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The results of the studies performed at the Shubnikov Institute of Crystallography and devoted to the development of UV optical filters based on complex nickel and cobalt compounds are reviewed. The structural dependence of the optical properties of these crystals and their thermal stability is discussed. The fundamental features of mixed crystals grown from solution and developed approaches to the design of optical filters based on structurally perfect mixed K2(Co,Ni)(SO4)2⋅6H2O crystals are described. The possibility of designing UV-А optical filters by partial substitution of the ligand environment of transition metal ions is demonstrated. [ABSTRACT FROM AUTHOR]

The growth system has been upgraded, technological growth parameters have been optimized, and a high-quality crystal has been grown from the LiNb0.95Ta0.05O3 charge. Spectral dependences of the transmittance of a sample cut from this crystal have been measured before and after the transition to the single-domain state in the range of 300–700 nm with allowance for anisotropy and dichroism. Spectral dependences of the absorption coefficient α(λ) and degree of dichroism Δ(λ) have been obtained. The dependences α(λ) contain an absorption band at λ ~ 480 nm, regardless of the light propagation direction. When light propagates perpendicular to the optical axis, absorption bands at λ ~ 560, 608, 620, and 656 nm can additionally be observed. The transition to the single-domain state leads to sample bleaching. The dependences Δ(λ) for the X and Y cuts are characterized by identical extrema, whose positions correspond to the absorption bands in the dependences α(λ); additional extrema manifest themselves at λ ~ 400 and 445 nm. When light propagates along the optical axis, the dependences Δ(λ) are nonzero; they are characterized by much smaller values (in comparison with the directions perpendicular to the optical axis) and have extrema at λ ~ 440, 560, 600, 620, and 640 nm. [ABSTRACT FROM AUTHOR]

The growth system has been upgraded, technological growth parameters have been optimized, and a high-quality crystal has been grown from the LiNb0.95Ta0.05O3 charge. Spectral dependences of the transmittance of a sample cut from this crystal have been measured before and after the transition to the single-domain state in the range of 300–700 nm with allowance for anisotropy and dichroism. Spectral dependences of the absorption coefficient α(λ) and degree of dichroism Δ(λ) have been obtained. The dependences α(λ) contain an absorption band at λ ~ 480 nm, regardless of the light propagation direction. When light propagates perpendicular to the optical axis, absorption bands at λ ~ 560, 608, 620, and 656 nm can additionally be observed. The transition to the single-domain state leads to sample bleaching. The dependences Δ(λ) for the X and Y cuts are characterized by identical extrema, whose positions correspond to the absorption bands in the dependences α(λ); additional extrema manifest themselves at λ ~ 400 and 445 nm. When light propagates along the optical axis, the dependences Δ(λ) are nonzero; they are characterized by much smaller values (in comparison with the directions perpendicular to the optical axis) and have extrema at λ ~ 440, 560, 600, 620, and 640 nm. [ABSTRACT FROM AUTHOR]

The optical properties of Sr3NbFe3Si2O14, Ba3NbFe3Si2O14, and Ba3TaFe3Si2O14 single crystals (promising multiferroics belonging to the langasite family (sp. gr. P321, Z = 1)) have been investigated. The crystals have been grown by floating zone melting. The measured and calculated refractive indices of these crystals are compared. The optical activity parameters are calculated based on the structural data. The atomic structures are compared proceeding from the precise X-ray diffraction analysis data. A correlation is established between the structural features and optical properties of the crystals. [ABSTRACT FROM AUTHOR]

A comparative study of the optical and structural homogeneity of a LiNbO3 crystal with a congruent composition and LiNbO3 : ZnО ([ZnО] ≈ 5.4–6.4 mol % in melt) crystals grown from charges of different origin has been performed. It is shown that the LiNbO3 : ZnО crystals obtained by direct solid-phase doping have a higher general structural and optical homogeneity, provided that the crystal composition is sufficiently homogeneous along the growth axis. Homogeneously doped LiNbO3 : ZnО crystals, characterized by a high general structural homogeneity on the scale level of 10–500 µm, have poorer optical and structural homogeneity on the micron and submicron levels as compared with directly doped LiNbO3 : ZnО crystals. [ABSTRACT FROM AUTHOR]

