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The shear of a crystalline interface by a matrix dislocation is an elementary phenomenon of plasticity that generates a three-dimensional elastic field difficult to express. However, in the case of a flat interface and two elastic isotropic media, the present work shows that this field can be described starting from an explicit form of the Green tensor associated with a point force exerted in one of the crystals. Indeed, the knowledge of this tensor makes it possible to express the displacement field of a dislocation in the final form of a surface integral. Because the shear is limited by a matrix branch and an interfacial branch, the dislocation can be called 'hybrid dislocation' or HD. If the two branches are straight, the field is that of an angular HD. Moreover, if the crystals are identical, the field becomes that of an angular matrix dislocation whose field is well known since Yoffe (1960). By applying the superimposition theorem, it becomes possible to determine the field of more complex configurations, such as those sometimes observed during the transmission of the plastic slip through the interfaces. [ABSTRACT FROM AUTHOR]

The transfer of plastic sliding through a crystalline interface involves at least a dislocation having a branch in each crystal. The elastic field associated with this elemental configuration has been processed in the past by Belov et al. (1983, 1992) but has never been verified or used, to the author's knowledge. With typographical corrections and various verifications, the results obtained in this work confirm the validity of the theory for isotropic and/or anisotropic crystals. A general explicit solution to the elastic field is derived in the case of two different isotropic crystals. The theory fails when one branch is along the interface while the other lies in a crystal (hybrid dislocation). On the other hand, if a branch is very little inclined relative to the interface (quasi-hybrid dislocation), the theory applies fully. In this context, the combination of two quasi-hybrid dislocations solves in practice the problem of the triple node anchored to the interface. [ABSTRACT FROM AUTHOR]

The location of the liquidus in the low-pressure crystalline phase of SnI4 was determined utilizing in situ x-ray diffraction measurements under pressures up to approximately 3.5 GPa. The liquidus is not well fitted to a monotonically increasing curve such as Simon's equation, but breaks near 1.5 GPa and then becomes almost flat. The results are compared to those from molecular dynamics simulations. Ways to improve the model potential adopted in the simulations are discussed. [ABSTRACT FROM AUTHOR]

Polycrystalline AgNd(WO[sub 4])[sub 2] has been prepared by a in solid-state reaction. X-ray diffraction measurements indicate that this compound crystallizes with a scheelite-type tetragonal structure. Absorption and emission spectra have been measured, using the technique of the crystal field parameters, to obtain the energy levels scheme for Nd[sup 3+] ions in the crystalline matrix. These data indicate the existence of a structural local disorder associated with a random distribution of the ions of Ag[sup +] and Nd[sup 3+]. The temperature variation of the paramagnetic susceptibility in the range from 2 to 300 K has been studied. The Van Vleck formula has been used to calculate the temperature variation of the paramagnetic susceptibility and it was compared with the experimental results. Particularly at low temperatures, satisfactory agreement has been obtained. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect in single crystalline Nd0.5Sr0.5MnO3 (NSMO 0.5) is investigated by computing the field dependent entropy change (ΔS) and adiabatic temperature change (ΔTad). At the charge ordering temperature (TCO), the value of ΔSmax is found to be much higher than ΔSmax reported in polycrystalline samples. This “giant” entropy change is attributed to interplay (stronger in single crystals) among spin, charge, lattice, and orbital degrees of freedom resulting in a field induced transition at TCO. In contrast, the change in entropy associated with Curie temperature (TC) is very low. The direct measurements of the field induced temperature change (ΔT) are in agreement with the computed value of ΔS. The presence of short-range correlations with charge/orbital order (COO) above and below TC may be responsible for the suppression of the negative MCE at TC. A critical exponent analysis of the paramagnetic (PM) to ferromagnetic (FM) transition using magnetization data yields mean-field-like values, which is likely to be operative in inhomogeneous systems such as NSMO 0.5 with correlated COO clusters larger than lattice parameter. [ABSTRACT FROM AUTHOR]

