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Crystals, Volume 9, Issue 9 (September 2019)

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Open AccessArticle
The Microalloying Effect of Ce on the Mechanical Properties of Medium Entropy Bulk Metallic Glass Composites
Crystals 2019, 9(9), 483; https://doi.org/10.3390/cryst9090483 (registering DOI) - 15 Sep 2019
Abstract
Novel ultra-strong medium entropy bulk metallic glasses composites (BMGCs) Fe65.4−xCexMn14.3Si9.4Cr10C0.9 and Ti40−xCexNi40Cu20 (x = 0, 1.0), through the martensite transformation induced plasticity (TRIP effect) to [...] Read more.
Novel ultra-strong medium entropy bulk metallic glasses composites (BMGCs) Fe65.4−xCexMn14.3Si9.4Cr10C0.9 and Ti40−xCexNi40Cu20 (x = 0, 1.0), through the martensite transformation induced plasticity (TRIP effect) to enhance both the ductility and work-hardening capability, were fabricated using magnetic levitation melting and copper mold suction via high frequency induction heating. Furthermore, the Ce microalloying effects on microstructure and mechanical behaviors were studied. The Fe-based BMGCs consisted of face-centered cubic (fcc) γ-Fe and body-centered cubic (bcc) α-Fe phase, as well as Ti-based BMGCs containing supercooled B2-Ti (Ni, Cu) and a thermally induced martensite phase B19’-Ti (Ni, Cu). As loading, the TRIP BMGCs exhibited work-hardening behavior, a high fracture strength, and large plasticity, which was attributed to the stress-induced transformation of ε-Fe martensite and B19’-Ti (Ni, Cu) martensite. Ce addition further improved the strengthening and toughening effects of TRIP BMGCs. Adding elemental Ce enhanced the mixing entropy ΔSmix and atomic size difference δ, while reducing the mixing enthalpy ΔHmix, thus improving the glass forming ability and delaying the phase transition process, and hence prolonging the work-hardening period before fracturing. The fracture strength σf and plastic stress εp of Ti39CeNi40Cu20 and Fe64.4CeMn14.3Si9.4Cr10C0.9 alloys were up to 2635 MPa and 13.8%, and 2905 MPa and 30.1%, respectively. Full article
(This article belongs to the Special Issue Advanced High Temperature Shape Memory Alloys)
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Open AccessArticle
Aperiodic Photonics of Elliptic Curves
Crystals 2019, 9(9), 482; https://doi.org/10.3390/cryst9090482 (registering DOI) - 14 Sep 2019
Viewed by 156
Abstract
In this paper we propose a novel approach to aperiodic order in optical science and technology that leverages the intrinsic structural complexity of certain non-polynomial (hard) problems in number theory and cryptography for the engineering of optical media with novel transport and wave [...] Read more.
In this paper we propose a novel approach to aperiodic order in optical science and technology that leverages the intrinsic structural complexity of certain non-polynomial (hard) problems in number theory and cryptography for the engineering of optical media with novel transport and wave localization properties. In particular, we address structure-property relationships in a large number (900) of light scattering systems that physically manifest the distinctive aperiodic order of elliptic curves and the associated discrete logarithm problem over finite fields. Besides defining an extremely rich subject with profound connections to diverse mathematical areas, elliptic curves offer unprecedented opportunities to engineer light scattering phenomena in aperiodic environments beyond the limitations of traditional random media. Our theoretical analysis combines the interdisciplinary methods of point patterns spatial statistics with the rigorous Green’s matrix solution of the multiple wave scattering problem for electric and magnetic dipoles and provides access to the spectral and light scattering properties of novel deterministic aperiodic structures with enhanced light-matter coupling for nanophotonics and metamaterials applications to imaging and spectroscopy. Full article
(This article belongs to the collection Structure and Properties of Quasicrystals)
Open AccessArticle
Space Charge Characteristics and Electrical Properties of Micro-Nano ZnO/LDPE Composites
Crystals 2019, 9(9), 481; https://doi.org/10.3390/cryst9090481 (registering DOI) - 14 Sep 2019
Viewed by 105
Abstract
The synergistic effects of zinc oxide (ZnO) Micro/Nano particles simultaneously filled in low-density polyethylene (LDPE) on the space charge characteristics and electrical properties has been investigated by melt blending micro-scale and nanoscale ZnO additive particles into LDPE matrix to prepare Micro-ZnO, Nano-ZnO, and [...] Read more.
The synergistic effects of zinc oxide (ZnO) Micro/Nano particles simultaneously filled in low-density polyethylene (LDPE) on the space charge characteristics and electrical properties has been investigated by melt blending micro-scale and nanoscale ZnO additive particles into LDPE matrix to prepare Micro-ZnO, Nano-ZnO, and Micro-Nano ZnO/LDPE composites. The morphological structures of composite samples are characterized by Polarizing Light Microscopy (PLM), and the space charge accumulations and insulation performances are correlated in the analyses with Pulse Electronic Acoustic (PEA), DC breakdown field strength, and conductance tests. It is indicated that both the micro and nano ZnO fillers can introduce plenty of heterogeneous nuclei into the LDPE matrix so as to impede the LDPE spherocrystal growth and regularize the crystalline grains in neatly-arranged morphology. By filling microparticles together with nanoparticles of ZnO additives, the space charge accumulations are significantly inhibited under an applied DC voltage and the minimum initial residual charges with the slowest charge decaying rate have been achieved after an electrode short connection. While the micro-nano ZnO/LDPE composites acquire the lowest conductivity, the breakdown strengths of the ZnO/LDPE nanocomposite and micro-nano composite are, respectively, 13.7% and 3.4% higher than that of the neat LDPE material. Full article
(This article belongs to the Special Issue Mesocrystals in Energy Applications)
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Open AccessArticle
Critical Review of Scintillating Crystals for Neutron Detection
Crystals 2019, 9(9), 480; https://doi.org/10.3390/cryst9090480 (registering DOI) - 13 Sep 2019
Viewed by 155
Abstract
There exists an ongoing need to develop and improve methods of detecting radioactive materials. As each radioactive isotope leaves a unique mark in a form of the particles it emits, new materials capable of detecting and measuring these particles are constantly sought. Neutrons [...] Read more.
