Properties Of Crystals Research Articles

Molecular Structures, Dipole Moments, and Electronic Properties of β-HMX under External Electric Field from First-Principles Calculations.

In order to investigate the impact of an external electric field on the sensitivity of β-HMX explosives, we employ first-principles calculations to determine the molecular structure, dipole moment, and electronic properties of both β-HMX crystals and individual β-HMX molecules under varying electric fields. When the external electric field is increasing along the [100], [010], and [001] crystallographic directions of β-HMX, the calculation results indicate that an increase in the bond length (N1-N3/N1'-N3') of the triggering bond, an increase in the main Qnitro (N3, N3') value, an increase in the minimum surface electrostatic potential, and a decrease in band gap all contribute to a reduction in its stability. Among these directions, the [010] direction exhibits the highest sensitivity, which can be attributed to the significantly smaller effective mass along the [010] direction compared with the [001] and [100] directions. Moreover, the application of an external electric field along the Y direction of the coordinate system on individual β-HMX molecules reveals that the strong polarization effect induced by the electric field enhances the decomposition of the N1-N3 bonds. In addition, due to the periodic potential energy of β-HXM crystal, the polarization effect of β-HMX crystal caused by an external electric field is much smaller than that of a single β-HXM molecule.

Effect of Gadolinium Addition on Magnetic and Magneto-Optical Properties of Yttrium Iron Garnet Crystal

Effect of Gadolinium Addition on Magnetic and Magneto-Optical Properties of Yttrium Iron Garnet Crystal

Phase Transitions and Nonlinear Optical Property Modifications in BaGa4Se7.

Phase transitions can change the crystal structure and modify the physical properties of crystals. In this work, we investigate the phase transition behavior in BaGa4Se7, an important middle infrared (mid-IR) nonlinear optical (NLO) crystal, in the temperature range from room temperature to 1173 K. Interestingly, the BaGa4Se7 crystal undergoes a reversible ferroelastic phase transition at T = 528 K, resulting in the presence of a newly discovered phase (γ-phase) at the higher temperature. The experimental temperature dependence of optical birefringence, as well as the first-principles birefringence and NLO coefficients, reveals that the γ-phase exhibits larger birefringence and better NLO properties compared with those of the low-temperature phase (α-phase). This work demonstrates that phase-transition-induced structural modification can improve the mid-IR NLO properties, which would provide an effective avenue to obtain materials with good optoelectronic performance.

Study of high temperature mechanical properties and damage behavior of Ni-YSZ anode/SrO–MgO–SiO2 glass-ceramic sealant/430 s.s. interconnect system in solid oxide fuel cells (SOFC)

In the sealing system of Ni-YSZ anode/SrO–MgO–SiO2 glass-ceramic sealant/430 s s. interconnect, the phase transformation and mechanical properties of interfaces are studied after operating 0 h, 100 h, and 1800 h at 750 °C. The results show that the interface fracture appears in the glass/anode and glass/interconnect interfaces after operating at 1800 h. The interface mechanical parameters within different operation times are collected to investigate the effects of crystallization, penetration, and high temperature mechanical properties on the interlayer stress and structure damage. The Sr2MgSi2O7 crystal phase increases the glass modulus from 104.5 GPa to 129.8 GPa with a runtime from 0 h to 1800 h. The modulus of the Ni-YSZ interface also increases from 82.4 GPa to 128.3 GPa with the glass penetration process. The 430 s s. modulus is reduced by 13 % at 750 °C after 1800 h to reach 191.1 GPa. The established anode/glass/interconnect interlayer stress model accurately calculates the compressive stress at the glass/anode side interface and glass/interconnect side interface, with values reaching −755.2 MPa and −587.1 MPa, respectively. The crystallization zone of the SrO–MgO–SiO2 glass-side interface near Ni-YSZ and 430 s s. become the stress damage sensitive zones and break under interlayer stress.

DFT studies on electronic and structure properties of PbSe1-xSx alloys for thermoelectric materials using VCA and RS

