Structural analysis of bis{(N,N′–dimethylformamide) (μ‐formato)[μ‐bis(salicylidene)–1,3‐propanediaminato] nickel(II)} copper(II) and zinc(II) monohydrate hetero‐trinuclear complexes

The two linear hetero‐trinuclear metallic complexes with Cu²⁺, Ni²⁺ and Zn²⁺ ions, [CuNi₂ {(CHO₂)(SALPD)[(CH₃)₂NCHO]}₂],(I) and [ZnNi₂{(CHO₂)(SALPD)[(CH₃)₂NCHO]}₂],(II), form crystals which belong to the monoclinic system, space group P2₁/c, with unit cell dimensions a=10.537(4), b=16.612(5), c=13.837(3) Å, β=111.09(5)°, V=2259.8(12) ų in (I) and a=10.525(4), b=16.658(5), c=13.826(3) Å, β=111.11(5) °, V=2261.4(8) ų in (II), respectively. The coordinations around the M (Ni²⁺, Cu²⁺, Zn²⁺) ions in the title complexes are distorted octahedrals. The stereochemistries of the bridge ligands, linking to the metal ions each other, are changed between Ni…M (Cu²⁺, Zn²⁺) distances. The Ni…M (Cu²⁺, Zn²⁺) distances are 3.0469(13) and 3.0645(14), respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A stability diagram for crystal growth from the vapor – a review

Stability of the solid‐vapor interface is investigated. Surface roughening and evolution of flat faces at the growth interface is considered in terms of relation between gradient of temperature in the crystal and gradient of concentration in the vapor. Stability diagram is proposed, based on experimental data. The diagram summarizes the various forms and structures, which can be obtained using a typical system for growth from the vapor. The critical lines for constitutional supersaturation and appearance of low and high index faces were plotted. This attempt to the problem of stability of the growth interface differs from the former investigations mainly in looking for dependence between temperature field and concentration field rather than between more absolute parameters like temperature and supersaturation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,Crystal and Molecular Structure of 2‐Pyridylethanolbis(saccharinato)mercury(II)

2‐Pyridylethanolbis(saccharinato)mercury(II), [Hg(sac)2(pyet)], where sac and pyet are the saccharinate anion and the 2‐pyridylethanol molecule, respectively, crystallizes in the triclinic space group P (No. 2) with a = 10.4518(6), b = 11.3796(6) (5), c = 19.9945(12) Å, a = 102.758(3)° b = 98.146(3)°, g = 104.751(3)°, Z = 4, V = 2193.0(2) ų. The unit cell contains two crystallographically independent [Hg(sac)2(pyet)] units in which the mercury(II) ion is tetrahedrally coordinated by two nitrogen atoms of two sac ligands, and one nitrogen and one oxygen atoms of one neutral pyet ligands. The pyet acts as a bidentate N‐ and O‐donor ligand forming a six‐membered chelate ring, while sac behaves as a monodentate N‐donor ligand. The average bite angle of the pyet ligand is 75.8(5)°. The Hg‐N_sac bond distances are in the range 2.0874(18) and 2.1931(18) Å, whereas the Hg‐N_pyet and Hg‐O_pyet bond distances are 2.2452(19)‐2.3202(19) and 2.6036(17)‐2.5902(16) Å, respectively. The crystal exhibits two strong hydrogen bonds between the hydroxyl O atom of pyet and sulfonyl O atoms of sac and the C‐H…O type weak hydrogen bonds between H atoms of the aromatic rings of the pyet and the sulfonyl O atoms of the sac ligands. Furthermore, packing of the molecules in the solid‐state results in aromatic π‐π interactions associated with the aromatic rings of sac‐sac and py‐py.     