Aqueous solutions of guanylurea hydrogen phosphite (GUHP) have been synthesized. The temperature dependence of equilibrium GUHP concentration in water was obtained. The change in the density of aqueous GUHP solutions with a change in their concentration was investigated. The influence of the solution pH on the GUHP solubility in water in the temperature range of +25–45°C was analyzed. The crystallization range of monoclinic GUHP crystals, belonging to the sp. gr. Cc, was determined. GUHP crystals were grown using different methods, based on cooling or maintaining a constant temperature, with mixing aqueous solutions or without mixing. The properties of the grown crystals in the optical and THz ranges were investigated. [ABSTRACT FROM AUTHOR]

Abstract: A series of three-component isostructural fluorite crystals (Sr1-xBax)0.7La0.3F2.3 (sp. gr. , 0 ≤ x ≤ 1), the compositions of which belong to the Sr0.7La0.3F2.3-Ba0.7La0.3F2.3 polythermal section in the SrF2-BaF2-LaF3 system, has been grown for the first time by vertical directional crystallization. Optical, mechanical, and electrical properties of three-component (Sr1-xBax)0.7La0.3F2.3 and two-component M0.7La0.3F2.3 (M = Sr or Ba) crystals have been investigated and subjected to comparative analysis. It is shown that all three-component crystals (Sr1-xBax)0.7La0.3F2.3 are promising optical design materials. [ABSTRACT FROM AUTHOR]

Abstract: Potassium cobalt sulfate hexahydrate (K2Co(SO4)2 · 6H2O, KCSH) crystals have been grown at a supersaturation σ in the range of 2-8.1%. The optimal conditions for KCSH crystal growth are refined by reducing the solution temperature. The real structure of crystals and their optical properties are investigated. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the imperfection of optical elements of a spectrophotometric system on the polarization transmission spectra of a uniaxial optically active absorbing plate has been analyzed by the example of a La3Ta0.25Ga5.25Si0.5O14 crystal, belonging to the langasite family. A comparison of the calculated and experimental transmission spectra for two samples with different thicknesses and optical-axis orientations shows that the optical-activity parameters of a crystal and the angle of deviation of the optical axis from the normal (when this angle is small) can be estimated. [ABSTRACT FROM AUTHOR]

The polarization azimuths and ellipticities of the reflected and transmitted light have been calculated as functions of the angle of incidence for transparent crystals of classes $$\overline 4 $$ 2 m and $$\overline 4 $$ . Analytical expressions for these parameters are obtained. It is shown that in the general case the polarization azimuths and ellipticities for a plate cut parallel to the optical axis differ for positive and negative angles of incidence of light. [ABSTRACT FROM AUTHOR]

The influence of the antisymmetric part of the gyration pseudotensor on the characteristics of reflected and transmitted light has been considered for crystals of classes 3, 4, and 6. The results are compared with the corresponding data for crystals of classes 32, 422, and 622 with a symmetric gyration pseudotensor. Specific features of the optical activity in crystals of classes 3 m, 4 mm, and 6 mm with an antisymmetric gyration pseudotensor have been studied. Crystals of classes $$\bar 42m$$ and $$\bar 4$$ with the symmetric gyration pseudotensor of an unusual form have been considered. The polarization azimuth and ellipticity of the reflected and transmitted light are calculated for these crystals at different angles of incidence. [ABSTRACT FROM AUTHOR]

The influence of the antisymmetric part of gyration pseudotensor on the characteristics of transmitted light have been investigated for biaxial crystals. Analytical expressions for the optical rotation in the direction of optical axis are obtained with allowance for both the symmetric and antisymmetric parts of gyration pseudotensor. The polarization azimuth and transmitted light ellipticity have been calculated at different angles of incidence. [ABSTRACT FROM AUTHOR]

