The Fe<Superscript>2+</Superscript>/Fe<Superscript>3+</Superscript> ratio in natural and heat-treated iron-rich eudialytes

The structures of natural iron-rich eudialyte (specimen 3458 from the Khibiny massif, the Kola Peninsula) and two heat-treated samples of this mineral calcined at 700 and 800°C were determined by X-ray diffraction. The trigonal unit-cell parameters (sp. gr. R3m) are as follows: a = 14.2645(1) Å, c = 29.9635(5) Å; a = 14.1307(1) Å, c = 30.1229(3) Å; a = 14.1921(2) Å, c = 30.2417(5) Å, respectively. It was found that Fe³⁺ ions in the calcined eudialytes, as well as impurities in the starting specimen, occupy the square-pyramidal Fe³⁺(V) sites, whereas Fe²⁺ ions are in the planar-tetragonal Fe²⁺(IV) sites.     

Investigation of zirconium phosphate Zr<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>4</Subscript> during heating

Zirconium phosphate Zr₃(PO₄)₄ has been synthesized by the sol-gel technique and investigated using X-ray powder diffraction, IR spectroscopy, and differential scanning calorimetry. It has been established that the symmetry of the unit cell, R \(\bar 3\) c, which is characteristic of the NaZr₂(PO₄)₃ (NZP) family, is lowered to P \(\bar 3\) c. The behavior of the zirconium phosphate during heating has been examined using high-temperature X-ray diffraction at temperatures ranging from 25 to 575°C. It has been revealed that the structure of the zirconium phosphate is hardly subjected to expansion due to heating in the temperature ranges 25–125°C (α _a < 1 × 10^?6 K^?1, α _c < 1 × 10^?6 K^?1, Δα < 1 × 10^?6 K^?1) and 325–575°C (α _a = ?1.4 × 10^?6 K^?1, α _c < 1 × 10^?6 K^?1, Δα < ?2.4 × 10^?6 K^?1). In the temperature range 125–325°C, the synthesized compound undergoes a second-order phase transition (upon heating), which is accompanied by the contraction of the structure along all crystallographic directions. Upon cooling in the range from 75 to 25°C, the phase transition is accompanied by the expansion of the structure.     

Microstructural study of He<Superscript>+</Superscript>-implanted and thermally annealed silicon-on-sapphire layers

The effect of He⁺ ion implantation and subsequent annealing on the silicon-on-sapphire microstructure is studied by transmission electron microscopy and X-ray diffraction analysis. It is established that He⁺ ion implantation leads to the formation of defects in the Si layer and α-Al₂O₃, while subsequent annealing causes dissociation of radiation defects in Si and formation of nanopores in α-Al₂O₃. The effect of implanted-ion dose and annealing temperature on the parameters of the porous α-Al₂O₃ layer and structural quality of the Si layer is investigated.     

Crystal Structure of a Rearranged Cage Compound, 3-Hydroxy-4-aza-8-oxoheptacyclo [9.4.1.0<Superscript>2,10</Superscript>.0<Superscript>3,14</Superscript>.0<Superscript>4,9</Superscript>.0<Superscript>9,13</Superscript>.0<Superscript>12,15</Superscript>]tetradecane

Abstract  Polycyclic hydrocarbon compounds exhibit a wide variety of biological activities, ranging from antiviral to Parkinson’s disease. Several structures such as the adamantanes have reached clinical status and are used therapeutically to treat, amongst others, neurodegenerative disorders such as Alzheimer’s. Polycyclics have also been utilised as carrier molecules to facilitate entry of drugs into the brain. The synthesis, molecular and crystal structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.0^2,10.0^3,14.0^4,9.0^9,13.0^12,15]tetradecane, are reported. NMR spectroscopy was applied for structure elucidation of the novel compound and a rearrangement mechanism is proposed for its formation. This compound crystallises in the orthorhombic system, space group Pbca (no. 61). The unit cell parameters are: a = 12.3763 (7), b = 11.6597 (6), c = 15.0539 (8) ?, V = 2172.3 (2) ?³ , and Z = 8 molecules in the unit cell. The reported structure was confirmed by X-ray analysis, which showed that the title molecules associate into centrosymmetric dimers via N–H···O hydrogen bonding. Index Abstract  The synthesis and structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.0^2,10.0^3,14.0^4,9.0^9,13.0^12,15]tetradecane, are reported in this article.      