We study both experimentally and theoretically the dynamics of chemically self-propelled Janus colloids moving atop a two-dimensional crystalline surface. The surface is a hexagonally close-packed monolayer of colloidal particles of the same size as the mobile one. The dynamics of the self-propelled colloid reflects the competition between hindered diffusion due to the periodic surface and enhanced diffusion due to active motion. Which contribution dominates depends on the propulsion strength, which can be systematically tuned by changing the concentration of a chemical fuel. The mean-square displacements (MSDs) obtained from the experiment exhibit enhanced diffusion at long lag times. Our experimental data are consistent with a Langevin model for the effectively two-dimensional translational motion of an active Brownian particle in a periodic potential, combining the confining effects of gravity and the crystalline surface with the free rotational diffusion of the colloid. Approximate analytical predictions are made for theMSDdescribing the crossover from free Brownian motion at short times to active diffusion at long times. The results are in semi-quantitative agreement with numerical results of a refined Langevin model that treats translational and rotational degrees of freedom on the same footing. [ABSTRACT FROM AUTHOR]

Investigations of multifunctional R Al 3 (BO 3 ) 4 ( R = Y, Pr, Sm–Lu) crystals are divided into three stages: 1962–1972, 1972–1990, 1990 to present, and reviewed step by step. Selective and predominantly unpublished results on high-temperature flux growth (mostly by solution growth on dipped seeds, abbreviated as SGDS method) of these bulk (three-dimensional) crystals and their solid solutions, performed by the author’s research group during last decades, are shortly summarized as well. The pursued studies can be considered as a key base for development of highly efficient optical and new laser systems. [ABSTRACT FROM AUTHOR]

Three families of ZnTe magic-sized nanoclusters (MSNCs) were obtained exclusively using polytellurides as a tellurium precursor in a one-pot reaction by simply varying the reaction temperature and time only. Different ZnTe MSNCs exhibit different self-assembling or aggregation behavior, owing to their different structure, cluster size, and dipole--dipole interactions. The smallest family of ZnTe MSNCs (F323) does not reveal a crystalline structure and as a result assembles into lamellar triangle plates. Continuous heating of as synthesized ZnTe F323 assemblies resulted in the formation of ZnTe F398 MSNCs with wurzite structure and concomitant transformation into lamellar rectangle assemblies with the organization of nanoclusters along the <002> direction. Further annealing of ZnTe F398 assembled lamellar rectangles leads to full organization of MSNCs in all directions and formation of larger ZnTe F444 NCs that spontaneously form ultrathin nanowires following an oriented attachment mechanism. The key step in control over the size distribution of ZnTe ultrathin nanowires is, in fact, the growth mechanism of ZnTe F398 MSNCs; namely, the step growth mechanism enables formation of more uniform nanowires compared to those obtained by continuous growth mechanism. High yield of ZnTe nanowires is achieved as a result of the wurzite structure of F398 precursor. Transient absorption (TA) measurements show that all three families possess ultrafast dynamics of photogenerated electrons, despite their different crystalline structures. [ABSTRACT FROM AUTHOR]

The topological crystalline insulator SnTe has been grown epitaxially on a Bi2Te3 buffer layer by molecular beam epitaxy. In a 30-nm-thick SnTe film, p- and n-type carriers are found to coexist, and Shubnikov-de Haas oscillation data suggest that the n-type carriers are Dirac fermions residing on the SnTe (111) surface. This transport observation of the topological surface state in a p-type topological crystalline insulator became possible due to a downward band bending on the free SnTe surface, which appears to be of intrinsic origin. [ABSTRACT FROM AUTHOR]

The article discusses a study which observed actuated conformational switching phenomenon taking place in a single crystal of a homodithiacalix[4]arene. The study introduced diatomic hetera bridges in the macrocyclic ring, in this case disulfide. The study explained that cooperative molecular motion is much more easily achieved for frameworks than in molecular crystals.