There exists an ongoing need to develop and improve methods of detecting radioactive materials. As each radioactive isotope leaves a unique mark in a form of the particles it emits, new materials capable of detecting and measuring these particles are constantly sought. Neutrons and their detectors play a significant role in areas such as nuclear power generation, nuclear decommissioning and decontamination, border security, nuclear proliferation and nuclear medicine. Owing to the complexity of their detection, as well as scarcity of 3He, which has historically been the preferred choice for neutron detection in many application fields, new sensitive materials are sought. Organic and inorganic scintillating crystals have been recognised as particularly good alternatives, and as such systems that utilise them are increasingly common. As they allow investigation of the neutron energy spectra, greater information about the radioactive source can be inferred. Therefore, in this article, an extensive review of scintillating crystals used for neutron detection is presented. By describing the history of scintillating crystals and discussing changes that occurred in their use and development of methods for radiation detection, the authors present a comprehensive overview of the current situation. Supported by a practical example, possible future directions of the research area are also presented. Full article
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Open AccessArticle
Application of GISAXS in the Investigation of Three-Dimensional Lattices of Nanostructures
Crystals 2019, 9(9), 479; https://doi.org/10.3390/cryst9090479 (registering DOI) - 13 Sep 2019
Viewed by 135
Abstract
The application of the grazing-incidence small-angle X-ray scattering (GISAXS) technique for the investigation of three-dimensional lattices of nanostructures is demonstrated. A successful analysis of three-dimensionally ordered nanostructures requires applying a suitable model for the description of the nanostructure ordering. Otherwise, it is possible [...] Read more.
The application of the grazing-incidence small-angle X-ray scattering (GISAXS) technique for the investigation of three-dimensional lattices of nanostructures is demonstrated. A successful analysis of three-dimensionally ordered nanostructures requires applying a suitable model for the description of the nanostructure ordering. Otherwise, it is possible to get a good agreement between the experimental and the simulated data, but the parameters obtained by fitting may be completely incorrect. In this paper, we theoretically examine systems having different types of nanostructure ordering, and we show how the choice of the correct model for the description of ordering influences the analysis results. Several theoretical models are compared in order to show how to use GISAXS in the investigation of self-assembled arrays of nanoparticles, and also in arrays of nanostructures obtained by ion-beam treatment of thin films or surfaces. All models are supported by experimental data, and the possibilities and limitations of GISAXS for the determination of material structure are discussed. Full article
(This article belongs to the Special Issue Investigation of Nanostructures with X-ray Scattering Techniques)
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Open AccessReview
Intermolecular Interactions in Functional Crystalline Materials: From Data to Knowledge
Crystals 2019, 9(9), 478; https://doi.org/10.3390/cryst9090478 (registering DOI) - 13 Sep 2019
Viewed by 182
Abstract
Intermolecular interactions of organic, inorganic, and organometallic compounds are the key to many composition–structure and structure–property networks. In this review, some of these relations and the tools developed by the Cambridge Crystallographic Data Center (CCDC) to analyze them and design solid forms with [...] Read more.
Intermolecular interactions of organic, inorganic, and organometallic compounds are the key to many composition–structure and structure–property networks. In this review, some of these relations and the tools developed by the Cambridge Crystallographic Data Center (CCDC) to analyze them and design solid forms with desired properties are described. The potential of studies supported by the Cambridge Structural Database (CSD)-Materials tools for investigation of dynamic processes in crystals, for analysis of biologically active, high energy, optical, (electro)conductive, and other functional crystalline materials, and for the prediction of novel solid forms (polymorphs, co-crystals, solvates) are discussed. Besides, some unusual applications, the potential for further development and limitations of the CCDC software are reported. Full article
(This article belongs to the Special Issue Chemical Bonding in Crystals and Their Properties)
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Open AccessArticle
Two Tetranuclear Butterfly-Shaped Co(II) Complexes: Structure, Mass Spectrometric, and Magnetism
Crystals 2019, 9(9), 477; https://doi.org/10.3390/cryst9090477 (registering DOI) - 13 Sep 2019
Viewed by 112
Abstract
The organic ligand (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (HL) was used to react with CoX2·6H2O (X = Cl and Br) under solvothermal conditions to obtain the complex [Co4(L)6(X)2] (1, X = Cl; 2, [...] Read more.