Increase in the Fluorine-Ion Conductivity of Single Crystals of Tysonite-type CeF<Subscript>3</Subscript> Superionic Conductor by Substituting Polarized Cd<Superscript>2+</Superscript> Ions for Ce<Superscript>3+</Superscript> Ions

The fluorine-ion conductivity of single crystals with a tysonite (LaF₃) structure with heterovalent isomorphic substitutions of highly polarizable Cd²⁺ cations with a 18-electron shell for rare earth ions Ce³⁺ have been studied for the first time. Ce_0.995Cd_0.005F_2.995 single crystals have been grown from melt by the Bridgman technique in a fluorinating atmosphere. The fluorine-ion conductivity of single crystal is measured by impedance spectroscopy in the temperature range from 153 to 1073 K, where it increases by a factor of 10⁹, approaching the value σ_dc = 5 × 10^–2 S/cm at 1073 K. At T₀ = 450 ± 20 K, the dependence σ_dc(T) is split into two portions with the ion-transport activation enthalpy ΔH_σ = 0.39 ± 0.01 eV (T < T₀) and ΔH_σ = 0.23 ± 0.02 eV (T > T0). It is found that at T = 293 K the conductivity σ_dc = 3 × 10^–5 S/cm of Ce_0.995Cd_0.005F_2.995 crystal is higher by a factor of 10 than the conductivity of the tysonite matrix CeF₃ and close to the σ_dc value for Ce_0.995Sr_0.005F_2.995 crystal. This finding indicates a significant effect of the substitutions of Cd²⁺ ions for Ce³⁺ on the σdc value and the advantage of Cd²⁺ ions over Ca²⁺ and Ba²⁺ from the viewpoint of increasing σ_dc.     

Elastic and dielectric properties of A<Superscript>II</Superscript>B<Stack><Subscript>2</Subscript><Superscript>V</Superscript></Stack> (<Emphasis Type="Italic">A</Emphasis> = Cd or Zn, <Emphasis Type="Italic">B</Emphasis> = P or As) single crystals

Elastic and dielectric properties of CdP₂, ZnP₂, and ZnAs₂ single crystals are investigated at frequencies of 10², 10³, 10⁴, 10⁶, and 10⁷ Hz in the [00l], [h00], and [hk0] directions in the temperature range 78–400 K. The elastic constants, the Gruneisen parameters, and the force constants of the crystals are calculated from the measured ultrasonic velocities. The elastic constants C_ij decrease with an increase in temperature and anomalously change in narrow (ΔT = 10–20 K) temperature ranges. The permittivity sharply increases from ε ≈ 7–14 at 78–150 K to ε ≈ 10²–10³ in the temperature range 175–225 K without any signs of a structural phase transition. The behavior of the temperature-frequency dependences of the complex permittivity ε*(f, T) is typical of relaxation processes. The dielectric relaxation in A^IIB ₂ ^V is considered on the basis of the model of isolated defects. The conuctivity σ of the single crystals under study is a sum of the frequency-dependent (hopping) conductivity σ_h and the conductivity σ_s that is typical of semiconductors. The hopping conductivity increases with an increase in frequency according to the law σ _h ～f^α, where α < 1 at low temperatures and α > 1 at high temperatures.     

Internal deformations in substitutional quaternary solid solution <Emphasis Type="Italic">A</Emphasis><Superscript>3</Superscript><Emphasis Type="Italic">B</Emphasis><Superscript>5</Superscript>

A model that describes the bond-length distributions in quaternary A³B⁵ solid solutions and allows one to consider large clusters using a minimum of computational resources is suggested. The analytical expression for the radial-distribution function is obtained. The results of the modeling describe the known experimental data well. For a number of solid solutions, the deformation energy is evaluated in the approximation of the valent force field. It is shown that the main contribution to the energy comes from the bond-length dispersion.     

Growth of α-NiSO<Subscript>4</Subscript> · 6H<Subscript>2</Subscript>O crystals at high rates

The high-rate growth of nickel sulfate hexahydrate NiSO₄ · 6H₂O (α-NSH) crystals up to 120 × 120 × 65 mm³ in size is described for the first time. The data on the distribution of related impurities in the {011} and {001} growth sectors of α-NSH crystals grown at different rates are reported. The transmission spectra of both growth sectors of these crystals are obtained. The structural quality and the optical properties of rapidly and slowly grown α-NSH crystals are compared. It is established that the {011} growth sector of crystals grown at rates exceeding 5 mm/day shows the best characteristics for application in UV filters.     

