Lattice Parameters Research Articles

Crystal Growth and Structural Analysis of Layered Lithium Titanium Sulfide.

Layered sulfide crystals are suitable hosts for lithium and sodium ions in batteries. In this study, new layered lithium titanium sulfide (LTS) crystals were grown in a sealed silica tube using a Li2S self-flux at 800-950 °C. X-ray diffraction (XRD) analysis results indicated the formation of a new sulfide phase with higher symmetry in the Li-Ti-S system. The chemical compositions of the resulting crystals were estimated to be Li1.8TiS2.7 from elemental analysis, and indexing the XRD pattern of LTS afforded lattice constants and the monoclinic space group C2/m (no. 12). Based on these results, an initial structural model of LTS was constructed and verified using Rietveld refinement. The characterization results indicated that the grown LTS crystals had a layered structure with lithium and silicon deficiencies in Li2TiS3. The use of Li2S self-flux at 950 °C enabled the effective growth of LTS crystals with sizes of 10-20 μm. Electrochemical measurements confirmed the Li+ insertion-extraction characteristics of the LTS crystals.

Lattice coherency engineering trigger rapid charge transport at the heterointerface of Te/In2O3@MXene photocatalysts for boosting photocatalytic hydrogen evolution.

The establishment of heterojunctions has been demonstrated as an effective method to improve the efficiency of photocatalytic hydrogen production. Conventional heterojunctions usually have random orientation relationships, and heterointerfaces can hinder photogenerated carrier transport due to larger lattice mismatches, thus reducing the photoelectric conversion efficiency. In this study, a novel Te/In2O3@MXene lattice coherency heterojunction was prepared by leveraging the identical lattice spacing of In2O3 (222) and Te (021) crystal face. The lattice consistency facilitates enhanced photogenerated carrier transport rate between the heterostructure interface of In2O3 and Te. Furthermore, the incorporation of MXene, the electrons originating from Te 5p orbital achieve directional transfer in the heterojunction. This reduces the recombination of photogenerated electron - hole pairs and retains the photogenerated electrons with higher reducibility. The hydrogen production efficiency of Te/In2O3@MXene is 568.8μmol/h g-1, which is 24 times higher than that of pristine In2O3, and it remains 90% of its initial activity after six cycles. This study offers a novel approach to address the escalating carrier transfer resistance commonly observed in conventional heterojunctions.

Wearless-nanofrictional law regarding sliding-speed thresholds elucidated by elaborate nonequilibrium molecular dynamics study

ABSTRACT This investigation explored universal features of sustained dynamic friction between atomically flat surfaces (hereinafter referred to simply as ‘nanofriction’). The sliding-speed dependence of the wearless-nanofrictional force density is predicted to be characterised by the threshold phenomenon originating from the spatial translational symmetry of the interfacial atomic configuration along the sliding direction. Molecular dynamics (MD) simulations were performed for steady wearless nanofriction between nonmetallic crystals. In the present study, accurate ensemble-averaged data on the sliding-speed dependence were obtained comprehensively for various lattice-constant pairs (i.e. combinations of the lattice constants of the two crystals along the sliding direction) and interfacial temperatures. Analyses of these accurate results revealed an unambiguous, simple relationship holding between the sliding-speed threshold and the lattice-constant pair. This article organises the fundamental aspects of the threshold phenomenon and the phononic energy-dissipation mechanisms underlying these aspects to conclude the MD investigation concerning nanofriction between two basic-structure lattices. Understanding the universal features of the accurate sliding-speed dependence is expected to aid in developing artificial materials for the sliding parts of nanoelectromechanical systems (NEMSs).

Electrical Control of Photoluminescence in 2D Semiconductors Coupled to Plasmonic Lattices.

Integrating two-dimensional (2D) semiconductors into nanophotonic structures provides a versatile platform for advanced optoelectronic devices. A key challenge in realizing these systems is to achieve control over light emission from these materials. In this work, we demonstrate the modulation of photoluminescence (PL) in transition metal dichalcogenides (TMDs) coupled to surface lattice resonances in metal nanoparticle arrays. We show that both the intensity and the emission angle of light can be tuned by adjusting the lattice parameters. By applying gate electrodes to electrostatically dope the TMDs coupled to plasmonic lattices, we achieve PL intensity switching over 2 orders of magnitude with a low applied voltage. Our results represent an important step toward electrically powered and electrically tunable light sources based on 2D semiconductors.