The organic ligand (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (HL) was used to react with CoX2·6H2O (X = Cl and Br) under solvothermal conditions to obtain the complex [Co4(L)6(X)2] (1, X = Cl; 2, X = Br). The butterfly-shaped structure of complex 1 and 2 suggest that Co(II) ions have two different coordinated modes, which are five coordination with O3NX environment and six coordination with O4N2 environment. In addition, the electrospray ionization mass spectrometry (ESI-MS) analysis indicated that the ion molecular fragment of highest intensity was [Co4(L)6]2+, and there existed a high nuclear fragment peak of [Co7(L)12]2+. Interestingly, it was basically completely transformed into [Co7(L)12]2+ two days later, so those two complexes were relatively stable in CH3OH. Magnetic characterization exhibited that complex 1 and 2 display field-induced single-molecule magnetic behavior, of which the energy hills Ueff/kB were 28 and 20 K under direct-current field of 0.1 T, respectively. Full article
(This article belongs to the Section Crystal Engineering)
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Open AccessArticle
Nanodefects in YAG:Ce-Based Phosphor Microcrystals
Crystals 2019, 9(9), 476; https://doi.org/10.3390/cryst9090476 - 11 Sep 2019
Viewed by 189
Abstract
The present paper focused on the study of spectral–kinetic characteristics of luminescence in two batches of yttrium aluminum garnet (YAG):Ce-based phosphors synthesized in different years by two manufacturers: NPO “Platan” in Russia and “GrandLux” in the People’s Republic of China (PRC). Upon studying [...] Read more.
The present paper focused on the study of spectral–kinetic characteristics of luminescence in two batches of yttrium aluminum garnet (YAG):Ce-based phosphors synthesized in different years by two manufacturers: NPO “Platan” in Russia and “GrandLux” in the People’s Republic of China (PRC). Upon studying the structural characteristics of the phosphors—elemental composition, morphology, and X-ray diffraction (XRD) patterns—it was concluded that both types of YAG:Ce phosphors are highly imperfect. The presence of heterogeneities of different nature was accompanied by the introduction—to compensate for charges and elastic stresses—of intrinsic lattice defects during synthesis. There is a high probability of creating complex defects during phosphor synthesis. Luminescence properties (full width at half maximum (FWHM), spectral position of the emission peaks, excitation spectra of emission, emission decay time) are affected by the nearest environment of the luminescence center; whereas the degree of correlation of defects (distance between the components of the donor–acceptor pair) does not depend on the concentration of impurities, intrinsic defects, and their ratio. The results do not fit into the framework of existing ideas regarding the processes in phosphors as systems with widely distributed luminescence centers. The patterns obtained in the paper are discussed based on a hypothesis according to which a nanodefect phosphorus crystal phase is formed during the synthesis. Full article
(This article belongs to the Special Issue Non-Classical Crystal Growth)
Open AccessFeature PaperReview
Impact of Dispersion of Nanoscale Particles on the Properties of Nematic Liquid Crystals
Crystals 2019, 9(9), 475; https://doi.org/10.3390/cryst9090475 - 11 Sep 2019
Viewed by 179
Abstract
This work reviews the recent progress made in last decade in understanding the role of dispersion of
nanoparticles and quantum dots into host nematic liquid crystals. There are two important ingredients of this work: Even a minute concentration of these non-mesogenic materials in [...] Read more.
This work reviews the recent progress made in last decade in understanding the role of dispersion of
nanoparticles and quantum dots into host nematic liquid crystals. There are two important ingredients of this work: Even a minute concentration of these non-mesogenic materials in host matrix can have reflective impact on the dielectric, electro-optical, and spectroscopic properties of host nematics and the nematic-nanoparticles composite systems become suitable for the use in nematic based display and other devices. Full article
(This article belongs to the Special Issue Liquid Crystal Nanocomposites and Their Photonics Applications)
Open AccessArticle
CuZnSn(SxSe1-x)4 Solar Cell Prepared by the Sol-Gel Method Following a Modified Three-Step Selenization Process
Crystals 2019, 9(9), 474; https://doi.org/10.3390/cryst9090474 - 11 Sep 2019
Viewed by 136
Abstract
In current work, Cu2ZnSn(S,Se)4 thin films have been prepared by the sol-gel method based on dimethyl sulfoxide solution followed by a modified three-step selenization process. The key process of this method is to divide the Se evaporation and annealing into [...] Read more.
In current work, Cu2ZnSn(S,Se)4 thin films have been prepared by the sol-gel method based on dimethyl sulfoxide solution followed by a modified three-step selenization process. The key process of this method is to divide the Se evaporation and annealing into two different stages: employ a thermal cracking Se source in the Se evaporation stage and an above-atmospheric pressure in the annealing process. The morphological, structural, elemental distributional, and photovoltaic properties of Cu2ZnSn(S,Se)4 thin films prepared with the three-step selenization process were systematically investigated. It was found that through this modified selenization process, the formations of secondary phases (ZnSe, CuSnSe3) and a fine-grain bottom layer, which usually exists in the traditional one-step selenization process, were effectively suppressed. These improvements could further reduce the carrier recombination and improve the solar cell performance. The best solar cell is obtained with a short-circuit current density of 28.16 mA/cm2, open-circuit voltage of 404.91 mV, fill factor of 62.91%, and a power conversion efficiency of 7.17% under air mass 1.5 (100 mW/cm2) illumination. Full article
(This article belongs to the Special Issue Advances in Thin Film Solar Cells)
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Open AccessArticle
Dielectric Properties of Chiral Ferroelectric Liquid Crystalline Compounds with Three Aromatic Rings Connected by Ester Groups
Crystals 2019, 9(9), 473; https://doi.org/10.3390/cryst9090473 - 10 Sep 2019
Viewed by 186
Abstract
The tilted ferroelectric SmC* phase of three structurally different series having three aromatic rings in the core structure connected by ester groups with different end alkyl chain lengths, all of which are derived from lactic acid, have been observed by broadband dielectric spectroscopy. [...] Read more.