Synthesis and Crystal Structure of Complex [Nd(2-FC<Subscript>6</Subscript>H<Subscript>4</Subscript>COO)<Subscript>3</Subscript>·(2-FC<Subscript>6</Subscript>H<Subscript>4</Subscript>COOH)·H<Subscript>2</Subscript>O]<Subscript>2</Subscript>

The neodymium complex with 2-fluorobenzoic acid was synthesized and characterized by X-ray diffraction. The complex crystallizes in the triclinic system with space group Pī, lattice parameters: a = 9.2747(10) Å, b = 11.7594(13) Å, c = 13.5158(14) Å, α = 110.220(2)°, β = 93.930(2)°, γ = 90.894(2)°, V = 1378.8(3) Å³, Z = 1, Dcalc = 1.733 Mg/m³. The complex is a binuclear molecule in which four 2-fluorobenzoato groups act as bidentate and tridentate bridges between the two Nd³⁺ ions. Each Nd³⁺ ion is additionally chelated by one 2-fluorobenzoato group and coordinated by one 2-fluorobenzoic acid and one water molecule.     

Absorption and Circular Dichroism Spectra of La<Subscript>3</Subscript>Ga<Subscript>5</Subscript>SiO<Subscript>14</Subscript> Crystals Doped with Pr<Superscript>3+</Superscript>, Ho<Superscript>3+</Superscript>, and Er<Superscript>3+</Superscript> Ions

The absorption and circular dichroism (CD) spectra of La₃Ga₅SiO₁₄ langasite crystals doped with Pr³⁺, Ho³⁺, and Er³⁺ ions have been studied in the wavelength range of 350–700 nm. The electronic transitions of these ions, which replace La3+ ions in the 3e position with the symmetry 2, are observed in the spectra. All transitions are active in both the absorption and CD spectra. The dipole strengths D _om, rotational strengths R _om, and anisotropy factors g have been calculated for well-resolved bands. Some features are noted for the spectra that were obtained, and their relationship with the structure disorder is considered     

Synthesis,Characterization and X-Ray Crystal Structure of the Tri Aqua (3-Hydroxy-5-Hydroxymethyl-2-Methylpyridine-4-Carboxaldehyde-3-Methylisotiosemicarbazone: k<Superscript>3</Superscript>, O<Superscript>3</Superscript>, N<Superscript>7</Superscript>, N<Superscript>10</Superscript>) Ni(II) Nitrate

Abstract  

The title complex triaqua (3-hydroxy-5-hydroxymethyl-2-methylpyridine-4-carboxaldehyde-3-methylisothiosemicarbazone-k³,O³,N⁷,N¹⁰)Ni(II) nitrate ([Ni(PLITSC)(H₂O)₃](NO₃)₂, 1) represents the second transition metal complex incorporating an isothiosemicarbazide-pyridoxal based Schiff base that has been crystallographically characterized. Complex 1 crystallizes in a P21/n space group, with lattice constants: a = 11.2254(1) ?, b = 12.9941(2) ?, c = 12.8663(2), β = 96,7713(5)°, V = 1863.64(4) ?³, Z = 4, F(000) = 1016, R ₁ = 0.0681, wR ₂ = 0.1201. The central Ni(II) cation is found in a six-coordinate octahedral geometry formed by the tridentate Schiff base ligand PLITSC and three water molecules. The identity of 1 was further confirmed by elemental analysis, IR spectra, and conductometric and magnetochemical measurements.     

Structural Conditionality of the Ionic Conductivity of MTiORO<Subscript>4</Subscript> (M = K,Rb; R = P,As) Single Crystals

The ionic conductivity σ_||c along the crystallographic axis c and the structural imperfection of the lattices of KTiOPO₄, RbTiOPO₄, and RbTiOAsO₄ single crystals with low defect concentration, grown by the high temperature solution growth technique, have been investigated by impedance spectroscopy and X-ray diffraction analysis. Isomorphic substitutions of Rb⁺ ions for conduction K⁺ cations in MTiOPO₄ crystals decreases the σ_||c value, whereas the substitution of As⁵⁺ ions for framework P⁵⁺ cations in RbTiORO₄ crystals increases the σ_||c value. The σ_||c values at 573 K are found to be 1.0 × 10^–5, 5.7 × 10^–6, 2.0 × 10^–6, and 3.3 × 10^–5 S/cm for the KTiOPO₄, RbTiOPO₄ {100}, RbTiOPO₄ {201}, and RbTiOAsO₄ crystals, respectively (the growth zone of the crystalline boule from which the samples were cut is indicated in braces).     

