Lattice Parameters Research Articles

Revealing the materials, design, and performance of Ni-rich LiNi1-x-yCoxMnyO2/graphite pouch cells

Among lithium-ion batteries (LIBs), Ni-rich LiNi1-x-yCoxMnyO2/Graphite batteries hold a dominant position in electric vehicles due to high energy density, good cycling stability, and low content of Co element. In this work, Ni-rich LiNi1-x-yCoxMnyO2 (LiNi0.83Co0.07Mn0.10O2, NCM83)/Graphite pouch cells with a capacity of around 2.1 Ah are designed and manufactured. The structure and micromorphology of NCM83 as well as graphite are revealed. The XRD Rietveld refinement method clarifies the lattice parameters of NCM83. The PE separator modified by Al2O3 and PVDF (PE/Al2O3/PVDF) is used in the cells. The design parameters, formation, and aging processes are disclosed as well. Charge-discharge tests demonstrate that the NCM83/Graphite pouch cells have good electrochemical performance. Notably, the cell delivers an initial discharge capacity of 2.158 Ah at 1 A and 25 °C, and retains a high reversible discharge capacity of 1.715 Ah after 500 cycles with a capacity retention of close to 80 %. Additionally, the polarization characteristics during charging and discharging are discussed in detail, demonstrating that a good linear relationship exists between polarization voltage and cycle number. This work systematically reveals the materials, and design technology of NCM83/Graphite battery cells and helps deepen the understanding of commercial LIBs based on Ni-rich LiNi1-x-yCoxMnyO2 cathode materials.

Characterization of Kazakhstan’s Clays by Mössbauer Spectroscopy and X-ray Diffraction

Studies of the mineralogical composition were carried out, and the features of the clays from the deposits of Kazakhstan were established using Mössbauer spectroscopy (MS) and X-ray diffraction analysis (XRD). According to the XRD results, all the samples were mixed-layer clays of the kaolinite–illite type. The lattice parameters of the kaolinite were determined, and it was shown that its structure was disordered and contained a certain amount of impurity in some of the clay samples. A special feature of two of the samples was the additionally identified muscovite polytype 2M1. The spectra of the iron-containing clays were amenable to being resolved into separate components, with similar Mössbauer parameters of the kaolinite, muscovite, illite, and glauconite. The oxidation state of the iron was determined using MS. The predominant part of paramagnetic iron in most samples was in the trivalent state. The primary minerals contributing to Fe2+ were illite and muscovite. The results obtained during the study of the clay samples with complex mineralogical compositions using MS and XRD methods both complemented one another and were found to be in good agreement.

Studies of Structural, Optical, and Raman Analysis of Ni‐Substituted CoFe2O4

The polycrystalline ferrite samples of NixCo1−xFe2O4 (x = 0.1, 0.3, 0.5, 0.7, and 0.9) are synthesized through the well‐known sol–gel method. The X‐ray diffraction (XRD) pattern confirms the cubic single‐phase spinel structure. Rietveld refinement indicates the absence of any other impurity phases in the samples. Additionally, XRD analysis reveals variations in lattice parameters corresponding to the doping. The Debye Scherer formula has been used to calculate the crystallite size of the samples, the crystallite size of the samples existing in the nanoregime. The results from field emission scanning electron microscopy confirm the morphological structure of the prepared samples. Additionally, the energy‐dispersive X‐ray spectra confirm the elemental composition and purity of the synthesized samples, validating the appropriateness of doping in the polycrystalline samples. The Raman spectra give the information about the vibrational modes in the sample. The Fourier transform infrared rays spectrum shows that the samples have a broad range of chemical interactions. The photoluminescence spectroscopy (PL) suggests strong luminescence in the visible range. PL spectroscopy provides that PL intensity decreases with increasing excitation wavelength due to nanosize of the particle.

Pressure effect on the structural, electronic, mechanical, optical and thermal properties of Ga2TiX6 (X = Cl, Br): A DFT simulation

The pressure effect on the physical properties of Ga2TiX6(X = Cl, Br) has been carried out through density function theory (DFT) accomplished via CASTEP guidelines. At ambient condition the structural aspects of Ga2TiX6(X = Cl, Br) show well accord with the previous theoretical data. A dramatically decrease of lattice constants, cell volumes and bond length with pressure is perceived. The negative enthalpy energy ensured the chemical formation of Ga2TiX6(X = Cl, Br). The positive stiffness constants (Cij) ensure the mechanical stability of Ga2TiX6(X = Cl, Br) at ambient and hydrostatic pressure. Moreover, the fundamental polycrystalline factors of phases Ga2TiX6(X = Cl, Br) such as bulk, shear and Young’s moduli, Poisson’s and Pugh’s fraction, machinability index as well as hardness of these materials have been calculated and discussed at ambient and hydrostatic pressure. Having very low values of bulk modulus (<100 GPa) they can be considered as soft materials. The increase of machinable index with pressure ensure the high lubricating properties, low friction, and high plastic strain of Ga2TiX6(X = Cl, Br) and also ensure their possible industrial applications. Band structure analysis ensure the semiconducting nature of Ga2TiX6(X = Cl, Br) at ambient condition but the semiconducting nature shift to metallic manner at 55 GPa and 65 Gpa respectively. The decrease of total density of states is observed at high pressure. The creation of new bond at high pressure is also observed in materials Ga2TiX6(X = Cl, Br). The investigated optical features ensured that the studied phases can be used in UV photodiodes, and UV light emitters since they revel intense peaks at UV region. Very low Debye temperature, melting temperature and thermal conductivity are observed at ambient condition which ensures that the compounds Ga2TiX6(X = Cl, Br) can be used as thermal barrier coating materials (TBC).