The tilted ferroelectric SmC* phase of three structurally different series having three aromatic rings in the core structure connected by ester groups with different end alkyl chain lengths, all of which are derived from lactic acid, have been observed by broadband dielectric spectroscopy. Introduction of structural variations within the liquid crystalline compounds has led to the formation of chiral nematic N*, or the paraelectric orthogonal SmA* phase at higher temperatures. The dielectric spectra strongly depend both on the temperature as well as the specific molecular structure of the self-assembling compounds possessing the ferroelectric polar order. The results reveal a strong Goldstone mode in the ferroelectric SmC* phase with ~kHz relaxation frequency. In the SmC* phase, the real and imaginary parts of the complex permittivity increase up to certain temperature near the SmC*-N*/SmA* transition and then decrease with increasing temperature, perhaps due to the disruption of the molecular domains at the onset of the SmA*/N* phase transition. The dielectric strength attains a maximum value in the SmC* phase and then decreases near the SmA*/N* phase transition. The dielectric strength is also influenced by the lengths of the alkyl chain and the nature of the connecting unit of the constituent molecules. The relaxation time and the relaxation frequency are found to vary with the molecular structure of the studied ferroelectric compounds. Full article
(This article belongs to the Special Issue Ferroelectric and Ferromagnetic Liquid Crystals)
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Open AccessArticle
Comparison of Candida Albicans Fatty Acid Amide Hydrolase Structure with Homologous Amidase Signature Family Enzymes
Crystals 2019, 9(9), 472; https://doi.org/10.3390/cryst9090472 - 10 Sep 2019
Viewed by 179
Abstract
Fatty acid amide hydrolase (FAAH) is a well-characterized member of the amidase signature (AS) family of serine hydrolases. The membrane-bound FAAH protein is responsible for the catabolism of neuromodulatory fatty acid amides, including anandamide and oleamide, that regulate a wide range of mammalian [...] Read more.
Fatty acid amide hydrolase (FAAH) is a well-characterized member of the amidase signature (AS) family of serine hydrolases. The membrane-bound FAAH protein is responsible for the catabolism of neuromodulatory fatty acid amides, including anandamide and oleamide, that regulate a wide range of mammalian behaviors, including pain perception, inflammation, sleep, and cognitive/emotional state. To date, limited crystal structures of FAAH and non-mammalian AS family proteins have been determined and used for structure-based inhibitor design. In order to provide broader structural information, the crystal structure of FAAH from the pathogenic fungus Candida albicans was determined at a resolution of 2.2 Å. A structural comparison with a brown rat Rattus norvegicus FAAH as well as with other bacterial AS family members, MAE2 and PAM, showed overall similarities but there were several discriminative regions found: the transmembrane domain and the hydrophobic cap of the brown rat FAAH were completely absent in the fungal FAAH structure. Along with these results, a phylogenetic analysis of 19 species within the AS family showed that fungal FAAHs diverged from a common ancestor before the separation of eukarya and prokarya. Taken together, this study provides insights into developing more potent inhibitors of FAAH as well as expanding our knowledge of the relationships between AS family members. Full article
(This article belongs to the Special Issue Crystallographic Studies of Enzymes)
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Open AccessArticle
Crystal Structure of NADPH-Dependent Methylglyoxal Reductase Gre2 from Candida Albicans
Crystals 2019, 9(9), 471; https://doi.org/10.3390/cryst9090471 - 10 Sep 2019
Viewed by 175
Abstract
Gre2 is a key enzyme in the methylglyoxal detoxification pathway; it uses NADPH or NADH as an electron donor to reduce the cytotoxic methylglyoxal to lactaldehyde. This enzyme is a member of the short-chain dehydrogenase/reductase (SDR) superfamily whose members catalyze this type of [...] Read more.
Gre2 is a key enzyme in the methylglyoxal detoxification pathway; it uses NADPH or NADH as an electron donor to reduce the cytotoxic methylglyoxal to lactaldehyde. This enzyme is a member of the short-chain dehydrogenase/reductase (SDR) superfamily whose members catalyze this type of reaction with a broad range of substrates. To elucidate the structural features, we determined the crystal structures of the NADPH-dependent methylglyoxal reductase Gre2 from Candida albicans (CaGre2) for both the apo-form and NADPH-complexed form at resolutions of 2.8 and 3.02 Å, respectively. The CaGre2 structure is composed of two distinct domains: the N-terminal cofactor-binding domain and the C-terminal substrate-binding domain. Extensive comparison of CaGre2 with its homologous structures reveals conformational changes in α12 and β3′ of the NADPH-complex forms. This study may provide insights into the structural and functional variation of SDR family proteins. Full article
(This article belongs to the Special Issue Crystallographic Studies of Enzymes)
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Open AccessReview
Ferroelectric Liquid Crystals: Physics and Applications
Crystals 2019, 9(9), 470; https://doi.org/10.3390/cryst9090470 - 09 Sep 2019
Viewed by 187
Abstract
Electrooptic modes with fast response and high contrast ratio are highly desirable in modern photonics and displays. Ferroelectric liquid crystals (FLCs) are especially promising for fulfilling these demands by employing photoalignment technology in FLC cells. Three electrooptic modes including surface stabilized FLC (SSFLC), [...] Read more.