Influence of structural ordering on ion transport in BiO<Subscript>0.5</Subscript>F<Subscript>2.0</Subscript> bismuth oxyfluoride

The influence of structural defect ordering on ionic conductivity (σ) in the cubic (fluorite) modification of BiO_0.5F_2.0 oxyfluoride has been investigated. Upon cooling, the disordered fluorite BiO_0.5F_2.0 phase undergoes a reversible transition to an ordered form. This transition manifests itself as a jump in the temperature dependence σ(T) near 583 ± 6 K. The ordering of structural defects deteriorates the characteristics of ion transport in BiO_0.5F_2.0. At 500 K, the σ value for the ordered phase is 1 × 10⁻⁴ S/cm, whereas an extrapolation to this temperature for the disordered phase gives σ = 4 × 10⁻⁴ S/cm.     

Synthesis and Crystal Structure of 2,13-Bis(acetamido)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0<Superscript>1.18</Superscript>,0<Superscript>7.12</Superscript>]docosane Tetrachlorocobalt(II)dihydrate

Abstract The novel ionic compound [H₂bdtd][CoCl₄] · 2H₂O (1) was prepared by the reaction between CoCl₂ and 2,13-bis(acetamido)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane (bdtd) in adjusted to pH 3.0 by 1.0 M HCl and structurally characterized. The crystals are monoclinic C2/c with a = 18.7777(9), b = 9.7356(4), c = 20.0884(9) ?, β = 109.6340(10)°, V = 3458.9(3) ?³, Z = 4. The dication H₂bdtd occupies a special position about an inversion center. The cobalt(II) atom in the anion is in a distorted tetrahedral environment with four chloride ligands. The crystal structure is stabilized by a variety of hydrogen-bonding contacts involving the dication, chloride anions and solvent water molecules. Cyclic voltammetry of [CoCl₄]²⁻ anion in 1 undergoes irreversible one-electron reduction to the Co^II/Co^I. Graphical abstract The crystal structure of the ionic compound [H₂bdtd][CoCl₄] · 2H₂O (1) consists of [H₂bdtd]²⁺ cation, [CoCl₄]²⁻ anion and water molecules joined together by ionic interaction and hydrogen bonds. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Structure of amorphous oxide Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: Results of a molecular-dynamics experiment

The structure of amorphous aluminum oxide was simulated by the molecular-dynamics method. A random distribution of Al³⁺ and O^2? ions over the volumes of cubes with sides of 21 and 24 Å was used as a starting configuration. The character of the distribution of cations in the anion subsystem was analyzed. It was shown that formation of voids in model clusters is possible when the average electron density is underestimated     

TEM studies of medium-doses Kr+-implanted silicon

〈100〉 silicon wafers implanted with 300 ke V Kr⁺ ions to the following 5 × 10¹³, 1 × 10¹⁴ and 5 × 10¹⁴ cm⁻² doses were investigated by means of conventional and high voltage transmission electron microscopes. Planar-view technique was applied to characterize primary damage and to determine the geometry and the nature of secondary defects left after the furnace annealing. It is concluded that implantation to the lowest and highest doses, respectively, leads to incomplete and complete amorphicity of entire bombarded region, whereas the intermediate dose forms a burried amorphous layer. Small interstitial Frank dislocation loops on {111} planes are the predominant secondary defects for the range of doses. Occurrence of additional rod-like defects is related to the regions of discontinuous initial amorphicity.     

Structure and features of the surface morphology of <Emphasis Type="Italic">A</Emphasis><Superscript>4</Superscript><Emphasis Type="Italic">B</Emphasis><Superscript>6</Superscript> chalcogenide epitaxial films

The structure and features of the surface morphology of Pb_{1 − x} Mn _x Se (x = 0.03) epitaxial films grown on freshly cleaved BaF₂(111) faces and PbSe_{1 − x} S _x (100) (x = 0.12) single-crystal wafers were investigated by molecular beam condensation and the hot-wall method. It is shown that the epitaxial films, in accordance with the data in the literature for other chalcogenides, grow in the (111) and (100) planes, repeating the substrate orientation. Black aggregates are observed on the film surface of the films grown. The results obtained are compared with the data in the literature and generalized for other chalcogenides: A ⁴ B ⁶:Pb (S, Se, Te); Pb_{1 − x} Sn _x (S, Se, Te); and Pb_{1 − x} Mn (Se, Te). It is established that the formation of black aggregates, which are second-phase inclusions on the surface of epitaxial films obtained by vacuum thermal deposition, is characteristic of narrow-gap A ⁴ B ⁶ chalcogenides.     

