Crystal Channels Research Articles

Calculation of cation migration channels in crystals with sсheelite-type structures

Calculation of cation migration channels in crystals with sсheelite-type structures

Structural features of gem minerals and identification and evaluation

Gem has long been chased because of its cultural and historical significance and beauty, and the identification and evaluation of its structural features have also been paid attention to. Plum blossom jade and emerald were identified and analyzed by means of the conventional detection method, infrared spectroscopy and X-ray powder diffraction analysis. The results showed that plum blossom jade with black and brown background and red, white and brown amygdaloid body spots had a diameter of 1-10 mm, a relative density of 2.69-2.75 g/cm3 and a refractive index of 1.52-1.55, and its minerals contained water molecules, quartz, low albite, anorthoclase and andesite. It was observed that emerald was green, greasy, glassy, transparent, with a relative density of 2.66-2.78 g/cm3 and 1.58 refractive index, and its minerals contained water molecules; there were two kinds of arrangement in crystal channels. The main mineral component of emerald was beryl, and its purity was high.

A high performance electroformed single-crystallite VO2 threshold switch.

Threshold switches (TSs) are an effective approach for resolving the sneak path problem within a memristor array. VO2 is a promising material for fabricating high-performance TSs. Here we report a single crystal VO2-based TS device with high switching performance. The single crystal monoclinic VO2 channel is obtained by electroforming in a composite vanadium oxide film consisting of VO2, V2O5 and V3O7. The formation mechanism on single crystal VO2 is thoroughly investigated by means of X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The single crystal VO2-based TS device exhibits better switching performance than the polycrystalline monoclinic VO2 counterpart. The TS device based on a single crystal channel with the (2[combining macron]11) orientation exhibits a steep turn-on voltage slope of <0.5 mV dec-1, a fast switching speed of 23 ns, an excellent endurance over 109 cycles, a high Ion/Ioff ratio of 143 and a low sample-to-sample variance. The enhanced switching performance originates from the single crystal feature and specified crystal orientation.

Сдвиговой режим формирования градиента температуры в тонком нематическом канале

AbstractIt has been shown by means of numerical methods, in the framework of the classical Ericksen-Leslie theory, together with accounting the entropy balance equation, how a temperature gradient, in the initially uniformly heated a hybrid-oriented liquid crystal (HOLC) channel, may set up under action of a shear stress (SS). The cases of complete and partial thermal insulation of one of the boundary surfaces of the HOLC are analyzed under the condition that a constant temperature is kept on the rest boundaries. It also has been shown how to heat up the planarly oriented upper boundary of the HOLC channel under the influence of the SS and, thereby, to form the temperature gradient across the HOLC channel.

Термомеханический режим формирования вихревых течений в гибридно ориентированном нематическом канале

AbstractIn this paper, we described numerically several scenarios of formation of vortex flows (VF) in microsized hybrid-oriented liquid crystal (HOLC) channels with orientation defects using a nonlinear generalization of the classical Ericksen–Leslie theory that allows taking into account termomechanical contribution, both in the expression for the shear stress and in the entropy balance equation. An analysis of the numerical results showed that there are two or one vortices in the HOLC channel although two vortices directed towards each other are generated at the initial stage of the VT formation Thermomechanically Excited Vortical Flow.

Plasmon-mediated discrete diffraction behaviour of an array of responsive waveguides.

We investigate the discrete diffraction phenomenon in a Polymer-Liquid Crystal-Polymer Slices (POLICRYPS) overlaying a random distribution of gold nanoparticles (AuNPs, plasmonic elements). We study the propagation of a CW green laser beam through the waveguide structure as a function of beam polarization, laser intensity and sample temperature. It turns out that the plasmonic field created at the interface between AuNPs and POLICRYPS waveguides enables and stabilizes the optical field propagation within the responsive nematic liquid crystal channels. The active role of the liquid crystal is pointed out by a polarization, temperature and beam divergence experimental analysis and evidenced by a peculiar trumpet-shaped discrete diffraction pattern. Theoretical simulations confirm that the observed optical behavior is governed by the interaction of the nematic liquid crystal with optical and plasmonic fields.