Electrooptic modes with fast response and high contrast ratio are highly desirable in modern photonics and displays. Ferroelectric liquid crystals (FLCs) are especially promising for fulfilling these demands by employing photoalignment technology in FLC cells. Three electrooptic modes including surface stabilized FLC (SSFLC), deformed helix ferroelectric (DHF) mode, and electrically suppressed helix (ESH) mode are reviewed with the corresponding electrooptic effects like bi- and multi-stable switching, continuous modulation of grayscale or phase, and high contrast switching. The general operation principles FLC electrooptic modes are described, and then the characteristics of each modes for potential applications are summarized. With the advantages of controllable anchoring energy, the photoalignment provides FLC samples with uniform alignment and high contrast ratio. The fast FLCs with a high resolution and high contrast can be used in the next generation display including field sequential color FLC microdisplays, as well as switchable 2D/3D televisions. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
Open AccessArticle
The Field-Induced Stop-Bands and Lasing Modes in CLC Layers with Deformed Lying Helix
Crystals 2019, 9(9), 469; https://doi.org/10.3390/cryst9090469 - 08 Sep 2019
Viewed by 252
Abstract
Waveguide optical properties of a cholesteric liquid crystal (CLC) layer with a deformed lying helix (DLH) have been studied by numerical simulations using the finite difference time domain method. The DLH structure, when the helix’s axis is oriented in plane of a CLC [...] Read more.
Waveguide optical properties of a cholesteric liquid crystal (CLC) layer with a deformed lying helix (DLH) have been studied by numerical simulations using the finite difference time domain method. The DLH structure, when the helix’s axis is oriented in plane of a CLC layer, is induced by an electric field in a virtual CLC cell with periodic (planar/homeotropic) boundary conditions at one of the alignment surfaces. This in-plane helical structure is stable only in a permanently applied electric field providing the helix deformation. In this work the polarized light reflectance spectra have been studied at different electric fields and light impingement into a waveguide formed by the DLH layer. It is found that for light propagating along the helix axis the reflectance spectrum has multiple stop-bands centred at wavelengths , which is different from set of bands located at , and characteristic of CLC spectra for the Grandjean-plane textures subjected to distortion by an electric or magnetic field perpendicular to the helix axis, where j is a natural number, p is the helix pitch and is the average refractive index. Each of the higher order (j > 1) bands consists of three polarization-dependent sub-bands. In the case of an amplifying CLC DLH layer, depending on an extent of the helix deformation, the lasing modes can be excited at different edges of the sub-bands. While at the strongest deformation the lasing is preferable at the edges of the central sub-band; a lower extent of deformation makes favourable conditions for the lasing at edges of the two other sub-bands. Full article
(This article belongs to the Special Issue Localized Optical Modes in Liquid Crystals)
Open AccessArticle
High Magnetic Field ESR in S = 1 Skew Chain Antiferromagnet Ni2V2O7 Single Crystal
Crystals 2019, 9(9), 468; https://doi.org/10.3390/cryst9090468 - 07 Sep 2019
Viewed by 228
Abstract
We report electron spin resonance (ESR) in S = 1 skew chain antiferromagnet Ni2V2O7, which exhibits a spin-flop transition and a well-defined 1/2 magnetization plateau. The antiferromagnetic (AFM) ordering at TN = 7 K can be [...] Read more.
We report electron spin resonance (ESR) in S = 1 skew chain antiferromagnet Ni2V2O7, which exhibits a spin-flop transition and a well-defined 1/2 magnetization plateau. The antiferromagnetic (AFM) ordering at TN = 7 K can be reflected by the temperature-dependent ESR spectra at low frequency for the easy axis. At 2 K, at the spin-flop transition fields along the easy a and b axes, anomalies are observed from the frequency‒field relationship. However, these modes cannot be understood by the conventional two-sublattice AFM resonance theory with uniaxial anisotropy. For the easy b axis, an unusual resonance mode is observed and its resonance field increases with decreasing frequency. This ESR mode becomes softening at ~8 T, corresponding to the onset of the 1/2 magnetization plateau. Full article
(This article belongs to the Special Issue Magnetic Field-induced Phase Transition)
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Open AccessArticle
Site Selectivity of Halogen Oxygen Bonding in 5- and 6-Haloderivatives of Uracil
Crystals 2019, 9(9), 467; https://doi.org/10.3390/cryst9090467 - 06 Sep 2019
Viewed by 220
Abstract
Seven 5-and 6-halogenated derivatives of uracil or 1-methyluracil (halogen = Cl, Br, I) were studied by single crystal X-ray diffraction. In contrast with pure 5-halouracils, where the presence of N-HO and C-HO hydrogen bonds prevents the formation of other [...] Read more.
Seven 5-and 6-halogenated derivatives of uracil or 1-methyluracil (halogen = Cl, Br, I) were studied by single crystal X-ray diffraction. In contrast with pure 5-halouracils, where the presence of N-HO and C-HO hydrogen bonds prevents the formation of other intermolecular interactions, the general ability of pyrimidine nucleobases to provide electron donating groups to halogen bonding was confirmed in three crystals and cocrystals containing uracil with the halogen atom at the C6 position. In the latter compounds, among the two nucleophilic oxygen atoms in the C=O moiety, only the urea carbonyl oxygen O1 can act as halogen bond acceptor, being not saturated by conventional hydrogen bonds. The halogen bonds in pure 6-halouracils are all rather weak, as supported by Hirshfeld surface analysis. The strongest interaction was found in the structure of 6-iodouracil, which displayed the largest (13%) reduction of the sum of van der Waals (vdW) radii for the contact atoms. Despite this, halogen bonding plays a role in determining the crystal packing of 6-halouracils, acting alongside conventional hydrogen bonds. Full article
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Open AccessArticle
Synthesis and Characterization of a New Aluminum-Doped Bismuth Subcarbonate
Crystals 2019, 9(9), 466; https://doi.org/10.3390/cryst9090466 - 06 Sep 2019
Viewed by 169
Abstract
A new compound, Bi2O2CO3:Al, was synthesized by the coprecipitation method. The characterization was done by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), electronic scanning microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). [...] Read more.
