Phase lead determined growth of 〈100〉 — textured germanium crystallites in eutectic Ag?Ge alloys

Al Si type eutectics (Al Si, Ag Si, Ag Ge, Zn Ge) form 〈100〉 — textured eutectic dendrites of the semiconductor phase when a certain growth rate R and liquid temperature gradient G are held. The spacings of these eutectic dendrites λ follow the relationship: λ = (r_λ ≈︁ 0.2; g ≈︁ 0.5). The exponents of this relationship can be explained by the model of phase lead determined growth. This model is based on the consideration of the analogy to dendrite growth. The Al Si type eutectics have geometrically similar morphologies for determined G^x/R-relations (x = 1.25 in the case of Ag Ge) and the relation λ²R = const. is valid. In this paper the Ag Ge eutectic will be discussed in close detail.     

Interfacial stability and grain diameter of the metal phase of directionally solidified Al-Si-type eutectics

The morphology of the solid-liquid interface and the metal phase grain diameter of Al—Si-type eutectics (Al—Si, Ag—Si, Ag—Ge, Zn—Ge) were investigated in the range of a growth rate R = 0.2 … 20 mm/h and of a temperature gradient at the solid-liquid interface G = 2 … 25 K/mm. Three types of interfacial morphologies depending on the G/R ratios were found out. The G/R ratio of the transition from a planar to a nonplanar solid-liquid interface corresponds to the critical G/R|_c ratio, which can be calculated by the criterion of the constitutional undercooling. The grain diameter of the metal phase depends on growth parameters as follows: d_K ∼ R^—rG^—g with r = 0.33 … 0.43 and g = −0.37 … 0.03.     

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.     

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.     

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.     

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.     

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.     

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 3,3-Diethyl–2,4,6–[1 H,3 H,5 H] Pyrimidine Trione

C₈H₁₂O₃N₂, M_r = 184.19, Trigonal, R3 (hexagonal axes) a = b = 26.800(1) Å, c = 6.828(3) Å, α = β = 90°, γ = 120°, V = 4247.11 ų, Z = 18, D_m = 1.297 Mg m⁻³, D_c = 1.296 Mg m⁻³, mu = 0.79 mm⁻¹, F(000) = 1764, T = 293 K, final R = 0.080 for 1205 observed reflections. There are two crystallographically independent molecules in the unit cell of the title compound.     

The Crystal and Molecular Structure of 1,18-dibromooctadecane

The crystal and molecular structures of 1,18-dibromooctadecane are determined precisely by X-ray diffraction method. The results obtained are as follows: empirical formula, C₁₈H₃₆Br₂, formula weight Mr = 412.27, crystal system, monoclinic, space group, P2₁/n, lattice parameters, a = 5.496(1), b = 5.403(1), c = 34.374(4) Å, β = 94.50(1)°, volume of unit cell, V = 1017.6(3) ų, Z value, Z = 2, calculated density, D_x = 1.346 g/cm³, wave length of X-ray, λ(CuKα) = 1.5418 Å, absorption coefficient, μ(CuKα) = 49.64 cm⁻¹, F(000) = 428.00, temperature, T = 293 ± 1 K, R factor, R = 0.052, weighted R factor, R_w = 0.078 for 1019 unique observed reflection [I > 3σ (I)]. There are no unusual bond distances or angles. The structure obtained here is quite similar to that of 1,12-dibromododecane.     

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.     

Entropy production in steady-state eutectic growth

A theoretical analysis of models for regular eutectic growth is presented. The diffusion model (practically, a relationship between interlamellar spacing, λ, and growth rate, v, proposed in JACKSON and HUNT'S theory) is localized at the paraboloid of entropy production for the process under investigation. As this paraboloid depends on the temperature and concentration gradients it is concluded that a new model which should consider both heat transfer and diffusion in the steady-state eutectic growth is to be introduced using the substantiated criterion of minimum entropy production. In this way, it is possible to obtain an equation of the f(λ, v, δT/δx) = 0 type.     

Crystal Structure Study of Co(II) Complexes with 2,2′-(1,4-Ethylenedioxyl) Dibenzoic Acid-[Co · L · (H2O)3]n · nH2O· 0.2 nH2O

The structure ofS the title complex [Co. L. (H₂O)₃]_n. nH₂O. 0.2 nH₂O has been established by single crystal X-ray diffraction. Crystals of the complex are monoclinic, space group C2/c with cell constants α = 45.29(4), b=10.631(6), c = 8.015(6) Å, β = 90.65(8)°, Z = 8, D_c = 1.489 g. cm⁻³ The structure was solved and refined to R =0.0478 (wR = 0.0577). In the chain structure, Co(II) ions are hexacoordinated by 0 atoms in an octahedral arrangement. CoO₆ octahedra share corners (bridged) through O atoms of water, with each L^2--ligand binding two adjacent Co atoms.     