Microwave-Assisted Green Synthesis of Fluorescent Graphene Quantum Dots: Metal Sensing, Antioxidant Properties, and Biocompatibility Insights.

Graphene quantum dots (GQDs) are highly valued for their chemical stability, tunable size, and biocompatibility. Utilizing green chemistry, a microwave-assisted synthesis method was employed to produce water-soluble GQDs from Mangifera Indica leaf extract. This approach is efficient, cost-effective, and environmentally friendly, offering reduced reaction times, energy consumption, and uniform particle sizes, and has proven advantageous over other methods. Water-soluble GQDs were synthesized using Mangifera Indica leaf extract, which ranged less than 15nm in diameter, confirmed by high-resolution transmission electron microscopy with a lattice spacing of 0.34nm. The GQDs exhibited strong photoluminescence with bright red fluorescence under UV light and excitation-independent emission at 662nm with excitation wavelengths ranging from 300 to 500nm, achieving a quantum yield of 10.3%. A peak at 27.2˚ was recorded corresponding to the graphite's (002) plane diffraction peak. Raman spectroscopy confirmed their graphitic nature and sp2 crystallinity, with an intensity ratio of D and G peak ID/IG ratio of 1.12. Biocompatibility assays (MTT and live/dead) showed better results at lower concentrations (1mg/ml) while higher concentrations (2mg/ml) showed reduced efficacy. Antioxidant tests revealed increased DPPH scavenging activity with higher GQD concentrations and longer incubation times. The GQDs demonstrated excellent performance as fluorescent biosensors for Ni2⁺ (0.15ppm) and Fe3⁺ (0.20ppm), with high selectivity in river water samples, highlighting their potential for environmental and health applications.

A dozen predicted SiGe alloys with low enthalpies and strong absorption of sunlight for photovoltaic applications.

Silicon germanium alloy materials have promising potential applications in the optoelectronic and photovoltaic industries due to their good electronic properties. However, due to the inherent brittleness of semiconductor materials, they are prone to rupturing under harsh working environments, such as high stress or high temperature. Here, we conducted a systematic search for silicon germanium alloy structures using a random sampling strategy, in combination with group theory and graph theory (RG2), and 12 stable SiGe structures in 2-8 stacking orders were predicted. All 12 stable SiGe crystals exhibit a popular bandwidth of 1.06-1.19 eV, approaching the optimal Shockley Queisser limit (≈1.4 eV). Among these, 6 structures showed quasi-direct band gaps. Considering their potential photovoltaic applications, we systematically studied the changes in their enthalpy, stability, mechanical stability (elastic moduli), lattice parameters, band structures, and light absorption under a stress load of up to 20 GPa. These new SiGe crystals featured relatively low enthalpies (even as low as 0.009 eV per atom), and good stability and mechanical properties. In addition, the absorption spectra of these materials demonstrated a high absorption intensity for the solar spectrum that was approximately 3 times higher than that of conventional diamond silicon, even under a 20 GPa stress. The present study uses the predicted 2-8H SiGe to provide new insights into the photovoltaic applications of SiGe alloy structures.

Thermoelectrics in alkaline earth metal tellurides of ATe2 type - A first-principles study

Abstract We report an extensive study on the structural and thermoelectric performance of the novel semiconducting binary type ATe2 (A=Mg,Be,Ca,Sr,Ba) earth abundant materials using Density Functional Theory (DFT) and semi-classical Boltzmann transport theory. The PBE-GGA exchange correlation potential method was used for electronic structure calculations within the framework of density functional theory. The structural stability of the materials was confirmed by ground state energy, formation energy and mechanical responses. The calculated lattice constants, energy band structures and density of states explain the nature of the materials and are agreed with previous experimental and theoretical works. According to our calculated results, we revealed a high figure of merit materials are CaTe2 and SrTe2 due to high Seebeck and electrical conductivity and low thermal conductivity values. Additionally, Slack's equation was utilized to obtain low lattice thermal conductivity values. Our findings will serve as theoretical guidelines for future experimental and industrial applications both in cooling and heating

Mid-Infrared High-Power InGaAsSb/AlGaInAsSb Multiple-Quantum-Well Laser Diodes Around 2.9 μm.