A new compound, Bi2O2CO3:Al, was synthesized by the coprecipitation method. The characterization was done by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), electronic scanning microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The characterization methods allowed to identify the Bi2O2CO3:Al compound, such as the Al-doped Bi2O2CO3 by XRD, the anionic part (CO32−) by FTIR, and the presence of aluminum in the compound by XPS and EDX. It was confirmed to have a nanostructure like a nanosheet and a microstructure that resembles a type sponge by SEM. Full article
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Open AccessArticle
Sensing Characteristics of Side-Polished Fiber Based on the Alterations in Helical Structure of Thermo-Sensitive Cholesteric Liquid Crystals
Crystals 2019, 9(9), 465; https://doi.org/10.3390/cryst9090465 - 05 Sep 2019
Viewed by 171
Abstract
Cholesteric liquid crystals (CLCs) are sensitive to environmental temperature changes, and have been employed as a specific intermediary for biosensors. Considering the temperature-dependent structural changes of CLCs, this study aimed to determine the sensing properties of side-polished fibers (SPFs) after coating with CLCs. [...] Read more.
Cholesteric liquid crystals (CLCs) are sensitive to environmental temperature changes, and have been employed as a specific intermediary for biosensors. Considering the temperature-dependent structural changes of CLCs, this study aimed to determine the sensing properties of side-polished fibers (SPFs) after coating with CLCs. The experimental results demonstrated that, with regard to the transmitted spectrum, the loss peak of CLC-coated SPFs exhibited a positive linear relationship with temperature changes over a range of 20 to 50 °C. The linear correlation coefficient achieved 97.8% when the temperature increased by 10 °C, and the loss peak drifted by 12.72 nm. The reflectance spectrum of CLCs coated on the polished surface were obtained using optical fiber sensors. The feasibility of measuring the helical structure of CLCs was further verified using SPF transmission spectroscopy. The findings indicated that the transmitted spectrum of SPFs could be adopted to characterize the helical structure of CLCs, which lays a solid foundation for further study on SPF-based biosensors. Full article
(This article belongs to the Special Issue Advances in Cholesteric Liquid Crystals)
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Open AccessArticle
Synthesis, Characterization, and Crystal Structure Determination of a New Lithium Zinc Iodate Polymorph LiZn(IO3)3
Crystals 2019, 9(9), 464; https://doi.org/10.3390/cryst9090464 - 04 Sep 2019
Viewed by 237
Abstract
Synthesis and characterization of anhydrous LiZn(IO3)3 powders prepared from an aqueous solution are reported. Morphological and compositional analyses were carried out by using scanning electron microscopy and energy-dispersive X-ray measurements. The synthesized powders exhibited a needle-like morphology after annealing at [...] Read more.
Synthesis and characterization of anhydrous LiZn(IO3)3 powders prepared from an aqueous solution are reported. Morphological and compositional analyses were carried out by using scanning electron microscopy and energy-dispersive X-ray measurements. The synthesized powders exhibited a needle-like morphology after annealing at 400 °C. A crystal structure for the synthesized compound was proposed from powder X-ray diffraction and density-functional theory calculations. Rietveld refinements led to a monoclinic structure, which can be described with space group P21, number 4, and unit-cell parameters a = 21.874(9) Å, b = 5.171(2) Å, c = 5.433(2) Å, and  = 120.93(4)°. Density-functional theory calculations supported the same crystal structure. Infrared spectra were also collected, and the vibrations associated with the different modes were discussed. The non-centrosymmetric space group determined for this new polymorph of LiZn(IO3)3, the characteristics of its infrared absorption spectrum, and the observed second-harmonic generation suggest it is a promising infrared non-linear optical material. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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Open AccessEditorial
First-Principles Prediction of Structures and Properties in Crystals
Crystals 2019, 9(9), 463; https://doi.org/10.3390/cryst9090463 - 04 Sep 2019
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Abstract
The term “first-principles calculations” is a synonym for the numerical determination of the electronic structure of atoms, molecules, clusters, or materials from ‘first principles’, i [...] Full article
(This article belongs to the Special Issue First-Principles Prediction of Structures and Properties in Crystals)
Open AccessFeature PaperArticle
Analysis of Glulisine Crystallisation Utilising Phase Diagrams and Nucleants
Crystals 2019, 9(9), 462; https://doi.org/10.3390/cryst9090462 - 03 Sep 2019
Viewed by 307
Abstract
Glulisine is a US Food and Drug Administration (FDA) approved insulin analogue, used for controlling hyperglycaemia in patients with diabetes mellitus (DM). It is fast acting which better approximates physiological insulin secretion, improving patient outcome. Crystallisation of Glulisine was analysed by its crystallisation [...] Read more.