Investigation of directional solidified Al–Ti alloy

Al–1 wt% Ti alloy was directionally solidified upwards under argon atmosphere under the two conditions; with different temperature gradients (G = 2.20–5.82 K/mm) at a constant growth rate (V = 8.30 μm/s) and with different growth rates (V = 8.30–498.60 μm/s) at a constant temperature gradient (G = 5.82 K/mm) in a Bridgman furnace. The dependence of characteristic microstructure parameters such as primary dendrite arm spacing (λ₁), secondary dendrite arm spacing (λ₂), dendrite tip radius (R) and mushy zone depth (d) on the velocity of crystal growth and the temperature gradient were determined by using a linear regression analysis. A detailed analysis of microstructure development with models of dendritic solidification and with previous similar experimental works on dendritic growth for binary alloys were also made.     

Crystal Structure Investigation of 2-Pheny limidazo [f]1,10-phenanthroline

The crystal structure of the title compound (PIP) has been determined by single crystal X-ray diffraction methods. C₁₉H₁₂N₄. C₂H₅OH crystallizes in the monoclinic space group P2₁/n with a = 11.4414(8), b = 12.6052(9), c = 12.4627(8) Å, β = 100.345(2)°, Z = 4, V = 1768.17 ų, D_cal = 1.286 Mg. m⁻³, μ (MoKα) = 0.80 cm^-1, F(000) = 720. The structure was solved by the direct methods and refined by full-matrix least-squares method to a final R = 0.0337 and R_w = 0.0332 for 2306 reflections with F₀ > 4σ(F₀). The phenl ring and the imidazo[f]1,10-phenanthroline moiety are coplanar in the crystal. The packing of the molecules involves hydrogen bonded association of the hydroxyl group of ethanol both with the N H of the imidazole moiety of one PIP and one nitrogen atom of the phenanthroline moiety of another PIP.     

Structure of antitumor agents 2-acetylpyridinethiosemicarbazone hemihydrate and 2-acetylpyridinethiosemicarbazone hydrochloride

The structures of two antitumor agents, 2-acetylpyridinethiosemicarbazone hemihydrate (1), C₁₈H₁₁N₄O_0.5S, colorless,M _r 203.3, monoclinic,P2₁ lc,a=16.713(3),b=9.460(2),c=12.642(2) ?, β=97.60(1)°,V=1981.2(6) ?³,Z=8,R=0.054,R _w =0.085 and 2-acetylpyridinethiosemicarbazone hydrochloride (2), C₁₈H₁₂N₄SCl, yellow,M _r =230.7, monoclinic,P2₁ ln,a=7.676(2),b=7.889(1),c=17.452(4), ?, β=100.96(2)°,V=1037.5(4) ?³ Z=4,R=0.041,R _w =0.076, have been determined. Both compounds exhibit an E configuration(S atomtrans to the N atom of the hydrazine group). Three hydrogen bonds link the two crystallographically independent molecules in a pairwise fashion in the hemihydrate. An intramolecular N−H...Cl bond lends extra conformational stability to the hydrochloride salt.     

Optical absorption of Fe3+ Ion in LiF crystals

The absorption spectrum of LiF—Fe³⁺ single crystals was investigated at liquid nitrogen temperature. Six new absorption bands, unobserved earlier in other works, were found, which were located at 11 200, 16 000, 22 700, 27300, 30 500, and 41 900 cm⁻¹. The spectrum was interpreted in the cubic cristalline field approximation with D_q = 1397 cm⁻¹, B = 657 cm⁻¹, C = 3226 cm⁻¹. Above mentioned bands were assigned to the transitions from a ground state ⁶A_1g to the levels ⁴T_1g(G), ⁴T_2g(G), ⁴A_1g(G) (⁴E_g), ⁴E_g(D), ²T_1g(F), and ⁴T_1g(F), respectively.     

Crystal and Molecular Structure of Tosyl Pyrrolidine-2-Methanol (C12H17SO3N)

C₁₂H₁₇SO₃N, M_r = 255.33, Orthorhombic, P2₁2₁2₁, a = 11.703(1) Å, b = 14.797(3) Å, c = 14.971(2) Å, V = 2592.52 ų, Z = 8, D_m = 1.309 Mgm⁻³, D_c = 1.308 Mgm⁻³, mμ = 21.57 cm⁻¹, F(000) = 1088, T = 290 K, final R = 0.080 for 2416 unique reflections. There are two crystallographically independent molecules in the unit cell of the title compound.