The presence of crystalline inclusions in plasma cell myeloma is a rare phenomenon and cases have been reported with rod, needle, and rectangular shaped crystals. Here, we present a case of IgG lambda restricted plasma cell myeloma with rhomboid shaped intracellular crystalline inclusions and extracellular crystal depositions in the bone marrow. Since rhomboid crystal depositions can be seen in other clinical conditions such as pseudogout, this case invites consideration of plasma cell myeloma in the differential diagnosis of patients with rhomboid crystalline deposition in the bone marrow and in sites/organs other than the bone marrow. [ABSTRACT FROM AUTHOR]

Progress in experimental methods of serial sectioning and orientation determination opens new opportunities to study inter-crystalline boundaries in polycrystalline materials. In particular, macroscopic boundary parameters can now be measured automatically. With sufficiently large data sets, statistical analysis of interfaces between crystals is possible. The most basic and interesting issue is to find out the probability of occurrence of various boundaries in a given material. In order to define a boundary density function, a model of uniformity is needed. A number of such models can be conceived. It is proposed to use those derived from an assumed metric structure of the interface manifold. Some basic metrics on the manifold are explicitly given, and a number of notions and constructs needed for a strict definition of the boundary density function are considered. In particular, the crucial issue of the impact of symmetries is examined. The treatments of homo- and hetero-phase boundaries differ in some respects, and approaches applicable to each of these two cases are described. In order to make the abstract matter of the paper more accessible, a concrete boundary parameterization is used and some examples are given. [ABSTRACT FROM AUTHOR]

A scintillating crystal's surface reflectance has to be well understood in order to accurately predict and optimize the crystal's light collection through Monte Carlo simulations. In this paper, we measure the inner surface reflectance properties for BGO. The measurements include BGO crystals with a mechanically polished surface, rough-cut surface, and chemically etched surface, and with various reflectors attached, both air-coupled and with coupling compound. The measurements are performed with a laser aimed at the center of a hemispherical shaped BGO crystal. The hemispherical shape eliminates any non-perpendicular angles for light entering and exiting the crystal. The reflected light is collected with an array of photodiodes. The laser can be set at an arbitrary angle, and the photodiode array is rotated to fully cover 2ir of solid angle. The current produced in the photodiodes is readout with a digital multimeter connected through a multi-plexer. The two rows of photodiodes achieve 5-degree by 4-degree resolution, and the current measurement has a dynamic range of 105 : 1. The acquired data was not described by the commonly assumed linear combination of specular and diffuse (Lambertian) distributions, except for a very few surfaces. Surface roughness proved to be the most important parameter when choosing crystal setup. The reflector choice was of less importance and of almost no consequence for rough-cut surfaces. Pure specular reflection distribution for all incidence angles was measured for polished surfaces with VM2000 film, while the most Lambertian distribution for any surface finish was measured for titanium dioxide paint. The distributions acquired in this paper will be used to create more accurate Monte Carlo models for light reflection distribution within BGO crystals. [ABSTRACT FROM AUTHOR]

Thin films of doped semiconducting barium-strontium titanate (Ba,Sr)TiO3 are prepared by pulsed laser ablation. It is shown that the crystal structure, morphology, and electrical properties of (Ba,Sr)TiO3 thin films are determined primarily by the actual ablation conditions. The ablation regimes of deposition permitting preparation of uniform polycrystalline thin films with a composition close to that of the target and with grain sizes larger than 0.1 μm are established. These samples have a positive temperature coefficient of resistance in the phase transition region. The change in the resistivity can be as much as 100%. [ABSTRACT FROM AUTHOR]

The dissociation of CO serves both as a model test reaction on single crystals and as a relevant reaction step for industrial methanation. We combined extensive density functional theory calculations, ultra-high vacuum experiments on well-defined single crystals, and catalytic activity measurements on supported catalysts in a study of the dissociation mechanism of CO on Ni surfaces. We found that this process is highly structure-sensitive and also is sensitive to the presence of hydrogen: Under ultra-high vacuum, with no hydrogen present, the dissociation proceeds through a direct route in which only undercoordinated sites (e.g., steps) are active. Under methanation conditions, the dissociation also proceeds most favorably over undercoordinated sites, but through a COH species. [Copyright &y& Elsevier]

Abstract: We have realized highly oriented nitride-based α-Fe/AlN/Fe3N ferromagnetic hybrid structures on Si(111) substrates by molecular beam epitaxy using AlN/SiC intermediate layers. A two-step hysteresis loop, typically observed in magnetic tunneling junctions, was clearly observed in magnetization versus magnetic field measurements. This result indicates the formation of ferromagnetic α-Fe and Fe3N layers separated by 8-nm-thick AlN layers over approximately 1cm2 area, and also shows the difference in coercive field between the two ferromagnetic layers. [Copyright &y& Elsevier]