The single-crystal structure of cooperite, a natural platinum sulfide PtS, is studied by X-ray diffraction supported by high-resolution scanning transmission electron microscopy and X-ray spectrum microanalysis. It is found that, in addition to the main reflections corresponding to the known tetragonal cell ( a = 3.47 and c = 6.11 Å; space group P4/ mmc), many weak reflections with intensities I ≤ 60 σ( I) are clearly observed. These reflections fit the tetragonal cell (space group I4/ mmm) with doubled parameters. In structures with small ( P4/ mmc) and large ( I4/ mmm) cells, the S atoms occupy statistically two special positions. It is shown that the chemical composition of the cooperite crystals deviates from the stoichiometric composition: sulfur-deficient specimens predominate. [ABSTRACT FROM AUTHOR]

An accurate X-ray diffraction study of CaTaGaSiO single crystal has been performed using two datasets obtained on a diffractometer equipped with a CCD area detector ( a = 8.1056(2) Å, c = 4.9800(1) Å, sp. gr. P321, Z = 1, R/ wR = 0.486/0.488%). A model structure is determined which is characterized by a high degree of reproducibility of structural parameters. Each site in CaTaGaSiO is occupied by atoms of only one type. Nevertheless, its structural feature is asymmetric disordering of sites of Ca, Ta, Ga, and two out of three oxygen atoms occupying special and general sites. A transition of some part of Ca atoms (~3%) from 3 e sites on the twofold symmetry axis to general 6 g sites is revealed. [ABSTRACT FROM AUTHOR]

The hypotheses about the nature of color centers in langasite family crystals that are discussed in the literature are analyzed. Optical transmission spectra in the wavelength range of 200-800 nm are recorded for langasite and langatate crystals grown in atmospheres of argon and argon mixed with oxygen in different concentrations, both in the initial state and after isothermal annealings at 1000°C in nitrogen, in air, or in vacuum. Dichroism is observed in langasite and langatate crystals, and spectral dependences of the degrees of dichroism are plotted. [ABSTRACT FROM AUTHOR]

The main factors and specificity of growth conditions for sapphire and Ti:sapphire crystals, which affect the morphological stability of the crystal-melt interface, have been investigated with allowance for the concentration and radiative melt supercooling. It is shown that the critical sapphire growth rate is determined to a great extent by the optical transparency of the melt and the mixing conditions near the crystallization front. [ABSTRACT FROM AUTHOR]

Thermophysical characteristics of SrMoO crystals (grown by the Czochralski method from intrinsic melts), nominally pure and doped with rare earth ions, have been investigated. The temperature and concentration dependences of the thermal conductivity are obtained for SrMoO samples containing Nd (0.28, 0.56, 0.84, and 1.33 at %), Pr (0.01 and 0.41 at %), Ho (0.01 and 0.06 at %), and Ho (0.13 at %) + Tm (0.13 at %) in a temperature range of 50-300 K. The thermal conductivities are measured in the directions parallel and/or perpendicular to the crystal optical axis. The thermal conductivity of nominally pure SrMoO at 300 K in the direction perpendicular to the c axis has been found to be 4.2 W/(m K). The introduction of impurities of rare earth metals reduces the thermal conductivity of SrMoO crystals. The anisotropy of the thermal conductivity is weak. The measured molar specific heat C( T) of a nominally pure SrMoO crystal is 116.2 J/(mol K) at 300 K. The temperature dependence of the phonon mean free path l( T) in a SrMoO crystal is calculated for the temperature range of 80-300 K based on experimental data. [ABSTRACT FROM AUTHOR]

Media with unconventional wave-vector surfaces are systematized with respect to the shape of their surfaces. The characteristic optical features of these media, caused by new forms of wave vector surface (atypical of conventional optics), are indicated. [ABSTRACT FROM AUTHOR]