Crystal Structure of the Amine‐Carbonato‐Cobalt(III) Complex [Co(CO3)(L1)]ClO4 with Aminoalkyl Pendant‐Arm [12]eneN4, L1 = 9‐(3‐aminopropyl)‐1,5,9‐Triazacyclododecene

The crystal and molecular structure of the title complex [Co(CO3)(L1)]ClO4 was determined from X‐ray diffraction data using direct methods. The crystals are monoclinic, a = 13.588(4) Å, b = 9.049(3) Å, c = 15.569(6) Å, β = 114.75(2)°, Z = 4, V = 1738.5(10) ų, space group P21/n. The structure consists of isolated [Co(CO3)(C12H26N4)]+ complex cations, with distorted octahedral geometry and ClO4‐ counter anions. The results are discussed in relation to similar macrocycle and carbonato analogues.     

The Setting Behaviour of α‐ and β‐CaSO4 · 0,5 H2O as a Function of Crystal Structure and Morphology

Calcium sulphate subhydrates (CaSO₄ · x H₂O, 0 < x ≤ 0.8) have a honeycomb‐shaped channel structure. The symmetry is either trigonal or a slight deviation thereof. Due to insufficient diffraction data and the high pseudosymmetry of the structure, it is not possible at this point to determine with certainty the specific arrangement of the water molecules in the channels. When the Fourier transformation method is used to calculate the growth form of the hemihydrate (x = 0.5), the calculated crystal form corresponds to the observed form only when the trigonal structural symmetry is largely retained. During dehydration of gypsum or, conversely, during the setting process of hemihydrate, heteroepitaxial growths of hemihydrate are observed on gypsum, or gypsum is grown heteroepitaxially on hemihydrate. The (100) faces of the hemihydrate and (010) of gypsum for the most part run parallel. Using diffraction and spectroscopic methods, it can be shown that a structural difference exists between α‐ and β‐hemihydrates, and that this difference probably accounts for the different setting behaviours. It is in this context that the presence of oxonium ions, particularly in β‐hemihydrate, found in NMR experiments is of interest. Textural studies indicated that the arrangement of gypsum crystals found in hardened gypsum is determined by the hemihydrate.     

Structure of exo,exo-2,3-endo,endo-5,6-tetrabromobicycloheptane

The X-ray crystal structure analysis of the title compound, exo,exo-2,3-endo,endo-5,6-tetrabromobicycloheptane, C₇H₈Br₄, which is a product of high temperature bromination of norbornadiene, shows that the skeleton of the molecule is not changed after two bromine molecules are added via successive bromination reactions. The addition of Br₂ to both double bonds occurs (contrary to our expectation) in a syn fashion. It crystallizes in the orthorhombic space group Pbca with a = 15.688(2), b = 13.345(2), c = 9.461(1) Å, V = 1980.7(3) ų, Z = 8 and Dx = 2.762 gcm^–3.     

Growth and characterization of a novel organic NLO crystal: 4 – ethoxy benzaldehyde – n – methyl 4 – stilbazolium tosylate

The organic material 4‐Ethoxybenzaldehyde‐N‐methyl 4‐Stilbazolium Tosylate (EBST) is a new NLO material and new derivative in Stilbazolium Tosylate family. In this work we synthesized the EBST, the derivative of DAST. By slow evaporation method, we have grown the EBST crystal. Powder XRD confirms the crystalline property, the lattice parameters are calculated from single crystal XRD data and the molecular structure also revealed. The crystal system is found as monoclinic. The crystalline perfection is assessed by the high‐resolution X‐ray diffractometry. A single and reasonably sharp peak observed in the diffraction curve indicates that the quality of the crystal is quite good without having any internal structural grain boundaries. The FTIR and proton NMR study confirm the presence of functional groups. From the UV – Vis Far IR absorption spectra the good transparency is revealed. The Kurtz Perry SHG test confirms the NLO property of the EBST crystal grown and it is 11 times greater than urea. The melting point of the grown crystal is found to be 237°C from the DSC curve. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the origin of supersaturation barriers during the growth of single crystals from aqueous solutions containing impurities – a review