Antimonide laser diodes, with their high performance above room temperature, exhibit significant potential for widespread applications in the mid-infrared spectral region. However, the laser's performance significantly degrades as the emission wavelength increases, primarily due to severe quantum-well hole leakage and significant non-radiative recombination. In this paper, we put up an active region with a high valence band offset and excellent crystalline quality with high luminescence to improve the laser's performance. The miscibility gap of the InGaAsSb alloy was systematically investigated by calculating the critical temperatures based on the delta lattice parameter model. As the calculation results show, In0.54Ga0.46As0.23Sb0.77, with a compressive strain of 1.74%, used as the quantum well, is out of the miscibility gap with no spinodal decomposition. The quantum wells exhibit high crystalline quality, as evidenced by distinct satellite peaks in XRD curves with a full width at half maximum (FWHM) of 56 arcseconds for the zeroth-order peak, a smooth surface with a root mean square (RMS) roughness of 0.19 nm, room-temperature photoluminescence with high luminous efficiency and narrow FHWM of 35 meV, and well-defined interfaces. These attributes effectively suppress non-radiative recombination, thereby enhancing internal quantum efficiency in the antimonide laser. Furthermore, a novel epitaxial laser structure was designed to acquire low optical absorption loss by decreasing the optical confinement factor in the cladding layer and implementing gradient doping in the p-type cladding layer. The continuous-wave output power of 310 mW was obtained at an injection current of 4.6 A and a heatsink temperature of 15 °C from a 1500 × 100 μm2 single emitter. The external quantum efficiency of 53% was calculated with a slope efficiency of 0.226 W/A considering both of the uncoated facets. More importantly, the lasing wavelength of our laser exhibited a significant blue shift from 3.4 μm to 2.9 μm, which agrees with our calculated results when modeling the interdiffusion process in a quantum well. Therefore, the interdiffusion process must be considered for proper design and epitaxy to achieve mid-infrared high-power and high-efficiency antimonide laser diodes.

Continuous Strain Modulation of Moiré Superlattice Symmetry From Triangle to Rectangle.

Moiré superlattices formed in van der Waals (vdW) bilayers of 2D materials provide an ideal platform for studying previously undescribed physics, including correlated electronic states and moiré excitons, owing to the wide-range tunability of their lattice constants. However, their crystal symmetry is fixed by the monolayer structure, and the lack of a straightforward technique for modulating the symmetry of moiré superlattices has impeded progress in this field. Herein, a simple, room-temperature, ambient method for controlling superlattice symmetry is reported. The method uses vdW heterostructures on a flexible substrate; by bending the substrate, a uniaxial strain is introduced. Based on numerical calculations, a strain condition is designed to deform the moiré superlattice from triangular to rectangular, and visualized the continuous deformation of real-space moiré superlattices using piezoresponse force microscopy. The band calculations show that nearly flat moiré minibands remain in the rectangular lattice; therefore, this method provides an additional tuning knob for the Hamiltonian of moiré quantum matter.

Dipolar wavevector interference induces a polar skyrmion lattice in strained BiFeO3 films.

Skyrmions can form regular arrangements, so-called skyrmion crystals (SkXs). A mode with multiple wavevectors q then describes the arrangement. While magnetic SkXs, which can emerge in the presence of Dzyaloshinskii-Moriya interaction, are well established, polar skyrmion lattices are still elusive. Here we report the observation of polar SkXs with a well-defined double-q state in ultrathin BiFeO3 films on LaAlO3. The compressive strain induced by the LaAlO3 substrate yields a dipolar topological texture with a periodic arrangement of skyrmions. The square-like superstructure with a lattice constant of 2.68 nm features a periodic modulation of polarization fields and topological charge density. The film furthermore exhibits an enhanced electromechanical response with an increased converse piezoelectric coefficient (d33) compared with SkX-free films. Transmission electron microscopy experiments in combination with phase-field simulations indicate that the dipole skyrmion texture results from the interference of two orthogonal single-q dipole patterns. We anticipate that the interference of multiple wavevectors may lead to a diversity of topological crystals with a variety of symmetries and lattice constants.

