 mm⁻¹. The crystal structure was determined by direct methods and refined by least-squares procedure to the discrepancy factor R = 0.056.     

Role of oxygen vacancies in the origin of ferromagnetism in Mn‐doped ZnO

The relationship between the oxygen vacancy and ferromagnetism in Mn‐doped ZnO has been studied based on the first‐principles calculations. Three possible charge states of oxygen vacancies, i.e., neutral (V_O⁰), 1+ (V_O¹⁺) and 2+ (V_O²⁺) are considered. Results show that the lattice relaxations around oxygen vacancies are large difference under different charge states. It is found that V_O¹⁺ and V_O²⁺ oxygen vacancies induce ferromagnetism. However, Mn‐doped ZnO system shows ferromagnetism with V_O⁰ oxygen vacancies in hydrogenated environment, the ferromagnetism is attributed to the interstitial H, which forms a bridge bond and mediates d ‐d coupling and stabilizes the ferromagnetic state. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure of phases of the sillenite family in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-V<Subscript>2</Subscript>O<Subscript>5</Subscript> system

X-ray diffraction studies of sillenite Bi₂₄V₂O₄₀ single crystals grown by the hydrothermal method are performed for a separate crystal and powdered crystals. It is found that the composition of the two specimens is described by the (Bi_{24 − x} ▭ _x )[Bi _y ³⁺V_1−y ⁵⁺]₂ O₄₀ general formula with completely populated oxygen sites but differs in the content of vacancies at the bismuth site (this was established for the first time) and the Bi: V ratio at the tetrahedral site. The structural models of all the vanadium-containing sillenites reported in the literature are considered, and the possibility that Bi atoms are located at the centers of BiO₄ tetrahedra is established.     

Crystal structure determination of bis-dimethyl heptamethine cyanine chloride,C11N2H19Cl · 4 H2O

Mr = 286.59, monoclinic superposition structure C 121, Z = 4, a = 15.248(3), b = = 6.942 (3), c = 9.074(1) Å, β = 120.1(1)°, V = 827(1) ų, D_m = 1.13(1) Mg m⁻³, D_x = = 1.15 Mg m⁻³, λ(MoK_α) = 0.71069 Å, μ = 0.243 mm⁻¹, F (000) = 312, T = 296 K, final R = 0.061 for 802 reflections. All hydrogen atoms were located. The structure consists of chloride anions, bis-dimethyl heptamethine cyanine cations and water molecules. The structure of bis-dimethyl heptamethine cyanine chloride is disordered, e.g. there exist partial coincidence operations, leading to more than one stacking mode of the bis-dimethyl heptamethin cyanine chains. The crystal structure consists of rows of molecule along the a-axis. The C C bonds show the bond length compensation, typical of polymethines, towards a partial double bond (mean value 1.38 Å) between formally sp²-hybridized C atoms. The C N bond lengths to the methyl carbon atoms (mean value 1.49 Å) correspond to normal C N single bonds. The valence angles at the C atoms of the heptamethine chain clearly alternate and deviate systematically from 120°. This is also observed in other structures of a similar type. The structure determined by X-ray analysis confirms the chemical results.     

Crystal structure determination of 2-acetylamino-4-benzoyl-5,5-dimethyl-4,5-dihydro-1,3,4-thiadiazolin,C13H15N3O2S

Thiosemicarbazone is receiving increasing interest because of the biological activity of some of its derivatives. Mr = 277.35, space group P2₁2₁2₁, Z = 4, a = 9.290(3), b = = 11.512(2), c = 13.286(2) Å, V = 1421 (1) ų, D_m = 1.29(1) Mg m⁻³, D_x = 1.296 Mg m⁻³, λ(MoK_α) = 0.71062 Å, μ = 0.230 mm⁻¹, F(000) = 584, T = 296 K, final R = 0.028 for 1255 reflections. All hydrogen atoms were located. The structure determed by X-ray analysis confirms the chemical results. The structure analysis of the title compound is described and its molecular and crystal structure discussed.     

Crystal and molecular structure of 2-diazo-5-phenyl-cyclohexan-1,3-dione

M_r = 214.24, monoclinic space group P 2₁, a = 10.964(2), b = 5.870(2), c = 8.574(2) Å, β = 98.09(2)°, V = 546(1) ų, Z = 2, D_x = 1.302 Mg m⁻³, F(000) = 224, λ (MoKα) = 0.71069 Å, μ = 0.8 mm⁻¹. The crystal structure was determined by direct methods and refined by least-squares procedure to the discrepancy factor R = 0.034. M_r = 214.24, monokline Raumgruppe P 2₁, a = 10.964(2), b = 5.870(2), c = 8.574(2) Å, β = 98.09(2)°, V = 546(1) ų, Z = 2, D_x = 1.302 Mg m⁻³, F(000) = 224, λ(MoKα) = 0.71069 Å, μ = 0.8 mm⁻¹.     

Structure of N-5-Anilino-pentadien-(2,4)-ylidenaniliniumperchlorate,C17H17N2O4Cl

M_r=348.65, monoclinic, P2₁/n, a=11.088(2), b=17.521(3), c=8.845(2) Å, β=98.87(3)⁰, Z=4, V=1697.8(8) ų, D_x=1.368(1) Mgm⁻³, μ(MoKα)=0.256 mm⁻¹, λ(MoKα)=0.71069 Å, T=296 K. Final R=0.040 for 2454 independent reflections excluding those with |F₀|<4σ(|F₀|). Intensities were measured with an automatic diffractometer. The structure belongs to the openchained cyanines. Characteristic for this class of compounds is their nearly ideal polymethinic electron structure with its main geometrical features: equalisation of bond lengths, alternation of bond angles, planarity of the polymethinic chain. All three features are significantly to be observed in the structure. The bond angle alternation determines essentially the shape of the molecules and the molecular packing.     