Both the approach used and the progress made in the assignment of structure types to the crystal structures contained in the ICSD database are reported. Extending earlier work, an hierarchical set of criteria for the separation of isopointal structures into isoconfigurational structure types is used. It is shown how these criteria, which include the space group (number), Wyckoff sequence and Pearson symbol, c/ a ratio, β ranges, ANX formulae and, in certain cases, the necessary elements and forbidden elements, may be used to uniquely identify the representative structure types of the compounds contained in the ICSD database. [ABSTRACT FROM AUTHOR]

Abstract: The thermodynamic modelling of solid (crystalline) phases forms a central topic within the Calphad approach and a variety of aspects have been discussed at previous Ringberg workshops. At the present Ringberg workshop, modelling of volume and its temperature, pressure and composition dependence formed a major part of the discussions. In addition, modelling of the heat capacity above the (equilibrium) melting temperature, sublattice modelling of complex phases, modelling of ordering and interstitial solutions in the bcc lattice and the effect of magnetism were addressed. [Copyright &y& Elsevier]

We present an overview of friction processes expected between two ideal crystals of strong layers (graphite, MoS2, etc.) when one crystal is rotated with respect to the other by a certain angle θ. We assume perfect conditions: no impurities; no preexisting dislocations in the bulk of the crystals; slow gliding velocities. Two regimes show up: (a) Weak coupling when , where are typical intra- (inter-) layer interactions. Here we expect weak friction, controlled by two-phonon processes, and analyzed by Sokoloff et al. However, we point out that surface waves at the interface also play a role. (b) Strong coupling () where two orthogonal sets of screw disclinations should build up in the contact plane, as shown long ago by F.C. Frank. Here (to a first approximation) the dislocations are arranged in ladders, and we expect solid friction with a Peierls–Nabarro threshold stress. [ABSTRACT FROM AUTHOR]

The article refers to brittle nanocrystalline materials and the activity of catastrophic merging in them. For this, a model has been proposed that is based on the percolation theory. For intensive experimental and theoretical studies, nanocrystalline materials with unique mechanical properties are considered.

Molecular dynamics simulations are carried out to analyze the structure and mechanical behavior of Cu nanowires with lateral dimensions of 1.45-2.89 nm. The calculations simulate the formation of nanowires through a "top-down "fabrication process by "slicing" square columns of atoms from single-crystalline bulk Cu along the [001], [010], and [100] directions and by allowing them to undergo controlled relaxation which involves the reorientation of the initial configuration with a ...001... axis and {100} surfaces into a new configuration with a ...110... axis and {111} lateral surfaces. The propagation of the planes is primarily responsible for the lattice rotation. The transformed structure is the same as what has been observed experimentally in Cu nanowires. A pseudoelastic behavior driven by the high surface-to-volume ratio and surface stress cit the nanoscale is observed for the transformed wires. Specifically, the relaxed wires undergo a reverse transformation to recover the configuration it possessed as part of the bulk crystal prior to relaxation wizen tensile loading with sufficient magnitude is applied. The reverse transformation progresses with the propagation of a single twin boundary in reverse to that observed during relaxation. This process has the diffusionless nature and the invariant-plane strain of a martensitic transformation. and is similar to those in shape memory alloys in phenomenology. The reversibility of the relaxation and loading processes endows the nanowires with the ability for pseudoelastic elongations of up to 41% in reversible axial strain which is well beyond the yield strain of the approximately 0.25% of bulk Cu and the recoverable strains on the order of 8% of most bulk shape memory materials. The existence of the pseudoelasticity observed in the single-crystalline, metallic nanowires here is size and temperature dependent. At 300 K, this effect is observed in Wires with lateral dimensions equal to or smaller than 1.81 × 1.81 nm. As temperature increases, the critical wire size for observing this effect increases. This temperature dependence gives rise to a novel shape memory effect to Cu nanowires not seen in bulk Cu. [ABSTRACT FROM AUTHOR]