In this work, Density Functional Theory (DFT) was employed to investigate the crystal structure and electronic properties of lead selenide (PbSe) and lead sulfide (PbS) semiconductors and their pseudo binary alloys PbSe1-xSx. The virtual crystal approximation (VCA) and randomly substituted solid models were employed to study these materials. In addition, the thermoelectric properties as function of the alloy composition were studied. Lattice parameters obtained using the generalized gradient approximation (GGA) were compared with theoretical and experimental results. The electronic bands were calculated for different sulfur compositions (0≤x ≤ 1, Δx = 0.1) using the Generalized Gradient Approximation of TB09LDA (MGGA). It was observed that the transition from the valence band to the conduction band takes place at the L point, which agrees with previous theoretical investigations. Slight deviations from Vegard's law were observed in the lattice parameters and bandgap of the alloys, especially for the sulfur-rich alloys. Effective band diagrams obtained from the unfolding of supercell band diagrams, reported for the first time for this system, show that the impacts of alloy disorder are low in the vicinity of the L point. The influence of the alloy composition on the transport properties was studied within the framework of Boltzmann's semiclassical theory. The electrical conductivity shows a thermally activated increase which influences the total thermal conductivity above T > 600–700 K, and the figure of merit ZT. Seebeck coefficient dependence with the chemical potential suggests an ambipolar behavior of the alloys, which present both n and p character. The alloys have the ZT maxima above 900 K influenced by the PbSe1-xSx alloy composition. Remarkably, the alloy with x = 0.5 present a maximum ZT value comparable to that of PbSe, which indicates that is promising to substituting selenium by sulfur atoms to tailor the thermoelectrical properties. This work shows the suitability of the VCA approximation and the band unfolding method, to describe the composition-dependent properties of the PbSe1-xSx pseudo binary alloys.

Synthesis, Crystal Structure, and Optical and Magnetic Properties of the New Quaternary Erbium Telluride EuErCuTe3: Experiment and Calculation

This paper reports for the first time on a new layered magnetic heterometallic erbium telluride EuErCuTe3. Single crystals of the compound were obtained from the elements at 1120 K using CsI as a flux. The crystal structure of EuErCuTe3 was solved in the space group Cmcm (a = 4.3086(3) Å, b = 14.3093(9) Å, and c = 11.1957(7) Å) with the KZrCuS3 structure type. In the orthorhombic structure of erbium telluride, distorted octahedra ([ErTe6]9−) form two-dimensional layers (Er(Te1)2/2e(Te2)4/2k−∞2), while distorted tetrahedra ([CuTe4]7−) form one-dimensionally connected substructures (Cu(Te1)2/2e(Te2)2/1t5−∞1) along the [100] direction. The distorted octahedra and tetrahedra form parallel two-dimensional layers (CuErTe32−∞2) between which Eu2+ ions are located in a trigonal-prismatic coordination environment (EuTe610−). The trigonal prisms are connected by faces, forming chains (Eu(Te1)2/2(Te2)4/22−∞1) along the [100] direction. Regularities in the variations in structural parameters were established in the series of erbium chalcogenides (EuErCuCh3 (Ch = S, Se, and Te)) and tellurides (EuLnCuTe3 (Ln = Gd, Er, and Lu)). Ab-initio calculations of the crystal structure, phonon spectrum, and elastic properties of the compound EuErCuTe3 were performed. The types and wavenumbers of fundamental modes were determined, and the involvement of ions in the IR and Raman modes was assessed. The experimental Raman spectra were interpreted. The telluride EuErCuTe3 at temperatures below 4.2 K was ferrimagnetic, as were the sulfide and selenide derivatives (EuErCuCh3 (Ch = S and Se)). Its experimental magnetic characteristics were close to the calculated ones. The decrease in the magnetic phase transition temperature in the series of the erbium chalcogenides was discovered.

Photo-Responsive Hydrogen-Bonded Molecular Networks Capable of Retaining Crystalline Periodicity after Isomerization.

The molecular conformation, crystalline morphology, and properties of photochromic organic crystals can be controlled through photoirradiation, making them promising candidates for functional organic materials. However, photochromic porous molecular crystals with a networked framework structure are rare due to the difficulty in maintaining space that allows for photo-induced molecular motion in the crystalline state. This study describes a photo-responsive single crystal based on hydrogen-bonded (H-bonded) network of dihydrodimethylbenzo[e]pyrene derivative 4BDHP. A crystal composed of H-bonded undulate layers, 4BDHP-2, underwent photo-isomerization in the crystalline state due to loose stacking of the layers. Particularly, enantio-pure crystal (S,S)-4BDHP-2 allowed to reveal the structure of the photoisomerized crystal, in which the closed form (4BDHP) and open form (4CPD) were arranged alternately with keeping crystalline periodicity, although side reactions were also implied. The present proof-of-concept system of a photochromic framework that retains crystalline periodicity after photo-isomerization may provide new light-driven porous functional materials.