Explaining water adsorption in one-dimensional channels in AlPO4-5 on molecular scale

Abstract The adsorption of water in one-dimensional channels in porous aluminophosphate material AlPO4-5 has been studied by a combination of gravimetric analysis techniques, neutron and X-ray diffraction and neutron spectroscopy. Molecular structure of AlPO4-5 consists of 12-membered rings of alternating, corner-sharing AlO4 and PO4 tetrahedra connected by oxygen bridges into sheets in the (a, b) plane. The sheets are connected by oxygen bridges along the c crystal axis and form one-dimensional channels of which the largest, formed by the 12-membered rings, have a van der Waals diameter of about 8.3 A. Gradually increasing the amount of adsorbed water we could follow the evolution of the confined water mobility in a systematic way and identify the molecular mechanism of water adsorption. We focused particularly on the range of low and medium relative pressures up to p/p0 = 0.32, where a change from a hydrophobic behavior to a steep, capillary condensation like water intake has been observed. At the initial adsorption stages water occupies positions close to the pore walls causing the contraction of channels in the (a, b) plane and the prolongation of the channels along c axis in AlPO4-5. With the progressing intake water molecules form chains along the main channels. The cooperative interactions between water molecules lead to the onset of phonon-like cooperative modes and, surprisingly, to the increase of diffusive-like motion, which slow down only in the final adsorption stages when AlPO4-5 channels are completely filled.

Synthesis and Reversible Hydration of a Pseudoprotein, a Fully Organic Polymeric Desiccant by Multiple Single-Crystal-to-Single-Crystal Transformations.

A diphenylalanine derivative, N3-Phe-Phe-NHCH2CCH, was designed for topochemical azide-alkyne cycloaddition (TAAC) polymerization. This dipeptide adopted β-sheet arrangement as designed, in its crystals, but the azide and alkyne were not fitly aligned for their topochemical reaction. However, the voids present around these groups allowed them to attain a reactive geometry upon heating and their consequent TAAC polymerization to a pseudoprotein in a single-crystal-to-single-crystal (SCSC) fashion. This motion led to the creation of channels in the product crystal and it absorbed water from the surroundings to fill these channels as H-bonded water wire. The pseudoprotein undergo reversible hydration/dehydration in SCSC fashion many times under mild conditions: hydration at low relative humidity and dehydration at low temperature. Vapor sorption analyses suggest that this fully organic polymer might be useful as an energy-efficient desiccant material for controlling indoor humidity.

Synthesis and Reversible Hydration of a Pseudoprotein, a Fully Organic Polymeric Desiccant by Multiple Single‐Crystal‐to‐Single‐Crystal Transformations

AbstractA diphenylalanine derivative, N3‐Phe‐Phe‐NHCH2CCH, was designed for topochemical azide–alkyne cycloaddition (TAAC) polymerization. This dipeptide adopted β‐sheet arrangement as designed, in its crystals, but the azide and alkyne were not fitly aligned for their topochemical reaction. However, the voids present around these groups allowed them to attain a reactive geometry upon heating and their consequent TAAC polymerization to a pseudoprotein in a single‐crystal‐to‐single‐crystal (SCSC) fashion. This motion led to the creation of channels in the product crystal and it absorbed water from the surroundings to fill these channels as H‐bonded water wire. The pseudoprotein undergo reversible hydration/dehydration in SCSC fashion many times under mild conditions: hydration at low relative humidity and dehydration at low temperature. Vapor sorption analyses suggest that this fully organic polymer might be useful as an energy‐efficient desiccant material for controlling indoor humidity.