This is a critical survey of the phenomenon of strain-induced crystalline phase changes in semi-crystalline polymers. This paper is not concerned with the strain induced crystallization of glassy polymers. An examination is made of the experimental data reported in literature, together with a discussion about the mechanism of crystalline phase transitions and about the benefits or prejudices which result on the materials properties. Special attention has been paid to the most largely documented polymers which include materials having either van der Waals, or hydrogen or polar interchain bonding. This concerns polypropylene, polyamide 6, ethylene/vinyl-alcohol copolymers, poly(vinylidene fluoride) polyesters, and polyethylene. An additional section is devoted to several series of much less documented polymers, from the standpoint of crystal phase changes. Although most of the cases are dealing with films and fibers submitted to tensile drawing, some of the reported studies are concerned with bulk materials. An attempt is made to establish guidelines for the mechanisms of crystalline phase changes based on chain conformation, thermodynamic stability, and plasticity defects. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure of the new ternary compound TmCu4−x Sb2 (x =1.065) was determined by direct methods from X-ray powder data (diffractometer DRON-3M, Cu Kα-radiation). It crystallizes with the orthorhombic structure type ErFe4Ge2 (low-temperature modification) and is the first representative of this structure type among known antimonides: space group Pnnm, Pearson code oP14-2.13, a =7.00565(6)Å, b =7.83582(6)Å, c =4.25051(3)Å, Z =2. Investigated structure is an orthorhombically deformed derivative of the ZrFe4Si2 structure type. [Copyright &y& Elsevier]

Extensive theoretical analysis and experimental observations show surface roughening transitions of crystals. The surface roughening is characterized by step free energy, which gradually decreases to 0 at the roughening transition temperature. For a crystal of finite size, the surface roughening transition is manifested by gradual increase of the curved edge and corner areas. In alloys, the interfaces between the solid and the liquid phases can be either singular, partially rough, or completely rough at different temperatures. Their thermally induced roughening transitions are similar to those of the solid-vapor interfaces. The interface roughening and the reverse transition to singular structures can also be induced by additives. The grain boundaries of any misorientation angles in oxides and metals also show roughening transitions. The singular grain boundaries have either flat, hill-and-valley, or kinked shapes, and with temperature increase or composition changes, they become defaceted to curved shapes. These defaceted grain boundaries are rough. It is thus possible to produce either singular or rough grain boundaries by heat-treatment or additives to vary their properties. [ABSTRACT FROM AUTHOR]

Abstract: . A crystalline interface is often covered by a dense network of linear defects with a (pseudo) biperiodic geometry. The elastic field of this network is calculated by thinking the interface as paved by adjacent Somigliana dislocations. The analysis of a portion of an erratic zigzag line of a (001)Si low angle twist boundary, observed in two-beam transmission electron microscopy, is given as an example. To cite this article: A. Boussaid et al., C. R. Physique 6 (2005). [Copyright &y& Elsevier]

A model is proposed for metastable DX centers formed through Jahn–Teller distortion of the crystal lattice of cadmium telluride, i.e., through the displacement of a DCd residual donor impurity atom (where D is a Group III element of the periodic table) to the region of a nearest neighbor interstice. The configuration-coordinate diagram for a VCd–Di associated defect is constructed with due regard for the tetrahedral and hexagonal positions of interstitial atoms. The Stokes shift, n-type conductivity, location of the Fermi level, specific features of photoluminescence, and some other effects are explained in terms of the configuration-coordinate diagram. The results of experimental investigations of the energy spectrum of DX centers in cadmium telluride single crystals are in agreement with available theoretical data. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The parameters of hyperfine interactions in Pb3+F–8F–a tetragonal clusters of MeF2 crystals (Me = Ca, Sr, Ba) are interpreted. The contributions of the spin polarization to the parameters of the proper hyperfine interaction and additional (ligand) hyperfine interactions are calculated in the approximation of weak binding between a charge-compensating ion F–a and a cubic fragment in the tetragonal cluster. It is demonstrated that correct inclusion of the contributions from the spin polarization to the ligand isotropic hyperfine interaction for the F–a ion leads to anomalously large parameters of this interaction for MeF2 crystals. These results are in agreement with experimental data. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The structure of an amorphous Ge layer near an interface with a Si(111) crystal was studied by quantitative high-resolution electron microscopy. It was found that the translational symmetry of a Si crystal leads to the crystal-like order in the positions of Ge atoms in the interfacial region, the width of which is about 1.4 nm. In this region, the average orientation of interatomic bonds tilted with respect to the interface compensates for the difference in the bond lengths in crystalline Si and amorphous Ge and is responsible for the tetragonal distortion of the most likely atomic positions. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The general formulation of double refraction or internal double reflection with different directions of propagation vector and wave vector in a uniaxial crystal is analysed in terms of Huygens' principle. Then double refraction and double reflection along the sequential interfaces in a crystal are discussed. On this basis, a configuration of electro-optic 1× N optical switch with modulators and birefringent crystal slabs integrated in a single block of crystal is suggested, which is simple and compact in construction, low in loss and insensitive to environment. Finally, calculations are given which lead to a proposed design of a 1×4 switch. [ABSTRACT FROM AUTHOR]