Photo‐Responsive Hydrogen‐Bonded Molecular Networks Capable of Retaining Crystalline Periodicity after Isomerization

AbstractThe molecular conformation, crystalline morphology, and properties of photochromic organic crystals can be controlled through photoirradiation, making them promising candidates for functional organic materials. However, photochromic porous molecular crystals with a networked framework structure are rare due to the difficulty in maintaining space that allows for photo‐induced molecular motion in the crystalline state. This study describes a photo‐responsive single crystal based on hydrogen‐bonded (H‐bonded) network of dihydrodimethylbenzo[e]pyrene derivative 4BDHP. A crystal composed of H‐bonded undulate layers, 4BDHP‐2, underwent photo‐isomerization in the crystalline state due to loose stacking of the layers. Particularly, enantio‐pure crystal (S,S)‐4BDHP‐2 allowed to reveal the structure of the photoisomerized crystal, in which the closed form (4BDHP) and open form (4CPD) were arranged alternately with keeping crystalline periodicity, although side reactions were also implied. The present proof‐of‐concept system of a photochromic framework that retains crystalline periodicity after photo‐isomerization may provide new light‐driven porous functional materials.

Enhanced long-term performance of ureteral stents with functional coating: Combating bacterial adhesion and inhibiting encrustation

Long-term indwelling ureteral stents in urology surgeries often lead to severe encrustation and challenging clinical complications, necessitating an effective medical response. Although many researchers have started with antibacterial, anti-fouling and other aspects, the lack of direct urinary pertinence or develop drug resistance have not really improved the current situation of crust. Therefore, while giving full play to the excellent properties of coated anti-bacterial adhesion, it is still a challenging problem to ensure that it can be effectively applied to ureteral stents and urinary tract environment. Herein, this work proposes a practical functional coating to inhibit encrustation, achieved by incorporating the urinary crystal inhibitor citric acid to crosslink the polyvinylpyrrolidone with hydrophilic lubrication properties (PVP/CA). The coating based on charge interaction has excellent stability (peel strength up to 600 N/m) excellent wettability (contact angle reduced by 60°), lubricity (friction coefficient reduced by 4 times) and biocompatibility. More importantly, the synergistic anti-bacteria adhesion (>90 %) and inhibition of urinary tract crystallization properties of the coated ureteral stent demonstrate superior performance in preventing encrustation over a 4-week period in an in vitro model. This innovative coating strategy holds promising prospects for ureteral stents, offering a potential solution to alleviate pain in urological patients.

Crystallization of KDP in the presence of 4-nitro benzoic acid, L-ornithine hydrochloride and terephthalic acid

The present study is to investigate the optical, thermal and SHG properties of grown potassium dihydrogen phosphate (KDP) crystals using slow evaporation method in the presence of 4-nitro benzoic acid, l-Ornithine Hydrochloride and Terephthalic acid. Powder crystal XRD studies confirm their structure as that of KDP. The presence of functional groups has been tested and confirmed by FTIR. UV–visible spectral analysis - Differential Reflectance Studies (DRS) is used to examine the optical properties of pure and doped KDP crystals within the wavelength range of 200–800 nm and also evaluate the band gap, refractive index, extinction coefficient and optical conductivity of the grown crystals. Thermal properties of grown crystal are analysed by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Second harmonic generation test is carried out for the grown crystals to analyse nonlinear optical (NLO) properties.

Structural, magnetic, and electronic properties of a GdAsSe single crystal: Experimental and theoretical studies

Structural, magnetic, and electronic properties of a GdAsSe single crystal: Experimental and theoretical studies

The impact of bi-doped on MAPb(IxBr1–x)3 mixed halide perovskite films

Perovskite solar cells have attracted considerable attention from researchers owing to their cost-effective manufacturing processes, facilitating their suitability for commercialization. Halide perovskite such as methylammonium lead iodide (MAPbI3), methylammonium lead bromide (MAPbBr3) and other mixed halide perovskite are intensively studied as light absorber for solar cells. In order to adjust the properties of the perovskite, doping with heterovalent metal ions such as bismuth iodide, BiI3, has demonstrated notable impact on both crystal structure and optical properties. Traditionally, Bi3+ doping has been conducted primarily in single halide perovskite. However, our study explored the possibility of Bi3+ doping at a concentrations of 5% in mixed halide perovskite, specifically the mixed iodide-bromide perovskite, MAPb(IxBr1–x)3 at x = 0.2, 0.4, 0.6 and 0.8. The XRD results revealed a decrease in lattice constant upon Bi3+ doping which likely attributed to the smaller ionic radius of Bi3+ compared to Pb2+. The light absorption spectra of Bi3+ doping perovskites exhibited a significant red shift compared to the undoped samples. The presences of the key elements are confirmed by photoemission spectroscopy results. Moreover, our investigation found no notable effect on the valence band maximum upon doping. The observed red-shift presents a potential advantage for precisely adjusting the absorption edge in tandem solar cells, particularly when specific energy gaps are required.