Nanoscale Structure and Interfacial Electrochemical Reactivity of Moiré-Engineered Atomic Layers.

ConspectusThe electronic properties of atomically thin van der Waals (vdW) materials can be precisely manipulated by vertically stacking them with a controlled offset (for example, a rotational offset─i.e., twist─between the layers, or a small difference in lattice constant) to generate moiré superlattices. In recent years, the application of this "twistronics" concept to interfacial electrochemistry has unveiled unique pathways for tailoring the electrochemical reactivity. This Account provides an overview of our work that leveraged a suite of structural characterization methods, such as interferometric four-dimensional scanning transmission electron microscopy, dark-field transmission electron microscopy, and scanning tunneling microscopy, along with nanoscale electrochemical measurement techniques, namely, scanning electrochemical cell microscopy (SECCM), to uncover and dissect the profound impact of electrode electronic structure, controlled by interlayer twist, on interfacial electron transfer kinetics. At the heart of our findings is the discovery that moiré engineering enables the isolation of thermodynamically unfavorable stacking configurations, or topological defects, that substantially increase the standard electron transfer rate constant at the solid-liquid interface beyond what has been measured on conventional, nontwisted two-dimensional (2D) materials. This enhancement in interfacial reactivity can be attributed to the localization of a high density of electronic states within these particular sites in the superlattice, a similar effect to that which occurs upon incorporation of physical defects or vacancies in an electrode material but instead using an atomically pristine surface with a highly tunable structure. Throughout our studies, understanding the nuances of the relationship between the preimposed moiré twist angle and the observed electron transfer kinetics has heavily relied on the interrogation of additional factors such as spontaneous superlattice reconstruction and three-dimensional localization of electronic states, illustrating the importance of combining electrochemical measurements with both nanoscale structural probes and theoretical modeling for designing and optimizing moiré-engineered electrodes. The insight afforded by our efforts in this space continues to deepen our understanding of the fundamental mechanisms governing electron transfer at electrochemical interfaces at large and also points to the revolutionary prospect of twistronics for advancing electrochemical technologies. While our electrochemical studies have, so far, focused largely on graphene-based moiré materials, we also offer a perspective on the promise of transition metal dichalcogenide (TMD)-based moirés as candidates for highly versatile (photo)electrode surfaces. Accordingly, we provide a discussion of our studies on the structural relaxation observed in moiré superlattices of TMDs, and we summarize our work combining SECCM with field-effect electrostatic gating of TMDs to deconvolute the influences of material conductivity and intrinsic electron transfer kinetics from the overall electrochemical response of a semiconducting 2D material. Overall, this body of work establishes a distinctive foundation for the design of a wide range of materials with tailored properties that can provide crucial insights into interfacial charge transfer chemistry─potentially serving as platforms for sensing, energy conversion, and electrocatalysis─in addition to the emergent exotic correlated electron physics that originally ignited intense interest in moiré twistronics.

Optimizing FeS crystallinity of sulfidated nZVI to enhance electron transport capacity for clothianidin efficient degradation: Regulation of biochar pyrolysis temperature.

Clothianidin (CTD), a highly watersoluble neonicotinoid insecticide, easily enters water through runoff. Developing eco-friendly materials to degrade CTD is essential. Nano zero valent iron (nZVI) is effective for contaminant removal, but it deactivates due to agglomeration. Biochar supported sulfidated nano zero valent iron (S-nZVI-BC) can effectively mitigate nZVI aggregation while enhancing anti-passivation and electron transfer. However, the regulation of BC preparation conditions on S-nZVI-BC performance and contaminant degradation mechanism remains elusive. This work systematically investigated the effects of BC pyrolysis temperature on FeS formation in S-nZVI-BC and CTD degradation mechanism. BC enhanced FeS crystallinity and increased Fe0 lattice constants, facilitating electron transfer. Compared to S-ZVI, the CTD removal kinetics constants of S-nZVI-BC was 2.30 folds higher. Competitive dynamics model revealed BC pyrolysis temperature and S modulated the competition between O2 and CTD, enhancing electron utilization efficiency and improving nZVI anti-passivation under oxic conditions. Quenching experiment and electrochemical tests indicated S incorporation and changes in BC pyrolysis temperature modulated nZVI active reduced species (H*) production and contribution to CTD degradation. Additionally, increasing FeS crystallinity by adjusting BC pyrolysis temperature improved the electron transfer efficiency of S-nZVI-BC, enabling efficient CTD degradation. Density functional theory (DFT) calculations revealed CTD preferentially underwent nitro-reduction over dechlorination. All these findings can provide guidance for the application of S-nZVI-BC.