Reports on the detailed comparison of the one-dimensional paracrystalline and perturbed lattice models of disordered crystals and their diffraction. Calculation of diffraction patterns showing that with an appropriate choice of parameters, the two models give essentially identical diffraction for small crystallites and very similar diffraction for larger crystallites.

We use atomistic simulations to investigate the interaction of vacancies and interstitials with interfaces between a crystalline metal and an amorphous, covalently-bonded solid. We select the gold (Au)/silicon (Si) binary system as a model material and construct interface models along two different facets of crystalline Au and with amorphous Si (a-Si) created at three different quench rates. We compute formation energies of vacancies, self-interstitials, and interstitial impurities as a function of position relative to the interface and find that they have markedly lower values near the interface than in the interior of the adjoining phases. We conclude that crystal/amorphous, metal/covalent interfaces may be as effective at removing radiation-induced point defects as interfaces in polycrystalline metals composites. Moreover, irrespective of interface character, the average formation energies of all point defects at all the Au/a-Si interfaces we investigated are comparable. Thus, unlike in polycrystalline metals, where an interface's crystallographic character has a marked effect on its interactions with point defects, all interface types in crystal/amorphous, metal/covalent composites may be equally effective at absorbing all radiation-induced defects. • Atomistic models of crystalline gold (Au)/amorphous silicon (Si) interfaces are developed. • Formation energies of vacancies, and interstitials are markedly lower near the interface than inside the adjoining phases. • Irrespective of interface character, the formation energies of all point defects at Au/a-Si interfaces are nearly identical. • Interfaces between crystalline metals and amorphous covalently bonded solids are effective sinks for point defects. [ABSTRACT FROM AUTHOR]

The piezoelectric properties of [001]c poled 0.94Pb(Zn1/3Nb2/3)O3–0.06PbTiO3 single crystals were greatly enhanced by controlling their domain configurations. Contrary to the interpretation of charged domain walls being the main contributor to the piezoelectric enhancement, we found that smaller domain size and more neutral domain walls were the main contributors for the piezoelectric enhancement of these multidomain crystals. The properties of 109° neutral domain walls in 0.94Pb(Zn1/3Nb2/3)O3–0.06PbTiO3 single crystals were extracted by using a piezoelectric domain wall model. [ABSTRACT FROM AUTHOR]

Phase composition and molecular mobility were studied using 1H NMR T 2 relaxometry in isotactic polybutene-1 (iPB-1) with two polymorphs - form I and II crystals. Several types of NMR relaxation methods and data analysis were evaluated for determining the most reliable way for studying physical phases in iPB-1. Three-phase model provided the most appropriate description of the phase composition in iPB-1, i.e., a crystal-amorphous interface separates the crystalline and the amorphous phases. Due to complex molecular mobility in iPB-1, the amount of rigid fraction should be considered as NMR crystallinity number. Two types of chain segments are present in the amorphous phase: (1) chain segments with anisotropic mobility due to chain anchoring to crystals and chain entanglements; and (2) highly mobile chain end segments. The polymorphic phase II to I transition causes significant immobilization of polymer chains in the crystalline and the amorphous phases. Molecular weight of iPB-1 largely influences phase composition and molecular mobility in crystalline and amorphous phases. Image 1 • Phase composition and molecular mobility in isotactic polybutene-1 are studied using 1H NMR T 2 relaxometry. • The three-phase model provides the best description of the phase composition. • Advantages and disadvantages of different types of T 2 relaxation experiments are discussed. • The polymorphic phase II to I transition causes decrease in chain mobility in the crystalline and the amorphous phases. • Molecular weight of iPB-1 largely influences phase composition and molecular mobility in crystalline and amorphous phases. [ABSTRACT FROM AUTHOR]