Glulisine is a US Food and Drug Administration (FDA) approved insulin analogue, used for controlling hyperglycaemia in patients with diabetes mellitus (DM). It is fast acting which better approximates physiological insulin secretion, improving patient outcome. Crystallisation of Glulisine was analysed by its crystallisation phase diagram and nucleation-inducing materials. Both the hanging drop vapour diffusion and microbatch-under-oil methods were used and compared. We have shown that the same protein can have different solubility behaviours depending on the nature of the salt in the precipitating agent. In the case of Glulisine with magnesium formate, lowering the precipitant concentration drove the system further into supersaturation resulting in the formation of crystals and precipitation. This was the opposite effect to the usual scenario where raising the precipitant concentration leads to supersaturation. Glulisine with sodium potassium tartrate tetrahydrate (NaKT) followed the expected trend of forming crystals or precipitate at higher concentrations and clear drops at lower concentrations of the precipitant. The outcomes of crystallisation using the different crystallisation methods is also described. Glulisine was successfully crystallised and the crystals diffracted up to a resolution limit of 1.4 Å. Full article
(This article belongs to the Special Issue Novel Strategies for Improved Protein Crystallization)
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Open AccessArticle
All-Optical Ultra-Fast Graphene-Photonic Crystal Switch
Crystals 2019, 9(9), 461; https://doi.org/10.3390/cryst9090461 - 03 Sep 2019
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Abstract
In this paper, an all-optical photonic crystal-based switch containing a graphene resonant ring has been presented. The structure has been composed of 15 × 15 silicon rods for a fundamental lattice. Then, a resonant ring including 9 thick silicon rods and 24 graphene-SiO [...] Read more.
In this paper, an all-optical photonic crystal-based switch containing a graphene resonant ring has been presented. The structure has been composed of 15 × 15 silicon rods for a fundamental lattice. Then, a resonant ring including 9 thick silicon rods and 24 graphene-SiO2 rods was placed between two waveguides. The thick rods with a radius of 0.41a in the form of a 3 × 3 lattice were placed at the center of the ring. Graphene-SiO2 rods with a radius of 0.2a were assumed around the thick rods. These rods were made of the graphene monolayers which were separated by SiO2 disks. The size of the structure was about 70 µm2 that was more compact than other works. Furthermore, the rise and fall times were obtained by 0.3 ps and 0.4 ps, respectively, which were less than other reports. Besides, the amount of the contrast ratio (the difference between the margin values for logics 1 and 0) for the proposed structure was calculated by about 82%. The correct switching operation, compactness, and ultra-fast response, as well as the high contrast ratio, make the presented switch for optical integrated circuits. Full article
(This article belongs to the Special Issue Sonic and Photonic Crystals)
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Open AccessArticle
Low-Temperature Polymorphic Transformation of β-Lactam Antibiotics
Crystals 2019, 9(9), 460; https://doi.org/10.3390/cryst9090460 - 02 Sep 2019
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Abstract
Abstract: Polymorphic screening and transformation of molecular crystals are presently popular research areas in pharmaceutical studies. In this study, we developed an ab initio method to examine the structures, spectra, and stabilities of β-lactam (trans-13-azabicyclo[10.2.0]tetradecan-14-one), an important component of antibiotics. Based on [...] Read more.
Abstract: Polymorphic screening and transformation of molecular crystals are presently popular research areas in pharmaceutical studies. In this study, we developed an ab initio method to examine the structures, spectra, and stabilities of β-lactam (trans-13-azabicyclo[10.2.0]tetradecan-14-one), an important component of antibiotics. Based on the density functional theory (DFT) and second-order Møller-Plesset perturbation (MP2) methods, the present work demonstrated that forms I and II have isomorphic structures but can be distinguished by their Gibbs free energies and vibrational spectra. Forms I and II show a low-temperature polymorphic transformation at 308 K, where form I is stable below 308 K and form II is stable above 308 K. The proposed method suggests that the theoretical calculation can be used as a tool to effectively distinguish the isomorphic structures, and temperature-induced polymorphic transformation has far-reaching significance for drug storage and design. Full article
(This article belongs to the Special Issue Crystallography of Structural Phase Transformations)
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Open AccessArticle
An Integrated Photonic Electric-Field Sensor Utilizing a 1 × 2 YBB Mach-Zehnder Interferometric Modulator with a Titanium-Diffused Lithium Niobate Waveguide and a Dipole Patch Antenna
Crystals 2019, 9(9), 459; https://doi.org/10.3390/cryst9090459 - 02 Sep 2019
Viewed by 206
Abstract
We studied photonic electric-field sensors using a 1 × 2 YBB-MZI modulator composed of two complementary outputs and a 3 dB directional coupler based on the electro-optic effect and titanium diffused lithium–niobate optical waveguides. The measured DC switching voltage and extinction ratio at [...] Read more.
We studied photonic electric-field sensors using a 1 × 2 YBB-MZI modulator composed of two complementary outputs and a 3 dB directional coupler based on the electro-optic effect and titanium diffused lithium–niobate optical waveguides. The measured DC switching voltage and extinction ratio at the wavelength 1.3 μm were ~16.6 V and ~14.7 dB, respectively. The minimum detectable fields were ~1.12 V/m and ~3.3 V/m, corresponding to the ~22 dB and ~18 dB dynamic ranges of ~10 MHz and 50 MHz, respectively, for an rf power of 20 dBm. The sensor shows an almost linear response to the applied electric-field strength within the range of 0.29 V/m to 29.8 V/m. Full article
(This article belongs to the Special Issue Recent Progress in Lithium Niobate)
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Open AccessArticle
Autowave Physics of Material Plasticity
Crystals 2019, 9(9), 458; https://doi.org/10.3390/cryst9090458 - 02 Sep 2019
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Abstract
The notions of plastic flow localization are outlined in the paper. It is shown that each type of localized plasticity pattern corresponds to a definite stage of deformation hardening. In the course of plastic flow development, a changeover in the types of localization [...] Read more.