Stereoselective Synthesis and X-Ray Structure Determination of Labeled [1, 2, 3-<Superscript>13</Superscript>C<Subscript>3</Subscript>]-1-(Phenylsulfinyl)-3-Benzyloxyacetone

[1,2,3-¹³C₃]-1-(Phenylsulfinyl)-3-benzyloxyacetone, C₁₆H₁₆O₃S, (3) has been synthesized and its crystal structure has been determined by a single-crystal X-ray diffraction analysis. The X-ray diffraction study revealed that compound 3 crystallizes in the monoclinic crystal system in the acentric space group Pc, with cell constants at T = 100 K: a = 16.073(5), b = 5.5079(16), c = 7.949(2) Å, β = 100.221(4)^°, V = 692.6(3) ų, Z = 2, d _calc = 1.383 g/cm³. Compound 3 contains the chiral tetravalent three-coordinated sulfur atom, which has a distorted tetrahedral configuration with a lone electron pair occupying one of the tetrahedron vertices. In the crystal, the molecules are packed in stacks along the b axis; the stacks consist of the molecules of the same chirality. Furthermore, the stacks of the molecules of the opposite chirality alternate along the c axis. The molecules in neighboring stacks are arranged by head-to-tail orientations. There are no short intermolecular contacts in the crystal of 3.     

Ionic conductivity of ScF<Subscript>3</Subscript> single crystals (ReO<Subscript>3</Subscript> type)

Electrical conductivity σ of ScF₃ single crystals (sp. gr. \(Pm\overline 3 m\), ReO₃ structure type) has been studied by impedance spectroscopy and compared with the electrical conductivity of rare earth HoF₃ (β-YF₃ type) and LaF₃ (tysonite type) trifluorides. ScF₃ crystals obtained by Bridgman directional solidification have ionic conductivity σ = 4 × 10^–8 S/cm at 673 K. It is smaller than the σ values for LaF₃ (sp. gr. \(P\overline 3 c1\)) and HoF₃ (sp. gr. Pnma) single crystals by a factor of 10⁴–10⁵. The low conductivity of ScF₃ crystals is due to the weak coordinating ability (coordination number CN = 6) and low electronic polarizability (α_cat = 1.1 ų) of Sc³⁺ ions. Mobile V_F⁺ vacancies and less mobile interstitial V_i^- ions (defects are formed according to the Frenkel mechanism) are involved in the ion transport. HoF₃ and LaF₃ single crystals have a high coordinating ability (CN = 9 for Ho³⁺ and CN = 11 for La³⁺) and a high electronic polarizability of cations (α_cat = 1.6–1.9 ų for Ho³⁺ and α_cat = 2.2 ų for La³⁺). Only mobile V_F⁺ vacancies (defects are formed according to the Schottky mechanism) are involved in ion transport.     

Crystallographic analysis of the structure of livingstonite HgSb<Subscript>4</Subscript>S<Subscript>8</Subscript> from refined data

An X-ray diffraction study of mineral livingstonite (HgSb₄S₈) from Khaydarkan (Kyrgyzstan) has been performed on a Bruker Nonius X8Apex diffractometer with a 4K CCD detector (R = 0.031). The unit-cell parameters were found to be a = 30.1543(10) Å, b = 3.9953(2) Å, c = 21.4262(13) Å, β = 104.265(1)°, V = 2501.7(2) ų, Z = 8, d _calcd = 5.013 g/cm³, and sp. gr. A2/a. It was confirmed that livingstonite belongs to rod-layers structures. In one type of layer, two double Sb₂S₄ chains are bound by disulfide groups [S₂]^2? (S-S 2.078(2) Å); in the other type, these chains are bound via Hg²⁺ cations. A crystallographic analysis confirmed the existence of independent pseudotranslational ordering in the cation and anion matrices, which is characteristic of the lozenge-like structures of sulfides and sulfosalts.