Infinite Organic Solid-Solution Semiconductors with Continuous Evolution in Film Morphology, Crystalline Lattice and Electrical Properties.

Constructing a solid solution is an effective strategy for regulating the properties of composite organic semiconductors. However, there presents significant challenges in fabrication and understanding of organic solid-solution semiconductors. In this study, infinite solid-solution semiconductors are successfully achieved by integrating rod-like organic molecules, thereby overcoming the limitations of current organic composite semiconductors. Within these solid solutions, one type of molecule are incorporated into the crystalline lattice of another through random substitution. The continuous evolution in film morphology, crystalline lattice parameters and physical properties are observed as component ratios vary, accompanying with changes in the growth behavior of films. Molecular-level intercalation is evidenced by Davydov splitting, photoluminescence spectroscopy, and optical absorption analyses. Moreover, the continuous variation in ionization potential is demonstrated through organic Schottky diodes. This advancement in organic solid solutions can not only satisfy diverse requirements for device fabrication but also facilitate novel designs in device architecture.

About the Rare-Earth Metal(III) Bromide Oxoarsenates(III) RE5Br3[AsO3]4 with A- (RE = La and Ce) or B-Type Structure (RE = Pr, Nd, Sm–Tb) and RE3Br2[AsO3][As2O5] (RE = Y, Dy–Yb)

The monoclinic rare-earth metal(III) bromide oxoarsenates(III) RE5Br3[AsO3]4 of the A-type (RE = La and Ce) crystallize in the space group C2/c with the lattice parameters a = 1834.67(9) pm, b = 553.41(3) pm, c = 1732.16(9) pm and β = 107.380(3)° for La5Br3[AsO3]4 and a = 1827.82(9) pm, b = 550.67(3) pm, c = 1714.23(9) pm and β = 107.372(3)° for Ce5Br3[AsO3]4 with Z = 4, while, for the B-type (RE = Pr, Nd and Sm–Tb), they prefer the space group P2/c with lattice parameters from a = 881.23(5) pm, b = 547.32(3) pm, c = 1701.14(9) pm and β = 90.231(3)° for Pr5Br3[AsO3]4 to a = 875.71(5) pm, b = 535.90(3) pm, c = 1643.04(9) pm and β = 90.052(3)° for Tb5Br3[AsO3]4 with Z = 2. The closely related rare-earth metal(III) bromide oxoarsenates(III) RE3Br2[AsO3][As2O5] crystallize in the triclinic space group P1¯ with lattice parameters from a = 539.15(4) pm, b = 870.68(6) pm, c = 1092.34(8), α = 90.661(2)°, β = 94. 792(2)° and γ = 90.223(2)° for Dy3Br2[AsO3][As2O5] to a = 533.56(4) pm, b = 869.61(6) pm, c = 1076.70(8), α = 90.698(2)°, β = 94.785(2)° and γ = 90.053(2)° for Yb3Br2[AsO3][As2O5] with Z = 2. All three structures have the same building units with [REO8]13− and [REO4Br4]9− polyhedra as well as isolated ψ1-tetrahedral [AsO3]3− anions in common, with the exception that, in the latter two, ψ1-[AsO3]3− tetrahedra linked by a corner form a pyroanionic [As2O5]4− entity. A- and B-type differ in the stacking sequence of their 2∞{[(RE3)Ot4/1(Br1)v1/2(Br2)e3/3]6.5−} layers. While the former have an ABC sequence, the latter exhibit an AAA variant. In the triclinic structures, the (RE3)3+ sites are thinned out, while the As3+ sites are simultaneously enriched, resulting in the mentioned condensed units.