The notions of plastic flow localization are outlined in the paper. It is shown that each type of localized plasticity pattern corresponds to a definite stage of deformation hardening. In the course of plastic flow development, a changeover in the types of localization patterns occurs. The types of localization patterns are limited in number: four pattern types are all that can be expected. A correspondence was set up between the emergent localization pattern and the respective flow stage. It is found that the localization patterns are manifestations of the autowave nature of plastic flow localization process, with each pattern type corresponding to a definite mode of autowave. In the course of plastic flow development, the following modes of autowaves will form in the following sequence: switching autowave → phase autowave → stationary dissipative structure → collapse of the autowave. Of particular interest are the phase autowave and the respective pattern observed. Propagation velocity, dispersion, and grain size dependence of wavelength were determined experimentally for the phase autowave. An elastic-plastic strain invariant was also introduced to relate the elastic and plastic properties of the deforming medium. It is found that the autowave characteristics follow directly from this invariant. Full article
(This article belongs to the Special Issue Elasticity and Micro- and Macro- Plasticity of Crystals)
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Open AccessArticle
Bubbly Water as a Natural Metamaterial of Negative Bulk-Modulus
Crystals 2019, 9(9), 457; https://doi.org/10.3390/cryst9090457 - 01 Sep 2019
Viewed by 539
Abstract
In this study, an oscillator model of bubble-in-water is proposed to analyze the effective modulus of low-concentration bubbly water. We show that in a wide range of wave frequency the bubbly water acquires a negative effective modulus, while the effective density of the [...] Read more.
In this study, an oscillator model of bubble-in-water is proposed to analyze the effective modulus of low-concentration bubbly water. We show that in a wide range of wave frequency the bubbly water acquires a negative effective modulus, while the effective density of the medium is still positive. These two properties imply the existence of a wide acoustic gap in which the propagation of acoustic waves in this medium is prohibited. The dispersion relation for the acoustic modes in this medium follows Lorentz type dispersion, which is of the same form as that of the phonon-polariton in an ionic crystal. Numerical results of the gap edge frequencies and the dispersion relation in the long-wavelength regime based on this effective theory are consistent with the sonic band results calculated with the plane-wave expansion method (PWEM). Our theory provides a simple mechanism for explaining the long-wavelength behavior of the bubbly water medium. Therefore, phenomena such as the high attenuation rate of sound or acoustic Anderson localization in bubbly water can be understood more intuitively. The effects of damping are also briefly discussed. This effective modulus theory may be generalized and applied to other bubble-in-soft-medium type sonic systems. Full article
(This article belongs to the Special Issue Sonic and Photonic Crystals)
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Open AccessArticle
Development of a Stainless Austenitic Nitrogen-Alloyed CrMnNiMo Spring Steel
Crystals 2019, 9(9), 456; https://doi.org/10.3390/cryst9090456 - 31 Aug 2019
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Abstract
The generation of a nickel-reduced, stainless spring steel strip with a thickness of 0.2 mm, producible under industrial conditions, is the aim of a transfer project together with the Institute of Metal Forming/TU BAF and the Auerhammer Metallwerk GmbH within the DFG Collaborative [...] Read more.
The generation of a nickel-reduced, stainless spring steel strip with a thickness of 0.2 mm, producible under industrial conditions, is the aim of a transfer project together with the Institute of Metal Forming/TU BAF and the Auerhammer Metallwerk GmbH within the DFG Collaborative Research Centre (CRC) 799. The spring steel strip should exhibit a tensile strength of ≥1700 MPa in work-hardened and partitioned state. The mechanical and corrosive properties of the steel strip should be equal or better than those given for 1.4310 steel (AISI 301). The article presents the results of laboratory alloys focused on the design of steel strips, which meet the requirements for a cost-effective production. The results presented relate to steel design, microstructure formation, temperature-dependent mechanical properties, and corrosion resistance. Four alloys of the type X5CrMnNiMoN16-x-4 with manganese contents of approximately 2 to 6 wt.-percent were investigated. The austenitic steel X5CrMnNiMoN16-4-4 with TRIP/TWIP effect was selected for deformation and partitioning treatments. Its deformation-induced α’-martensite formation significantly contributes to the work hardening of the steel. A short-time annealing treatment (partitioning) further increases the strength properties. Full article
(This article belongs to the Special Issue Mechanical Behaviour of Austenitic Stainless Steels)
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Open AccessReview
Lyotropic Liquid Crystals from Colloidal Suspensions of Graphene Oxide
Crystals 2019, 9(9), 455; https://doi.org/10.3390/cryst9090455 - 31 Aug 2019
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Abstract
Lyotropic liquid crystals from colloidal particles have been known for more than a century, but have attracted a revived interest over the last few years. This is due to the developments in nanoscience and nanotechnology, where the liquid crystal order can be exploited [...] Read more.
Lyotropic liquid crystals from colloidal particles have been known for more than a century, but have attracted a revived interest over the last few years. This is due to the developments in nanoscience and nanotechnology, where the liquid crystal order can be exploited to orient and reorient the anisotropic colloids, thus enabling, increasing and switching the preferential properties of the nanoparticles. In particular, carbon-based colloids like carbon nanotubes and graphene/graphene–oxide have increasingly been studied with respect to their lyotropic liquid crystalline properties over the recent years. We critically review aspects of lyotropic graphene oxide liquid crystal with respect to properties and behavior which seem to be generally established, but also discuss those effects that are largely unfamiliar so far, or as of yet of controversial experimental or theoretical outcome. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessEditorial
Metal Phosphonates and Phosphinates
Crystals 2019, 9(9), 454; https://doi.org/10.3390/cryst9090454 - 31 Aug 2019
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Abstract
The present Special Issue entitled “Metal phosphonates and phosphinates” aims to collect recent and significant research papers on the fascinating chemistry of these two related families of coordination compounds [...] Full article
(This article belongs to the Special Issue Metal Phosphonates and Phosphinates)
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