An X-ray diffraction study of α-HIO crystal has been performed with the following results: sp. gr. P222, Z = 4, a = 5.5360(3) Å, b = 5.8723(6) Å, c = 7.7291(5) Å, and R factors R( F)/ wR( F) = 0.86/0.69%. Disordering of iodine site is revealed, which is described in terms of anharmonic atomic displacements. Packing (likely unique) of all structure atoms over two systems of planes rotated by an angle close to the rotation of optical axes (47°) is revealed. The rotation of the plane of polarization of light based on the structural data is calculated for the first time for the α-HIO crystal. [ABSTRACT FROM AUTHOR]

It is shown that interference can be implemented in the optical scheme of an Olimpus Lext-3000 laser scanning microscope. The occurring interference patterns are differently localized in space, depending on the experimental conditions. Interference from opposite crystal (volume) faces can be observed under certain conditions, which makes it possible to visualize (with a high sensitivity) defects that are invisible in polarized light and the surface relief. Misorientations and deformations in a crystal can be estimated. Our analysis allowed us to interpret the in situ observed interference pattern from growing lisozyme protein crystals and KCo(SO) · 6HO crystals. [ABSTRACT FROM AUTHOR]

MgF single crystals have been grown from melt by the Bridgman technique in a fluorinating atmosphere. To control the presence of oxygen impurity, it was first suggested to measure the ionic conductivity in MgF crystals by impedance spectroscopy. The characteristics of ionic conductivity of ' as grown' (i.e., without thermal treatment) crystals and crystals obtained by commercial vacuum technology practically coincide: the volume conductivity σ = 1.4 × 10 S/cm at 773 K and the ion-transport activation energy E = 1.40 ± 0.05 eV. Annealing MgF crystals during electrophysical studies upon heating from 293 to 823 K in vacuum (residual pressure ∼1 Pa) for 4 h led to their partial pyrohydrolisis. The influence of this thermal treatment of MgF crystals on their optical transmission is studied in the wavelength range of 115-300 nm. [ABSTRACT FROM AUTHOR]

Various manifestations of optical activity (OA) in crystals and organic materials are considered. Examples of optically active enantiomorphic and nonenantiomorphic crystals of 18 symmetry classes are presented. The OA of enantiomorphic organic materials as components of living nature (amino acids, sugars, and proteins) is analyzed. Questions related to the origin of life on earth are considered. Examples of differences in the enantiomers of drugs are shown. The consequences of replacing conventional left-handed amino acids with additionally right-handed amino acids for living organisms are indicated. [ABSTRACT FROM AUTHOR]

The possible numbers of optical axes in absorbing triclinic crystals have been considered. Most of these crystals possess four circular optical axes; however, there may be crystals having one isotropic optical axis, two or three circular optical axes, or simultaneously one isotropic and one or two circular optical axes. It is shown that particular cases significantly differ from the general case of crystal with four circular axes. The dependence of the form of the complex permittivity tensor on the number of optical axes is presented. The ellipticities of eigenwaves and the transmitted-light ellipticity in the case of normal incidence of a wave with a right- or left-hand circular polarization are calculated for these crystals. [ABSTRACT FROM AUTHOR]

The symmetry (sp. gr. I$\bar 4$ 3 d) and lattice parameters have been determined for the first time for Cs 5(H 2SO 4) 2(H 2PO 4) 3 crystals in the temperature range from 172 to 390 K. The thermal and optical properties of crystals, as well as their conductivity, have been investigated at elevated temperatures. It is shown that a crystal heated to T = 365 K undergoes a phase transition with symmetry lowering to the tetragonal phase (with the parameters a = 4.965(1) Å and c = 5.016(1) Å), while at T ≈ 390 K a phase transition to the cubic phase is presumably observed. With a decrease in temperature, a phase transition without a change in symmetry occurs at T = 240 K. [ABSTRACT FROM AUTHOR]