A generalised treatment of the appearance of supersaturation barriers σ_d, σ* and σ** during the growth of single crystals is outlined from the standpoint of well‐defined critical values of relative step velocities on a face. The final theoretical expressions are based on the premise that: (1) there are critical values of the relative step velocities associated with different average distances between adsorbed impurity particles during instantaneous, time‐dependent and time‐independent adsorption of the impurity on the growing surface, (2) the growth rate of a face is proporptional to velocity of steps on the growing face, and (3) Freundlich and Langmuir adsorption isotherms apply for different impurities. The theoretical expressions are then used to critically analyse the experimental data on supersaturation barriers observed during the growth of ammonium oxalate monohydrate and potassium dihydrogen phosphate single crystals from aqueous solutions containing different impurities. It was found that: (1) Langmuir adsorption isotherm is more practical for the analysis of the experimental data of the dependence of supersaturation barriers σ_d, σ* and σ** on the concentration c_i of an impurity, and (2) the ratios σ_d/σ* and σ*/σ** of successive supersaturation barriers for an impurity either increases or remains constant with an increase in impurity concentration c_i, and may be explained in terms of the mechanism of adsorption of impurity particles. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigation of II –VI alloy lattice dynamics by IR spectroscopic ellipsometry

Optical properties related to lattice vibrations of bulk Zn_1‐xBe_xSe, Zn_1‐x‐yBe_xMn_ySe and Cd_1‐xBe_xSe alloys are reported. Optical phonons of the mixed crystals grown by the Bridgman method have been investigated by infrared spectroscopic ellipsometry in the wave‐number range 300‐8000 cm^‐1. The complex dielectric functions can be reproduced using a model with two or three classical damped oscillators corresponding to the BeSe‐like transverse‐optical phonon‐modes and a Drude contribution from the free carriers. The frequencies of longitudinal‐optical phonons have been found from the imaginary parts of the dielectric loss functions. The influence of the alloy composition on the zone‐centre optical phonon frequencies is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Radiation induced modification of impurity‐related point defects in crystalline quartz – a review

This article presents a short review of impurity‐related point defects in crystalline quartz and their radiation induced modifications.In particular, a discussion has been presented on some of the prominent aluminum related alkali and proton compensated centers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical investigation of crystal growth process of bulk Si and nitrides – a review

Heat and mass transfer during crystal growth of bulk Si and nitrides by using numerical analysis was studied. A three‐dimensional analysis was carried out to investigate temperature distribution and solid‐liquid interface shape of silicon for large‐scale integrated circuits and photovoltaic silicon. The analysis enables prediction of the solid‐liquid interface shape of silicon crystals. The result shows that the interface shape became bevel like structure in the case without crystal rotation. We also carried out analysis of nitrogen transfer in gallium melt during crystal growth of gallium nitride using liquid‐phase epitaxy. The result shows that the growth rate at the center was smaller than that at the center. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X-ray Structure Analysis of 4–[(3,3–Dimethyloxiranyl)–methoxy]-7H-furo[3,2-g][1]benzopyran-7-one

The title compound, C₁₆H₁₄O₅, a furanocoumarin crystallizes in the triclinic space group P1 . The unit cell parameters are a = 7.852(2), b = 8.485(1), c = 11.095(1) Å; α = 105.90(1), β = 103.18(2), γ = 95.07(1)°. The structure has been solved by direct methods. Final R = 0.048 for 1943 observed reflections. The furanocoumarin system is almost planar. The epoxide ring makes a dihedral angle with the fused ring system of 98.21(11)°. Molecules are held together by C—H… O hydrogen bonds.     