On the Density of Synthetic Glasses in the System Soda Melilite – Gehlenite/Ákermanite

The solid density has been determined at 25°C by hydrostatic weighing along the binary systems Sm–Ge₅₀Åk₅₀ and Sm–Ge₇₀Åk₃₀. The molar volume V decreases linearly with increasing mole fraction of Ge_mÅk_n, x_B, according to δV/δx_B = −5.08 cm³ mol⁻¹ and −4.40 cm³ mol⁻¹ for Ge₅₀Åk₅₀ and Ge₇₀Åk₃₀, respectively. The results enable the molar fraction x_B to be determined from density measurements with an absolute error of ±5 mol%.     

Crystal and molecular structures of N-alkyl-N,N-dimethyl-3-(heptamethyltrisiloxan-3-yl) propylammonium bromides

C₁₆H₄₂NO₂Si₃Br: M_r = 444.76, monoclinic space group P 2₁/c, a = 23.300(8), b = 8.918(4), c = 13.403(2) Å, β = 101.69(4)°, V = 2727(1) ų, D_x = 1.08 Mgm⁻³, D_exp = 1.06 Mgm⁻³, Z = 4, F(000) = 932, λ(MoKα) = 0.71069 Å, μ = 16.3 cm⁻¹. The crystal structure was determined by direct methods and refined by least-squares procedure to the discrepancy factor R = 0.117. C₁₅H₄₀NO₂ Si₃Br: M_r = 430.34, monoclinic space group P2₁/c, a = 23.460(4), b = 8.518(2), c = 13.403(2) Å, β = 102.03(2)°, V = 2619(1) ų, D_x = 1.09 Mgm⁻³, D_exp = 1.07 Mg⁻³, Z = 4, F (000) = 920, λ(MoKα) = 0.71069 Å, μ = 33.9 cm⁻¹. The crystal structure was determined by least-squares refinement of the structure model derived from structure determination of C₁₆H₄₂NO₂·Si₃Br to the discrepancy factor R = 0.099. C₁₆H₄₂NO₂Si₃Br: Daten siehe oben. C₁₅H₄₀NO₂Si₃Br: Daten siehe oben.     

The crystal structure of dodecyltrimethylammoniumbromide

C₁₅H₃₄BrN, monoclinic, P 2₁/m, a = 21.603(9), b = 7.261(3), c = 5.636(2) Å, β = 86.85(2)°, Z = 2, V = 882.72 ų, D_x = 1.160 g/cm³, μ(MoKα) = 2.45 cm⁻¹, λ(MoKα) = 0.71069 Å. The structure of this cationic surfactant was solved with Patterson methods and refined to R = 0.091 for 2057 measured reflections. The dodecyl chains are slightly screwed around their chain axes. The hydrocarbon chains are statistically disordered. The polar regions satisfy the mirror plane which is by remaining parts only statistically fulfilled. In the process of structure refinement statistical disorder has been included by separation of some atom positions. The sublattice of the hydrocarbon chains is nearly O⟂ with a_s = 5.14, b_s = 7.26, c_s = 2.52 Å.     

Crystal structure and electrochemical behavior of a novel polyoxometalate [Ni(bpy)3]2[W4V2O19] with Lindqvist‐type structure

A novel polyoxometalate [Ni(bpy)₃]₂[W₄V₂O₁₉] (Ni₂V₂W₄) has been synthesized by the hydrothermal method and the structure determined by X‐ray crystallography. Ni₂V₂W₄ crystallizes in a trigonal system with space group R ‐3c (a = 15.8984 (5) Å, b = 15.8984 (5) Å, c = 43.855 (3) Å). In the structure of the compound, terminal and bridging oxygen atoms are bond to the metal centers by σ or π bonds. The W⁶⁺ and V⁵⁺ ions in isopolyanion [W₄V₂O₁₉]^4‐ statistically distribute over the six metal centers. Using cathodic adsorptive voltammetric method with a carbon paste electrode, the redox property and the electron transferring process were studied. The results show that electrochemical behavior about W(VI) and V(V) atoms give one‐electron, three‐electron and two‐electron reduction waves. Three successive oxidation waves are observed too. The compound was also characterized by thermal gravimetric analysis and IR spectra. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrical Characterization of Irradiation plus Annealing – induced VAsZnGa Pairs in p-type GaAs (Zn) Crystals

Effect of fast electron irradiation (E =2.2 Mev, ϕ_c = 1 × 10¹⁶ el/cm²) and subsequent annealings (T = 150 to 350 °C, t = 10 to 600 min) of zinc-doped p-type GaAs crystals on the formation and dissociation of V_AsZn_Ga, pairs is studied. An analysis of the formation and dissociation kinetics of V_AsZn_Ga pairs permitted to find the diffusion coefficient of radiation-induced arsenic vacancies D(D = 1.5 × 10⁻¹⁸, 1 × 10⁻¹⁷ and 5 × 10⁻¹⁷ cm²/s at 150, 175 and 200 °C accordingly), their migration energy ϵ_m(ϵ_m = 1.1 eV), the binding energy of V_AsZn_Ga, pairs ϵ_b(ϵ_b = 0.5 eV), and also their dissociation energy ϵ_d(ϵ_d = 1.6 eV).