An X-ray diffraction study of ZnO crystals grown by the hydrothermal method has revealed reflections that give grounds to assign them to the sp. gr. P3 rather than to P6 mc. The distribution of Zn1, Zn2, O1, and O2 over structural positions, along with vacancies and incorporated zinc atoms, explains the dissymmetrization observed in terms of the kinetic (growth) phase transition of the order-disorder type, which is caused by ordering Zn and O atoms over structural positions. The color of crystals of refined compositions (Zn□)Zn(O□) (green) and (Zn□)ZnO (bright green) is related to different oxygen contents, which is confirmed by the results of electron probe X-ray microanalysis and absorption spectroscopy. The degree of the structural quality of crystals, their resistivity, and activation energy are also related to oxygen vacancies. [ABSTRACT FROM AUTHOR]

The prospects of increasing the resolution of the DIN-2PI spectrometer at initial neutron energies of 50-500 meV are discussed. The spectrometer resolution can be significantly improved using time-of-flight neutron monochromatization supplemented with a monochromator crystal. The application of this combined monochromatization technique makes the dependence that the instrumental resolution has on the duration of the neutron pulse from the IBR-2 reactor insignificant. This update will make it possible to perform experiments with initial neutron energies to several hundreds of meV in the energy-dumping mode, which, in turn, allows one to study condensed media in a wide range of temperatures, including cryogenic. [ABSTRACT FROM AUTHOR]

Peculiarities of the manifestation of optical activity and absorption in crystals of the orthorhombic system of the 222 class are considered. The influence of each effect on the ellipticities of eigenwaves is analyzed. The dependences of the azimuth, ellipticity, and intensity of transmitted light in directions slightly and significantly deviating from the optical axes are considered in detail. Cases are indicated where the approximate relations obtained disregarding multiple reflections and nonorthogonality of eigenwaves in crystal hold true. The differences of the simulated conoscopic patterns of the biaxial absorbing optically active crystals from the patterns of inactive or nonabsorbing crystals are analyzed. [ABSTRACT FROM AUTHOR]

The kinetic, optical, and dielectric properties of YFeO garnet single crystals of different structural quality have been investigated. It is established that the ratio of the intensities of coherent and incoherent scattering characterizes the conduction electron concentration in inhomogeneous magnetic samples. A correlation between the physical properties of the samples and the character of their structural inhomogeneity is revealed. [ABSTRACT FROM AUTHOR]

BiSiO crystals have been grown for the first time by the low-thermal gradient Czochralski technique in the 〈111〉 and 〈110〉 directions. The conditions for reproducible crystal growth with a high-quality polyhedral faceted front are found. The systematic features of shaping BiSiO and BiGeO crystals, grown by the low-thermal gradient Czochralski technique, are compared. The defect formation in these crystals is studied and their optical homogeneity is analyzed by interferometry. [ABSTRACT FROM AUTHOR]

The effect that uniaxial pressures along the principal crystallophysical directions have on the dispersion and temperature dependences of the birefringence in incommensurate KZnCl crystals has been investigated in a wide temperature range. This parameter has been established to be fairly sensitive to uniaxial pressures. The spectral and temperature dependences of combined piezo-optic coefficients are analyzed. Significant anomalies of these coefficients are found at the incommensurate-commensurate phase transition. They are due to the change in the induced birefringence that results from spontaneous polarization and to the significant effect of uniaxial stress on the soliton structure of the crystal. The contributions that the electrooptic effect, the elasto-optic effect, and the order parameter make to the spontaneous changes in the piezooptic coefficients are separated. [ABSTRACT FROM AUTHOR]

The frequency dependence of the reflection coefficient of MgF crystal in the frequency range of 200-800 cm at different orientations of the optical axis has been investigated. The experimental data are compared with the calculation results. This comparison confirms that the wave vectors for the extraordinary wave have an open surface. This makes it possible to focus a divergent beam refracted at a flat boundary ori- ented perpendicularly to the optical crystal axis. The focusing effect of a plane-parallel MgF crystal plate is calculated. [ABSTRACT FROM AUTHOR]