Unveiling the Electrocatalytic Performances of the Pd-MoS2 Catalyst for Methanol-Mediated Overall Water Splitting

Herein, this work elucidates the synthesis of the Pd-MoS2 catalyst for application in methanol-mediated overall water splitting. The scanning electron microscope (SEM) and transmission electron microscope (TEM) pictures offer an exciting nanostructured shape of the Pd-MoS2, depicting a high surface area. Further, high-resolution TEM (HRTEM) pictures confirm the lattice plane (100), lattice spacing (0.26 nm), and hexagonal crystal structure of the Pd-MoS2. Moreover, high-angle annular dark-field (HAADF) images and related color maps disclose the Mo, S, and Pd elements of the Pd-MoS2. The Pd-MoS2 catalyst exhibits lower overpotentials of 224.6 mV [methanol-mediated hydrogen evolution reaction (MM-HER)] at −10 mA cm−2 and 133 mV [methanol-mediated oxygen evolution reaction (MM-OER)] at 10 mA cm−2. Further, the Pd-MoS2 illustrates noteworthy stability for 15.5 h for MM-HER and 18 h for MM-OER by chronopotentiometry test. Excitingly, the Pd-MoS2∥Pd-MoS2 cell reveals a small potential of 1.581 V compared to the MoS2∥MoS2 cell (1.648 V) in methanol-mediated overall water splitting. In addition, the Pd-MoS2∥Pd-MoS2 combination reveals brilliant durability over 18 h at 10 mA cm−2.

Adsorption of lithium, sodium, gallium, and sulfur atoms onto a GaS monolayer

Abstract Hexagonal gallium sulfide (GaS) monolayer is a very promising monochalcogenide for applications such as electronics, optoelectronics, and catalysts. The adsorption and the diffusion of lithium (Li), sodium (Na), gallium (Ga), and sulfur (S) atoms onto the 2 × 2-GaS hexagonal monolayer are investigated using density functional theory (DFT), along with atomic pseudopotentials. The values of the calculations for the adsorption energy show that the energetically most favorable site for the Li, Na, and Ga adsorbates is the H site, while the most energetically favorable site for the S adsorbate is the TS site. The values calculated for the adsorption energy at the energetically most favorable sites for the Li, Na, Ga, and S atomic adsorbates are −1.853 eV, −1.378 eV, −1.028 eV, and −1.525 eV, respectively. Analysis of the structural properties revealed that after the adsorption process, the GaS+ads system maintains its structure and geometry, since the lattice constants and the lGa-Ga, lGa-S, and lS-S bond lengths do not change significantly with respect to the pristine monolayer. The diffusion of Li, Na, Ga, and S atoms on the 2 × 2-GaS monolayer’s surface shows energy barriers of 28 meV, 40 meV, 72 meV, and 161 meV, respectively. From the total density of states (DOS), it is established that in all cases the GaS+ads monolayer system acquires metallic behavior. Finally, analysis of the Bader charge of the GaS+ads system just at the energetically most favorable sites shows that the Li and Na atoms transfer charge to the monolayer (cations), becoming ionized, while the Ga and S atoms transfer and gain charge from the monolayer, respectively, becoming partially ionized. This electronic behavior makes the GaS monolayer a promising material for use as an anode in batteries.

Crystal Structure and Magnetic Properties of the Novel Compound ErMn5Ge3.

The RE-M-Ge systems (RE: rare earths, M: transition group elements) contain a large number of compounds with special magnetic properties. A novel compound ErMn5Ge3 was found during the investigation on the phase diagram of the Er-Mn-Ge ternary system, and its crystal structure and magnetic properties were investigated. Powder X-ray diffraction results show that ErMn5Ge3 crystallizes in an orthorhombic YNi5Si3-type structure with the space group Pnma (No. 62) and the lattice parameters of a = 13.0524(6) Å, b = 3.8853(7) Å, and c = 11.4027(4) Å. The magnetization curves and isothermal magnetization curves from 100 to 300 K were measured for ErMn5Ge3. Magnetic tests showed that the compound was weakly magnetic and had a Curie temperature of 304 K. It is believed that its magnetic properties are determined by Mn atoms, which are surrounded by a complex environment, leading to uncertainty in the direction of the magnetic moment and hence poor magnetic ordering. This uncertainty simultaneously leads to a significant separation of the ZFC and FZ curves. First-principles calculations confirm that the magnetic properties of ErMn5Ge3 are mainly provided by the Mn atoms, and its magnetic moment is calculated to be about 4.5 μB. A possible magnetic structure model with simultaneous Mn-Mn ferromagnetic/antiferromagnetic coupling is constructed based on the Mn atom spacing, which can well explain the magnetic performance of ErMn5Ge3.