First-principles calculations of the atomic and electronic structure of crystalline CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) are performed to understand the effect of B on spin-dependent transport in these junctions. The authors find that it is energetically favorable for B atoms to reside at the crystalline CoFeB/MgO interface rather than remain in the bulk of the crystalline CoFeB electrode. The presence of B at the interfaces is detrimental to tunneling magnetoresistance (TMR) because it significantly suppresses the majority-channel conductance through states of Δ1 symmetry. Preventing B segregation to the interfaces during annealing should result in an enhanced TMR in CoFeB/MgO/CoFeB MTJs. [ABSTRACT FROM AUTHOR]

Different types of waveguides and connections between them were fabricated in a three-dimensional (3D) layer-by-layer photonic crystal. The waveguides were formed by removing either a single rod or a series of rod fragments running in three mutually orthogonal directions. This provides the potential of forming a 3D network of waveguide channels with cross sectional dimensions on the order of one lattice constant. The propagation behavior of guided modes in these waveguide networks was probed using a network analyzer. High transmission efficiency (with loss below 0.5 dB) through various waveguide bends and networks with carefully designed geometries has been achieved. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The band structure of the TlGaTe2 compound is calculated by the pseudopotential method. The spectral dependences of the real and imaginary parts of the complex permittivity are determined in the case when the polarizations are parallel and perpendicular to the optic axis of the crystal. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

We demonstrate the use of Raman spectroscopy with a multichannel detector to characterize the growth of PtSi on Si(100). The vibrational modes of surface silicide layers as thin as 10 Å and PtSi layers less than 40 Å thick buried under 140 Å of Pt have been observed without the need for any special sample geometry for signal enhancement. The Raman spectra can identify the silicide layer, estimate its thickness, and demonstrate its crystalline quality. This can be done on an arbitrary substrate, in air and without any special sample preparation. [ABSTRACT FROM AUTHOR]

The article describes a method for the generation of relief features with vertical dimensions ranging from the micro scale to the atomic scale using partially fractured, single-crystalline silicon substrates. The generation of cracks using this procedure is straightforward and high yielding. The wide availability of high-quality Silicon wafers and the ease of generation of the crack and step make this approach attractive for wide use in nanoscience. This type of method, accurate, quick, and inexpensive, is attractive because it is highly accessible to the general scientific community.

Models consisting of chains of particles that are coupled to their neighbours appear in many applications in physics or engineering, such as in the study of dynamics of mono-atomic and multi-atomic lattices, the resonances of crystals with impurities and the response of damaged bladed discs. Analytical properties of the dynamic responses of such disturbed chains of identical springs and masses are presented, including when damping is present. Several remarkable properties in the location of the resonances (poles) and anti-resonances (zeros) of the displacements in the frequency domain are presented and proved. In particular, it is shown that there exists an elliptical region in the frequency-disturbance magnitude plane from which zeros are excluded and the discrete values of the frequency and disturbance at which double poles occur are identified. A particular focus is on a local disturbance, such as when a spring or damper is modified at or between the first and last masses. It is demonstrated how, notably through normalization, the techniques and results of the paper apply to a broad category of more complex systems in physics, chemistry and engineering. [ABSTRACT FROM AUTHOR]

The article presents a perspective on the experiments on microfractures in crystals. According to the author, researchers found in preliminary experiments spurious signals and bursts of energy with unlikely signatures. He added that researchers have later found out that they were seeing traces of microfracture events in sapphire crystal.

In the mol­ecule of the title compound, C28H23N3O2, the nitro group is almost perpendicular to the carbazole ring to which it is attached. The crystal packing is determined by C—H⋯O and π–π inter­actions, where the nitrated carbazole ring of one mol­ecule associates in a shifted parallel planar orientation with the centrosymmetrically related non-nitrated carbazole ring of a neighbouring mol­ecule. [ABSTRACT FROM AUTHOR]