Synthesis and X‐ray structure of two conformational isomers of [Zn(medpt)(SCN)2], medpt = bis (3 – aminopropyl)methylamine

Two conformational isomers of [Zn (medpt)(NCS)₂], medpt=bis(3‐aminopropyl) methylamine, (1) and (2) have been synthesised and the crystal structures are determined using single crystal X‐ray diffraction. The structures of the complexes have been solved by Patterson method and refined by full‐matrix least‐ squares techniques to R1 = 0.0524 for (1) and R1 = 0.0506 for (2), respectively. The geometry around the Zn(II) centre in both isomers is distorted trigonal bipyramidal. The two pendent thiocyanate moieties in (1), with Zn–N–C angles 167.9(4)–173.9(4)º, coordinate the mental centre almost linearly while the corresponding coordinations in (2) are significantly bent [Zn–N–C angles 150.8(3)–153.1(2)°]. Intermolecular N–H…S hydrogen bonds stabilise the crystal packing in the complexes forming infinite chains parallel to the [100] direction. The combinations of molecular chains generate three/two dimensional supramolecular framework in complexes (1) and (2). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of thiourea mixed cadmium – lead chloride – a nonlinear optical crystal

Nonlinear optical (NLO) crystal of thiourea mixed cadmium–lead chloride dihydrate Cd[(PbCl₃)(NH₂CSNH₂)].2H₂O (TCCPC) have been grown in solution by slow evaporation technique at room temperature. The powder X‐ray diffraction pattern has been recorded and indexed. The UV‐Vis‐NIR transmittance and FT‐IR spectrum have been recorded in the range 200‐1090 nm and 400‐4000 cm^‐1, respectively. The lower cut‐off wavelength is 280 nm in the UV region, which is higher than that of pure Cd(PbCl₃) (CCPC) crystal. The presence of functional groups has been confirmed by FT‐IR analysis. The TCCPC crystal was characterized by SEM and EDX spectrum. The second harmonic generation (SHG) of the thiourea mixed cadmium–lead chloride (TCCPC) crystal is demonstrated by the Kurtz Perry method using Nd:YAG laser and the results confirm that the grown crystal is roughly three times more efficient than ADP. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth rate dispersion — a review

The growth rate dispersion (GRD) is reviewed from its start up to today. A definition is given followed by a summary of the facts and the first approaches for explanations. This all are surface reaction steps. The discussion of the consequences – no size dependent growth – is carried through. At the end the models (RF-and CCG-model) will be introduced which make it possible to work with the growth rate dispersion instead of size dependent growth. The newest approach is the superpositioning of the two models, this is perhaps the most promising way.     

Synthesis,crystal structure and vibrational characterization of bis‐μ‐peroxo‐hexacarbonatodicerate(IV) complexes of rubidium and cesium

The new compounds Rb₈[Ce(O₂)(CO₃)₃]₂ · 12 H₂O (1) and Cs₈[Ce(O₂)(CO₃)₃]₂ · 10 H₂O (2) were obtained from the reaction of hydrogen peroxide and Ce(III) in saturated alkali carbonate solutions. The crystal structures and the unit cell parameters of (1) triclinic, P‐1 with a = 8.973(2) Å, b = 10.815(2) Å, c = 11.130(3) Å, α = 66.992(2)°, β = 68.337(2)°, γ = 74.639(2)°, V_EZ = 914.7(4) ų, Z = 2, and (2) orthorhombic, Pbca, a = 19.3840(16) Å, b = 18.528(2) Å, c = 10.487(3) Å, V_EZ = 3766.4(13) ų, Z = 8, were determined. Both compounds contain the bis‐µ‐peroxo‐hexacarbonatodicerate(IV)‐ion, [(CO₃)₃Ce(O₂)₂Ce(CO₃)₃]^8‐. IR and Raman spectra were measured and discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and Structure of Trans‐bis(ethanolamine)bis(saccharinato)mercury(II)