Biphenyls embedded Schiff base-bis esters: self-assembling behaviour, impact of additional aromatic ring and ester linkage and their DFT investigations

ABSTRACT In the present investigation, two series of biphenyl embedded Schiff base-bis esters alkyl-(E)-4-(((4’-(decyloxy)-[1,1’-biphenyl]-4-yl)methylene)amino)-benzoate, BPK-(2–18) and alkyl-(E)-4-(((4’-((4-(decyloxy)benzoyl)oxy)-[1,1’-biphenyl]-4-yl)-methylene)amino)benzoate, BPEK-(8–18) containing either terminal alkoxy biphenyl core or central biphenyl core have been synthesised and studied for their self-assembling behaviour. The compounds of both series demonstrated enantiotropic liquid crystal properties, displaying typical calamitic mesophases (Smectic A (SmA), Smectic C (SmC)) across a broad temperature range and with high thermal stability. The bimorphic behaviour of new molecules has been investigated by VT-XRD analysis. The density function theory has been done to illustrate the experimental results of the mesomorphic properties of the studied compounds. Several parameters have been calculated such as molecular geometry, dipole moment, polarisability, aspect ratio, etc. The results showed that more planar compounds will attain more packed structures leading to the formation of more ordered smectic phases.

Regular relations of the composition, structure and properties of crystals of hydrogen-containing compounds

Research subject. Crystals of hydrogen-containing compounds belonging to the superprotonic family. Aim. To obtain knowledge about regular relations between composition, atomic structure, real structure and physical properties of materials, with the purpose of elucidating processes occurring in condensed state and forming the basis for modification of known or obtaining new compounds. Materials and methods. Experimental data were obtained using a set of complementary physical methods, including structural analysis using X-rays, synchrotron radiation and neutrons, optical microscopy, and atomic force microscopy. Results. Experimental data on the atomic structure, real structure, and physical properties of superprotonic crystals, including systems of hydrogen bonds and their changes, were obtained. Conclusions. The physical properties of superprotonic crystals are significantly affected by hydrogen bonding systems and their changes, primarily by the formation of dynamically disordered hydrogen bonds with energetically equivalent positions of hydrogen atoms. When carrying out diagnostics of crystalline samples, account should be taken of their real structure, including the structure of surface layers and the presence of crystallization water. These factors may affect the measured physical parameters, the boundaries of existence of phases, the formation of a multiphase state under variations in temperature.

Strategies to Diversification of the Mechanical Properties of Organic Crystals

AbstractStructurally ordered soft materials that respond to complementary stimuli are susceptible to control over their spatial and temporal morphostructural configurations by intersectional or combined effects such as gating, feedback, shape‐memory, or programming. In the absence of general and robust design and prediction strategies for their mechanical properties, at present, combined chemical and crystal engineering approaches could provide useful guidelines to identify effectors that determine both the magnitude and time of their response. Here, we capitalize on the purported ability of soft intermolecular interactions to instigate mechanical compliance by using halogenation to elicit both mechanical and photochemical activity of organic crystals. Starting from (E)‐1,4‐diphenylbut‐2‐ene‐1,4‐dione, whose crystals are brittle and photoinert, we use double and quadruple halogenation to introduce halogen‐bonded planes that become interfaces for molecular gliding, rendering the material mechanically and photochemically plastic. Fluorination diversifies the mechanical effects further, and crystals of the tetrafluoro derivative are not only elastic but also motile, displaying the rare photosalient effect.

Strategies to Diversification of the Mechanical Properties of Organic Crystals.

Structurally ordered soft materials that respond to complementary stimuli are susceptible to control over their spatial and temporal morphostructural configurations by intersectional or combined effects such as gating, feedback, shape-memory, or programming. In the absence of general and robust design and prediction strategies for their mechanical properties, at present, combined chemical and crystal engineering approaches could provide useful guidelines to identify effectors that determine both the magnitude and time of their response. Here, we capitalize on the purported ability of soft intermolecular interactions to instigate mechanical compliance by using halogenation to elicit both mechanical and photochemical activity of organic crystals. Starting from (E)-1,4-diphenylbut-2-ene-1,4-dione, whose crystals are brittle and photoinert, we use double and quadruple halogenation to introduce halogen-bonded planes that become interfaces for molecular gliding, rendering the material mechanically and photochemically plastic. Fluorination diversifies the mechanical effects further, and crystals of the tetrafluoro derivative are not only elastic but also motile, displaying the rare photosalient effect.