Ab-initio trained machine learning potential for MAX compound Ti2AlC: Construction, validation, and study of non linear elasticity

Abstract One of the intriguing features exhibited by the layered MAX phase compounds, is the non linear elastic behaviour. Since the experimental observation of this curious behaviour, the underlying micro-mechanism has been discussed to interpret experimental observations. However, the theoretical investigation remained a challenge due to the associated length and time scales of the phenomena. In the present work, we adopt a data driven approach to develop a machine learned interatomic potential for the MAX compound Ti$_2$AlC following the Moment Tensor Potential protocol. The constructed potential is validated in lattice constant, formation energy, elastic constant, and stacking fault energies. Finally, applying machine learned potential in classical molecular dynamics provides a faithful
representation of the experimentally observed non linear elasticity for Ti$_2$AlC. The generated atomic configurations confirm the proposal of formation of ripplocations which allow atomic layers to glide relative to each other without breaking the in-plane bonds. We find common defects, like Al vacancy, strongly influence the hysteresis properties of the stress-strain curve, paving the route to defect-engineered non linear elasticity.

Doping-induced enhancement of Curie temperature in Zn2Ru1−xAxMn (A = Ti, Mn, Co, Zr, and Rh) Heusler alloys: An ab initio investigation

This study examines the structural stability, electronic, and magnetic properties of off-stoichiometric Zn2Ru1−xAxMn Heusler alloys (with, A = Ti, Mn, Co, Zr, and Rh) using first-principles calculations. We find that the L21 phase is more stable than the XA phase across both ordered and disordered configurations. The variations in lattice parameters with off-stoichiometry are attributed to the atomic radii of the dopants. Our results indicate that Zn2Ru1−xAxMn alloys exhibit ferromagnetic metallic behavior, driven primarily by Mn-Mn, Ru-Mn, and A-Mn exchange interactions. These interactions are further analyzed to calculate the Curie temperature using the mean-field approximation. The Curie temperature for Zn2RuMn is found to be approximately 300 K, which increases to 428 K upon Co doping. Our findings suggest that doping provides a means to control the Curie temperature, offering substantial potential for applications in room-temperature magnetocaloric materials and shape memory alloys. This tunability enhances the functional versatility of these alloys, making them promising candidates for future technological applications.

Effect of Dy3+ Ions on Structural, Thermal and Spectroscopic Properties of L-Threonine Crystals: A Visible Light-Emitting Material

In this study, L-threonine crystals (L-thr) containing Dy3+ ions (L-thrDy5 and L-thrDy10) with varying mass concentrations (5% and 10%) were successfully synthesized using a solvent slow evaporation method. The structural properties were characterized by Powder X-ray diffraction and Rietveld refinement. The data revealed that all three samples crystallized in orthorhombic symmetry (P212121-space group) and presented four molecules per unit cell (Z = 4). However, the addition of Dy3+ ions induced a dilation effect in the lattice parameters and cell volume of the organic structure. Additionally, the average crystallite size, lattice microstrain, percentage of void centers, and Hirshfeld surface were calculated for the crystals. Thermogravimetric and differential thermal analysis experiments showed that L-thr containing Dy3+ ions are thermally stable up to 214 °C. Fourier transform infrared and Raman spectroscopy results indicated that the Dy3+ ions interact indirectly with the L-thr molecule via hydrogen bonds, slightly affecting the crystalline structure of the amino acid. Optical analysis in the ultraviolet–visible region displayed eight absorption bands associated with the electronic transitions characteristic of Dy3+ ions in samples containing lanthanides. Furthermore, L-thrDy5 and L-thrDy10 crystals, when optically excited at 385 nm, exhibited three photoluminescence bands centered around approximately 554, 575, and 652 nm, corresponding to the 4F7/2 → 6H11/2, 4F9/2 → 6H13/2, and 4F9/2 → 6H11/2 de-excitations. Therefore, this study demonstrated that L-thr crystals containing Dy3+ ions are promising candidates for the development of optical materials due to their favorable physical and chemical properties. Additionally, it is noteworthy that the synthesis of these systems is cost-effective, and the synthesis method used is efficient.