Positive features of crystal extraction of protons and carbon ions from the U-70 on basis of long-term experience

Works on the steering of particle beams using channeling in aligned bent crystals have been carried out at IHEP over a number of years. Comprehensive theoretical and experimental studies have led to the creation of actually operating systems on the U-70 accelerator. In particular, a slow proton beam extraction with unprecedentedly high parameters, an extraction efficiency of about 85% at a beam intensity of 10[Formula: see text] particles per cycle, has been realized on U-70 using particle channeling in short bent crystals. In recent years, successful experiments on the extraction of carbon ions were performed. At present, crystal elements are used in regular U-70 runs and provide half of the particle beams for physical experiments. Here, we summarize the results of this unique experience in the world practice of accelerators and outline its prospects.

Orbital angular momentum of channeling radiation from relativistic electrons in thin Si crystal

We propose to use channeling radiation (CR) from relativistic electrons as a source of high energy twisted photons in the MeV range. We calculate numerically the orbital angular momentum (OAM) of radiation produced by electrons with the energies 155÷2500 MeV for the axial and planar channeling in the thin Si crystal. We obtain that the average OAM of CR in this case is approximately 1÷6ħ per photon with the photon energies about 1÷2 MeV.

Application of Crystal Elements for Charged Particle Beam Steering and Radiation Beam Generation on the U-70 Synchrotron

Works on the formation of particle and radiation beams using particle channeling and reflection in oriented crystals have been carried out at IHEP over a number of years. Comprehensive theoretical and experimental studies have led to the creation of actually operating systems on the U-70 accelerator. In particular, a slow proton beam extraction with unprecedentedly high parameters, an extraction efficiency of about 85% at a beam intensity of 1012 particles per cycle, has been realized on U-70 using particle channeling in short bent crystals. Experiments to implement the method of particle reflection in crystals for beam extraction and collimation have been carried out on U-70. At present, crystal elements are used in regular U-70 runs and provide half of the particle beams for physical experiments. We summarize the results of this unique experience in the world practice of accelerators and outline its prospects.

Photophysical properties of cationic dyes captured in the mesoscale channels of micron-sized metal-organic framework crystals

The optical properties of dye molecules in confined spaces can differ from the solution phase due to confinement effects. Pre-organized mesoscale channels of metal-organic frameworks (MOFs) are very suited for hosting various dyes, and the robust frameworks often render the encapsulated dyes with certain preferential geometries, which are different from those found in solution. Furthermore, pre-organized open channels can efficiently guide the uniform and unique spatial distribution of dye molecules in a controlled manner, which are otherwise difficult to achieve. Thus, sufficiently large dye molecules can avoid the formation of complex aggregates when captured inside open channels. In contrast, small dye molecules can form well-defined dimers or aggregates. The resulting dye-encapsulated MOFs can display unusual photophysical properties of the captured dyes. An anionic framework of In-BTB with mesoscale 3D channels is utilized for the efficient encapsulation of various cationic dyes through cation-exchange processes. Six different cationic dyes are encapsulated in the anionic framework of In-BTB, and their crystal structures are completely solved. Novel photophysical properties of these spatially distributed dye molecules in dye@In-BTBs are investigated.

Trapezoid 2D photonic crystal nanoring resonator-based channel drop filter for WDM systems

In the present work, a nanostructure of trapezoid photonic crystal ring resonator-based channel drop filter is designed for wavelength division multiplexing systems (WDM) to drop a channel at a center peak wavelength of 1543 nm. The proposed channel drop filter is composed of bus waveguide, drop waveguide, trapezoid nanoring resonator and reflector in a two-dimensional (2D) hexagonal lattice with circular rods arranged in air host. The trapezoid nanoring resonator is playing a very important role in WDM systems for dropping a single channel over a wide wavelength range. The photonic band gaps of perfect lattice structure and non-perfect lattice structure are absolutely calculated by plane wave expansion method. The functional properties of the designed filter are evaluated by finite difference time domain method (FDTD). The functional properties are center peak wavelength, dropping efficiency, passband width and quality factor. The FDTD method results show dropping efficiency is 100%, and quality factor is about 514.33 which are highly suitable for WDM systems. Further, lattice constant, inner and outer rod radius and refractive index difference of the structure are varied to tune the filter center peak wavelength and its corresponding functional parameters effects are investigated. The proposed nanoring resonator-based optical filter is ultra-compact size around $$14\, \upmu \hbox {m} \times 8.4\, \upmu \hbox {m}$$ ; hence, it is extremely suitable for WDM-based photonic communication systems and photonic integrated circuits.

Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

Hexagonal boron nitride (h-BN) is a layered crystal that is attracting a great deal of attention as a promising material for nanophotonic applications. The strong optical anisotropy of this crystal is key to exploit polaritonic modes for manipulating light-matter interactions in 2D materials. h-BN has also great potential for solid-state neutron detection and neutron imaging devices, given the exceptionally high thermal neutron capture cross section of the boron-10 isotope. A good knowledge of phonons in layered crystals is essential for harnessing long-lived phonon-polariton modes for nanophotonic applications and may prove valuable for developing solid-state 10BN neutron detectors with improved device architectures and higher detection efficiencies. Although phonons in graphene and isoelectronic materials with a similar hexagonal layer structure have been studied, the effect of isotopic substitution on the phonons of such lamellar compounds has not been addressed yet. Here we present a Raman scattering study of the in-plane high-energy Raman active mode on isotopically enriched single-crystal h-BN. Phonon frequency and lifetime are measured in the 80–600-K temperature range for 10B-enriched, 11B-enriched, and natural composition high quality crystals. Their temperature dependence is explained in the light of perturbation theory calculations of the phonon self-energy. The effects of crystal anisotropy, isotopic disorder, and anharmonic phonon-decay channels are investigated in detail. The isotopic-induced changes in the phonon density of states are shown to enhance three-phonon anharmonic decay channels in 10B-enriched crystals, opening the possibility of isotope tuning of the anharmonic phonon decay processes.

Investigation of structure and function of mitochondrial alcohol dehydrogenase isozyme III from Komagataella phaffii GS115

BackgroundAlcohol dehydrogenases (ADHs) catalyze the reversible oxidation of alcohol using NAD+ or NADP+ as cofactor. Three ADH homologues have been identified in Komagataella phaffii GS115 (also named Pichia pastoris GS115), ADH1, ADH2 and ADH3, among which adh3 is the only gene responsible for consumption of ethanol in Komagataella phaffii GS115. However, the relationship between structure and function of mitochondrial alcohol dehydrogenase isozyme III from Komagataella phaffii GS115 (KpADH3) is still not clear yet. MethodsKpADH3 was purified, identified and characterized by multiple biophysical techniques (Nano LC-MS/MS, Enzymatic activity assay, X-ray crystallography). ResultsThe crystal structure of KpADH3, which was the first ADH structure from Komagataella phaffii GS115, was solved at 1.745 Å resolution. Structural analysis indicated that KpADH3 was the sole dimeric ADH structure with face-to-face orientation quaternary structure from yeast. The major structural different conformations located on residues 100–114 (the structural zinc binding loop) and residues 337–344 (the loop between α12 and β15 which covered the catalytic domain). In addition, three channels were observed in KpADH3 crystal structure, channel 2 and channel 3 may be essential for substrate specific recognition, ingress and egress, channel 1 may be the pass-through for cofactor. ConclusionsKpADH3 plays an important role in the metabolism of alcohols in Komagataella phaffii GS115, and its crystal structure is the only dimeric medium-chain ADH from yeast described so far. General significanceKnowledge of the relationship between structure and function of KpADH3 is crucial for understanding the role of KpADH3 in Komagataella phaffii GS115 mitochondrial metabolism.