Tailoring surface defects to enhance PBX surface adhesion through autologous surface molecular reconfiguration

Surface modification of explosive crystals is crucial for enhancing the performance of explosives, particularly polymer-bonded explosives (PBXs). Traditional methods to boost mechanical properties in PBXs, such as surface coating, often encounter issues like complex operations, inadequate adhesion, and impurity introduction. In this paper, direct surface modification via the assembly-disassembly of NH…O hydrogen bond synthon was presented for enhancing interfacial adhesion. Using the autologous surface molecular reconfiguration resulting from hydrogen bond synthon, diverse surface defects were introduced on crystals. The notable surface alterations are influenced by concentration and suspension time. The crystal surface with irregular surface morphology adheres more strongly to the binders and its PBXs were increased the elastic recovery by 28.9 % compared to the raw material. Furthermore, this technique of altering crystal surface properties by introducing surface defects not only maintains the purity of the particles but simplifies the preparation process, making it efficient and environmentally friendly.

Enhanced Magnetoimpedance Effect in Co-Based Micron Composite CoFeNiSiB Ribbon Strips Coated by Carbon and FeCoGa Nanofilms for Sensing Applications

Quenched Co-based ribbon strips are widely used in the fields of magnetic amplifier, magnetic head material, magnetic shield, electric reactor, inductance core, sensor core, anti-theft system label, and so on. In this study, Co-based composite CoFeNiSiB ribbon strips with a micron width were fabricated by micro-electro-mechanical systems (MEMS) technology. The carbon and FeCoGa nanofilms were deposited for surface modification. The effect of carbon and FeCoGa nanofilm coatings on the crystal structure, surface morphology, magnetic properties, and magnetoimpedance (MI) effect of composite ribbon strips were systematically investigated. The results show that the surface roughness and coercivity of the composite ribbon strips are minimum at a thickness of the carbon coating of 60 nm. The maximum value of MI effect is 41% at 2 MHz, which is approximately 2.4 times greater than plain ribbon and 1.6 times greater than FeCoGa-coated composite ribbon strip. The addition of a carbon layer provides a conductive path for high frequency currents, which effectively reduces the characteristic frequency of the composite ribbon strip. The FeCoGa coating is able to close the flux path and reduce the coercivity, which, in turn, increases the transverse permeability and improves the MI effect. The findings indicate that a successful combination of carbon layer and magnetostrictive FeCoGa nanofilm layer can improve the MI effect and magnetic field sensitivity of the ribbon strips, demonstrating the potential of the composite strips for local and micro area field sensing applications.

Thermal ratcheting of uranium simulated with a thermo-elasto-visco-plastic self-consistent polycrystal model

Uranium polycrystal aggregates accumulate large plastic deformation during thermal cycling in a process known as thermal ratcheting. This process is induced by highly anisotropic single crystal properties, texture, and a complex coupling between thermal, elastic, and plastic mechanisms of deformation. In this study, a thermo-elasto-visco-plastic polycrystal model is developed and applied to the prediction of thermal ratcheting in uranium. The model is based on the evolution of dislocation density on individual slip systems and accounts for static recovery effects. The model captures the plastic relaxation of intergranular stresses induced by thermal cycling and leads to quantitative understanding of the coupling between thermal, elastic and plastic mechanisms, and the important role played by static dislocation recovery in uranium. Results are compared with thermal ratcheting measurements.

Hot deformation, processing maps, and microstructural evolution of Ti/Ni/Ti layered composites

Ti/Ni/Ti layered composites, which combine the advantages of Ti and Ni, are widely used in sensor and biomedical applications due to their light weight, high strength, high conductivity, good stability and excellent corrosion resistance. However, it is difficult to control the structural parameters, microstructure, and mechanical properties of layered composites during co-deformation processing due to the distinct differences in the crystal structure, mechanical properties, and deformation behavior of Ti and Ni layers. In this paper, the hot deformation, processing maps, and microstructural evolution of Ti/Ni/Ti layered composites during hot deformation processing are investigated through hot compression tests at 550–850 °C/0.001–1.0 s−1, with a reduction of 65%. It is shown that the composites exhibit mainly dynamic recovery or similar dynamic recrystallization characteristics. Combined with the interface structure, processing maps and microstructure, the optimal parameters for Ti/Ni/Ti layered composites are 680–730 °C/0.007–0.015 s−1. During co-deformation, the microstructural evolution of the constituent layers is very complex. The deformation mechanism is mainly dynamic recovery (DRV), or DRV and dynamic recrystallization (DRX) in Ti layer, and work hardening (WH) or DRV in Ni layer.