Trans‐bis(ethanolamine)bis(saccharinato)mercury(II), [Hg(ea)₂(sac)₂], where ea and sac denote the ethanolamine molecule and the saccharinate anion, respectively, crystallizes in the triclinic space group P (No. 2) with a = 9.4651 (5), b = 10.4365 (5), c = 11.9314 (6) Å, α = 84.402 (1)° β = 78.313 (1)°, γ = 75.307 (1)°, Z = 2, V = 1115.11 (10) ų. The structure consists of isolated [Hg(ea)₂(sac)₂] units in which the Hg(II) ion is octahedrally coordinated by two nitrogen and two oxygen atoms of two neutral ea ligands, and two nitrogen atoms of two sac ligands. The ea acts as a bidentate N‐ and O‐donor ligand and occupies the trans positions of the equatorial plane of the coordination octahedron forming a fivemembered chelate ring, while sac behaves as a monodentate N‐donor ligand occupying the axial positions. The average Hg‐N_sac and Hg‐N_ea bond distances are 2.739 (3) and 2.114 (7) Å, respectively. The crystal exhibits extensive hydrogen bonds between the hydroxyl and amine hydrogen atoms of the ea ligands and the sulfonyl, carbonyl and amine groups of the sac ligands.     

Selective epitaxy and lateral overgrowth of 3C-SiC on Si – A review

This review article attempts to present a comprehensive picture of the progress in selective epitaxial growth (SEG) of cubic silicon carbide (3C-SiC) to make it a cheap and practical material for high temperature and high power, high frequency and MEMS (Micro Electromechanical Systems) applications. Selective epitaxial growth followed by epitaxial lateral overgrowth (ELO) is a suitable approach to minimize the interfacial defects and other planar defects in case of thin film growth. Different techniques of SEG and its application to Si, GaAs and III–V nitrides are reviewed briefly in the first section of this article. Various SEG techniques like epitaxial lateral overgrowth, pyramidal growth and pendeo epitaxial growth, etc. have been discussed extensively for growing 3C-SiC on Si, together with the characterization of the grown films. The influence of various experimental parameters such as temperature of growth, choice of mask material, influence of an etchant, pattern shape and size, etc. is also discussed. On the basis of these data, it is believed that SEG and related techniques are a promising approach for heteroepitaxial growth of 3C-SiC films useful for devices and MEMS applications.     

Crystal structure of a daturalactone – A withanolide

The crystal structure of a daturalactone derivative has been determined by X-ray structural analysis. The compound crystallizes in orthorhomic space group P2₁2₁2₁ with cell parameters a - 15.141(1) Å, b - 18.425(1) Å, c - 19.251(2) Å. The structure was solved by direct methods and refined to R - 0.082. The asymmetric unit contains two non-equivalent molecules. Extensive hydrogen bonding is present. The conformations of the rings are A: a distorted half-chair, B: a perfect half-chair, C: a chair, D: an envelope-half chair and E: a twist boat. Ring junctions A/B, B/C, C/D are all trans fused. Methyl carbons C(18), C(19), C(27) and the lactone moiety is β-oriented whereas the methyl carbons C(21) and C(28) are α-oriented.     

Crystal Structure of (Cr,Cu)(Sr,La)2(La,A)Cu2O8‐δ (1212‐type) and (Cr,Cu)Sr2(Y,Ce)2Cu2O10‐δ (1222‐type) Phases

Conditions of the synthesis, crystal structures, mechanical properties, electrical resistivities and magnetizations of cuprates with the general formula (Cr,Cu)(Sr,La)₂(La,A)Cu₂O_8‐δ where A=Ca or Sr of 1212‐type and (Cr,Cu)Sr₂(Y,Ce)₂Cu₂O_10‐δ of 1222‐type were investigated. The compositions of the cuprates and an amount of the impurity phases in the samples were determined. Rietveld refinement of the structure was carried out. It was found that the formal charges of Cu (FC_Cu) calculated from the electroneutrality of refined phase compositions do not achieve value optimal for the appearence of superconducting phases.