Crystal implementation in SixTrack for proton beams

Crystal channeling is a property of crystals resulting from the extreme order in which the atoms are arranged: the crystalline lattice. Positive charged particles can get trapped between crystalline planes, and bending highly pure crystals allows deflecting high energy beams. Thus, they are very interesting for applications as primary collimator. The crystals installed in the Large Hadron Collider (LHC) provide a deflection that is equivalent to a magnetic field of about 300 T ideally acting only on halo particles. The implementation of a crystal routine in the framework of the collimation tools used at CERN for simulations of expected beam loss pattern around the entire machine (SixTrack) is therefore mandatory. The crystal routine presented here is suited for high statistics tracking simulations in large hadron accelerators. An introduction to the crystal physics relevant for our purposes is reported, on which the models implemented in the routine are based. Then, the implementation of these models in SixTrack is described.

New experimental discovery of channel crystal plane and orientation selection for small-sized uniaxial strained Si PMOS

The inversion layer mobility of small-sized uniaxial strained Si p-channel metal oxide semiconductor (PMOS) channel is closely related to the crystal plane and crystal orientation. When optimally designing the strained PMOS, the crystal plane and crystal orientation of the channel should be chosen reasonably. At present, there is a theoretical sort model for the inversion layer mobility of Si PMOS channel at 1.5 GPa stress according to the crystal plane and crystal orientation. However, in the actual manufacturing process of device, the process of covering the SiN stress film is fixed, because the channel coefficient of stiffness is aeolotropic. So, the stress intensities of strained PMOS in different crystal planes and orientation channels are different, which causes the theoretical sort model for the inversion layer mobility to be invalid. To solve this problem, the small-sized uniaxial strained Si PMOS and unstrained Si PMOS with different crystal planes and orientations are fabricated by 40 nm technological process of Chinese Academy of Sciences. The result for the inversion layer mobility of Si PMOS channel according to the crystal plane and crystal orientation is obtained by the device transfer characteristic test. Considering the process implementation factors, the relevant conclusion about the inversion layer mobility of small-sized uniaxial strained Si PMOS channel according to the crystal plane and crystal orientation is more suitable to guide the actual device manufacturing than the theoretical sort result predicted in the literature. At the same time, the relevant analysis method can also provide important technical reference for the solution of other strained material MOS.

Energy Spectrum of Relativistic Electrons Channeled Through Single-Wall Carbon Nanotubes

The energy eigenvalues of the channeled electrons through single wall carbon nanotubes (n,m) was calculated. According to the continuum model approximation given by Lindhard for the case of an axial channeling in single crystals, the actual periodic potential of a row of atoms is replaced by a potential averaged over a direction parallel to the row, called continuum potential. The calculations was executed by using the atomic interaction potential as given by Moliere potential. The maximum number of bound states and the energy eigenvalues is calculated for positrons of 100 MeV energy incident in a direction parallel to the nanotube axis, by using WKB method. The calculations showed that the effect of temperature by using Debye approximation of thermal vibration amplitude on the channeling potential is very small and gave the same eigenvalues and the same number of bound states as that for the static nanotubes.

Channeling implantation of high energy carbon ions in a diamond crystal: Determination of the induced crystal amorphization

Abstract This work reports on the induced diamond crystal amorphization by 4 MeV carbon ions implanted in the 〈1 0 0〉 oriented crystal and its determination by application of RBS/C and EBS/C techniques. The spectra from the implanted samples were recorded for 1.2, 1.5, 1.75 and 1.9 MeV protons. For the two latter ones the strong resonance of the nuclear elastic scattering 12C(p,p0)12C at 1.737 MeV was explored. The backscattering channeling spectra were successfully fitted and the ion beam induced crystal amorphization depth profile was determined using a phenomenological approach, which is based on the properly defined Gompertz type dechanneling functions for protons in the 〈1 0 0〉 diamond crystal channels and the introduction of the concept of ion beam amorphization, which is implemented through our newly developed computer code CSIM.