The optical birefringence, optical indicatrix rotation, and residual intensity have been experimentally investigated in the parent and incommensurate phases of [N(CH3)4]2ZnCl4 crystals doped with Ni2+. The temperature dependences obtained are nonlinear in a wide temperature range ( T i − 360 K). It is shown that the nature of this nonlinearity is related to the presence of local spatial regions of the correlated motion of tetrahedral groups. It is established that the deformation of tetrahedral groups increases the temperature range of existence of these regions. [ABSTRACT FROM AUTHOR]

This paper reports on the results of the precision X-ray structural investigations of KTi0.96Zr0.04OPO4 single crystals at room temperature. It is established that the incorporation of zirconium atoms into the structure of KTiOPO4 (KTP) crystals does not lead to substantial changes in the framework structure and results only in an insignificant decrease in the scatter of the distances in the PO4 tetrahedra and the formation of more symmetric (TiZr)O6 octahedra as compared to the TiO6 octahedra. However, the incorporation of zirconium atoms into the KTP structure is accompanied by the redistribution of the electron density in the crystal as a whole, so that the electron density increases in the region of the positions occupied by the potassium atoms. This changes the nonlinear optical properties of the given series of crystals, which are estimated from the intensity of the second harmonic generation signals. [ABSTRACT FROM AUTHOR]

Crystals of langasite La3Ga4(GaSi)O14 grown by the Czochralski method are studied using neutron diffraction for the first time. It is established that the compositions of the upper and lower parts of an orange crystal grown from the La3Ga5.14Si0.86O14 seed in an (Ar + O2) atmosphere (the 〈 0001 〉 growth direction) can be written as(La2.85(2)□0.15)(Ga0.95(2)□0.05) Ga3(Ga1.15 Si0.85(5))(O13.72□0.28(7)) and(La2.89(1)□0.11)·(Ga0.98(1)□0.02) Ga3(Ga1.06Si0.94(4))(O13.81□0.19(9)), respectively. The La content in the upper and lower parts of this crystal is lower and higher than the Ga content, respectively, and the Ga content exceeds the Si content in the (GaSi) position. By contrast, in a colorless crystal of the composition(La 2.97(4)□0.03) Ga(1)(Ga2.94(9)□0.06)(Ga0.7(1) Si1.3)(O13.9□0.1(1)), which is grown from the La3 Ga5SiO14 seed in an argon atmosphere (the 〈 01 $$ \bar 1 $$ 1 ⌚growth direction), the Ga content in the (GaSi) position is lower than the Si content. A relation between the Ga: Si ratio and the (Ga,Si)-3O interatomic distances is found. [ABSTRACT FROM AUTHOR]

Specific features of UV lasing in low-dimensional zinc oxide materials have been investigated. Two main types of lasers, differing in the feedback formation mechanism-classical random lasers and microlasers—have been selected in active disordered zinc oxide materials. In the first case, feedback is provided by strong light backscattering, and a large number of scattering particles are involved in the cavity formation. In the second case, each crystallite operates as an individual microlaser. The main lasing spectral parameters are reported for the distinguished types of lasers. [ABSTRACT FROM AUTHOR]

The reactivity of viscous melts has been analyzed as a function of the degree of anion polymerization. Precise techniques are proposed for detecting the phase relations and kinetics of high-temperature crystallization of new materials in four-to-six-component borate and tantalate systems. For rare earth polyfunctional borates RAl3(BO3)4 ( R = Y or lanthanides), efficient frequency conversion with parameters greatly exceeding the corresponding parameters for known media has been demonstrated for the first time. The conditions for fabrication of refractory optical single crystals having high thermal conductivity and other record characteristics (in comparison with the known diode-pumped lasers) for femtosecond integrated optics have been optimized. Bases of the laboratory technology of growth of such crystals are considered. [ABSTRACT FROM AUTHOR]

Optical properties of quasicrystalline Al-Pd-Re films have been investigated in the mid and far IR regions. Films were deposited on sapphire substrates using layer-by-layer ion-plasma sputtering with subsequent vacuum annealing. Reflection spectra have been measured in a wide IR spectral range from 50 to 7500 cm−1. The complex dielectric function of the films was determined from the experimental data by dispersion analysis of the reflection spectra. The frequency dependence of the real part of the optical conductivity was calculated. [ABSTRACT FROM AUTHOR]

The solid electrolytes with fluorine-ion conductivity that were revealed during the analysis of the phase diagrams of the MF m - RF n systems within the program of search for new multicomponent fluoride crystalline materials carried out at the Shubnikov Institute of Crystallography, Russian Academy of Sciences, are described. The most widespread and promising materials are the nonstoichiometric phases with fluorite (CaF2) and tysonite (LaF3) structures, which are formed in the MF2- RF3 systems ( M = Ca, Sr, Ba, Cd, or Pb; R = Sc, Y, or La-Lu). These phases have superionic fluorine conductivity due to the anion sublattice disorder. The ionic conductivity of crystals of both structure types has been studied and the limits of its change with composition and temperature are determined. Nonstoichiometric fluorides are used as solid electrolytes in chemical sensors, fluorine sources, and batteries. The prospects of the use of fluorine-ion conductors in solid-state electrochemical devices, principles of their operation, and the problems of optimization of their composition are discussed. [ABSTRACT FROM AUTHOR]

Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1− x R xF2+ x ( R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. [ABSTRACT FROM AUTHOR]

Specific features of manifestation of optical activity in cubic, uniaxial, and biaxial crystals are described. The effect of optical activity on characteristics of transmitted light is considered as a function of the wavelength of incident light, temperature, and the orientation the optical axis. The results of the investigation of crystals of different symmetry classes are reported. [ABSTRACT FROM AUTHOR]

The state of the art of electrodynamics of new composite media—metamaterials—is reviewed. The composites in the form of a periodic lattice of identical elements, which are in essence artificial crystals with characteristic scales of the internal structure from several centimeters to several hundred nanometers are considered. The most important properties of metamaterials and the specific features of propagation of electromagnetic signals in these media are described. Particular attention is paid to the conventional methods of condensed-matter physics, which have found application in the electrodynamics of metamaterials and have provided dynamic development of this new field of science and technology. [ABSTRACT FROM AUTHOR]

Crystals of the R 1 − y Sr y F3 − y phases ( R = La, Ce, Pr, or Nd; 0 ≤ y ≤ 0.16) with tysonite (LaF3) structure are grown by the Bridgman method. A linear dependence of the crystal density on the SrF2 concentration has been revealed for each series of solid solutions. A scheme of heterovalent isomorphous substitution in the tysonite structure, R 3+ + F1− → M 2+ + V F, with compensation of the difference in the cation charges due to the formation of anion vacancies, is confirmed experimentally. The optical transmission spectra are measured in the wavelength range λ = 2.18–22.22 μm. It is shown that the 50%-transmission edge in the IR range is 10.5 μm for all crystals. The refractive index and the polarizability of crystals decrease with decreasing SrF2 content according to a linear law. The melting curves of the R 1 − y Sr y F3 − y phases studied have a maximum; therefore, these phases can be recommended for use as crystals with a high homogeneity and different optical properties in comparison with the corresponding RF3 crystals. [ABSTRACT FROM AUTHOR]

A new polar representative of the hilgardite structural family, Na0.5Pb2[B5O9](OH)1.5 · 0.5H2O (space group Pnn2), is synthesized under hydrothermal conditions. The crystal structure of the compound synthesized is similar to the structure of the previously studied polar compound Na0.5Pb2[B5O9]Cl(OH)0.5 and is intermediate between the latter compound and the centrosymmetric hydrate Pb2[B5O9](OH) · 0.5H2O. The additional peak revealed in the electron density in the vicinity of the Pb(1) atom is attributed to the stereochemically active lone electron pair of this atom. The lone electron pair is oriented toward the two most distant oxygen atoms involved in the Pb(1) coordination environment, namely, O(7) and O(2), which are located in a boron-oxygen framework layer in the ac plane, not toward the (00z) channel occupied by water molecules. The nonequivalence in the stereochemical activity of two lead atoms [Pb(1) > Pb(2)] is similar to that observed in the nonlinear optical borate Pb2[B4O5(OH)4](OH)2 · H2O related to BiB3O6. [ABSTRACT FROM AUTHOR]

Investigation of the optical properties of natural violet diamonds from the Yakutian kimberlites is performed. A red shift of the absorption edge is revealed in the absorption spectra of these crystals. This shift is indicative of the presence of a high concentration of nitrogen in the diamonds studied. Along with the strong band at 0.550 μm, weaker bands at 0.390, 0.456 and 0.496 μm are revealed. It is shown that violet diamond crystals have birefringence and dichroism of about 10−5 and 10−6, respectively. When a light beam propagates perpendicularly to colored lamellas, the dichroism is much larger and the birefringence is smaller than in the case where the beam direction is parallel to lamellas. [ABSTRACT FROM AUTHOR]

The character of nonuniform distribution of the main cations Y and Fe in the plane of samples of yttrium garnet Y3Fe5O12 and the nonstatistical incorporation of process impurities along the crystallographic directions [110], [111], and [100] are investigated. The structural inhomogeneity revealed in the samples is discussed with allowance for the difference in the growth rates of the garnet crystal faces under study, specific features of the incorporation of dominant impurities, and the relationship between this inhomogeneity and the optical and kinetic properties of the crystals. [ABSTRACT FROM AUTHOR]

High-quality single crystals of the high-temperature phase of barium metaborate (α-BaB2O4) up to 100–120 g in weight are grown from a flux in the ternary system BaO-B2O3-Na2O. The growth temperature is below the α → β phase transition temperature. The conditions necessary for growing α-BaB2O4 crystals under metastable conditions are determined and the morphology and optical quality of the crystals grown are investigated. [ABSTRACT FROM AUTHOR]

High-quality single crystals of the high-temperature phase of barium metaborate (α-BaB2O4) up to 100–120 g in weight are grown from a flux in the ternary system BaO-B2O3-Na2O. The growth temperature is below the α → β phase transition temperature. The conditions necessary for growing α-BaB2O4 crystals under metastable conditions are determined and the morphology and optical quality of the crystals grown are investigated. [ABSTRACT FROM AUTHOR]

Results of numerical experiments on focusing of a monochromatic spherical wave by a system of two linear zone plates are reported. Calculations were performed for a photon energy of 12.3985 keV and zone plates with a radius of the first zone of 5 μm, a number of zones of 628, and an aperture of 250 μm. To calculate the Kirchhoff integrals, the double Fourier transform method was used and the fast Fourier transform procedure on a grid with a number of points 65 536 = 216 was applied. On the basis of the calculation results, a conclusion was drawn that two zone plates operate as one with a doubled phase shift in zones with a material if the longitudinal distance between them is smaller than 1/3 of the focus depth and the transverse displacement is smaller than 1/3 of the outermost zone width (the focus size). If the distance (displacement) exceeds the focus depth (size), the two zone plates operate independently, similar to refracting lenses with a set of different focusing orders, including the zero order. The nature of the moiré pattern at a transverse displacement of the zone plates is discussed. [ABSTRACT FROM AUTHOR]

The crystal structure of the dioctahedral celadonite mica 1M (space group C2/m; R, 2.98%; 184 unique reflections) is refined from the oblique-texture electron diffraction patterns obtained with the use of imaging plates. The maximum characterizing the location and potential of the hydrogen atom of the hydroxyl group oriented into the unoccupied trans octahedron at an angle of 4.4° with respect to the ab plane is revealed from the difference Fourier-potential syntheses. The O–H interatomic distance is equal to 0.98 Å. The superstructure reflections observed in the selected-area electron diffraction patterns for a number of particles arise from the superposition of two cells, namely, the main cell with a broken base-centered symmetry and the base-centered supercell with the triple parameter a. These reflections are caused by the ordered distribution of the trivalent and divalent cations Fe and Mg over the octahedral cis positions. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]