Analysis Lattice Constant of Ceramic SrTiO3 Doped Cuprum(II) Acetate Cube Structure by Cramer-Cohen Method

Analysis of SrTiO&lt;sub&gt;3&lt;/sub&gt; ceramics with the doping Cuprum(II) acetate (Cu(CH&lt;sub&gt;3&lt;/sub&gt;COO)&lt;sub&gt;2&lt;/sub&gt;), the variation in the concentration of doping used 0%; 0,5%; and 1% using the solid state reaction method was successful. The annealing process is carried out starting from room temperature then raised to an annealing temperature of 850 &lt;sup&gt;o&lt;/sup&gt;C with a temperature increase of 1,67 &lt;sup&gt;o&lt;/sup&gt;C / minute and held constant for 8 hours. Next proceed with the cooling process until it returns to room temperature for 13 hours. Analysis of XRD data using the Cramer-Cohen method yielded a lattice parameter of 3,909 Å; 3,906 Å; and 3,905 Å, a cubic crystal structure.

The effect of synthesis temperature on structural, morphological, and band gap energy of plate-like Bi4Ti2.95V0.05O12 prepared by molten NaCl/KCl salt method

Vanadium (V)-doped Bi4Ti3O12 compound is reported to have good photocatalyst properties; however, efforts still need to improve the ability of the photocatalyst through various strategies, such as controlling the morphology and particle size. The molten salt method is one of the simple synthesis methods reported successful in synthesizing Bi4Ti3O12 compounds with plate-like/sheet morphology and reported having good photocatalyst activity. One of factor influenced to particle compound obtained by molten salt method is synthesis temperature. Therefore, in this work, V-doped Bi4Ti3O12 (Bi4Ti2.95V0.05O12) was prepared through the molten salt NaCl/KCl method at various synthesis temperatures: 700, 750, and 800?C and the effect of temperature synthesized on (a) structural (b) morphological, and (c) band gap energy were studied. These studies used X-ray diffraction data (diffractogram), scanning electron microscope (SEM) and diffuse reflectance ultraviolet-visible spectroscopy. The diffractograms showed that the target compound was successfully obtained at all temperature synthesis. The crystallographic data indicated that temperature synthesis determined the lattice parameter values. However, there are no clear trend changes that is possibly due to changes in the valence of the V atom. The synthesis temperature also causes increasing the crystallite size but does not affect the crystallinity samples. SEM images showed that all samples had plate-like/sheets morphology and the particle size became larger at higher temperature. It indicated that the particle growth rate was faster than nucleation rate. Meanwhile, the result of Kubelka-Munk calculation showed that all samples had relatively same band gap energy value (Eg(1) was ~ 2.90, and Eg(2) was ~1.85 eV.

An automated protocol to construct flexibility parameters for classical forcefields: applications to metal-organic frameworks.

In this work, forcefield flexibility parameters were constructed and validated for more than 100 metal-organic frameworks (MOFs). We used atom typing to identify bond types, angle types, and dihedral types associated with bond stretches, angle bends, dihedral torsions, and other flexibility interactions. Our work used Manz's angle-bending and dihedral-torsion model potentials. For a crystal structure containing N atoms in its unit cell, the number of independent flexibility interactions is 3(N atoms - 1). Because the number of bonds, angles, and dihedrals is normally much larger than 3(N atoms - 1), these internal coordinates are redundant. To reduce (but not eliminate) this redundancy, our protocol prunes dihedral types in a way that preserves symmetry equivalency. Next, each dihedral type is classified as non-rotatable, hindered, rotatable, or linear. We introduce a smart selection method that identifies which particular torsion modes are important for each rotatable dihedral type. Then, we computed the force constants for all flexibility interactions together via LASSO regression (i.e., regularized linear least-squares fitting) of the training dataset. LASSO automatically identifies and removes unimportant forcefield interactions. For each MOF, the reference dataset was quantum-mechanically-computed in VASP via DFT with dispersion and included: (i) finite-displacement calculations along every independent atom translation mode, (ii) geometries randomly sampled via ab initio molecular dynamics (AIMD), (iii) the optimized ground-state geometry using experimental lattice parameters, and (iv) rigid torsion scans for each rotatable dihedral type. After training, the flexibility model was validated across geometries that were not part of the training dataset. For each MOF, we computed the goodness of fit (R-squared value) and the root-mean-squared error (RMSE) separately for the training and validation datasets. We compared flexibility models with and without bond-bond cross terms. Even without cross terms, the model yielded R-squared values of 0.910 (avg across all MOFs) ± 0.018 (st. dev.) for atom-in-material forces in the validation datasets. Our SAVESTEPS protocol should find widespread applications to parameterize flexible forcefields for material datasets. We performed molecular dynamics simulations using these flexibility parameters to compute heat capacities and thermal expansion coefficients for two MOFs.

Step height measurement of monoatomic silicon crystal lattice steps with a commercial atomic force microscope

Abstract Precise control of advanced materials relies on accurate dimensional metrology at the sub-nanometre scale. At this scale, the accuracy of scanning probe microscopy (SPM) has been limited by the lack of traceable transfer standard artefacts with calibration structures of suitable dimensions. With the adoption in 2019 of the silicon crystal lattice spacing as a secondary realization of the metre in the International System of Units (SI), SPM users have direct access to a realization of the SI metre at the sub-nanometre level by means of the step height of self-assembled monatomic lattice steps that can form on the surface of silicon crystals. A key challenge of successfully adopting this pathway is establishing the need for established protocols to minimize measurement errors and artifacts in routine laboratory use.&amp;#xD;In this study, step height measurements of monoatomic lattice steps in an ordinal/staircase structure on a Si(111) crystal surface have been derived from images acquired with a commercially available, research-level atomic force microscope (AFM). Measurement results derived from AFM images using three different SPM image processing and analysis software packages are compared. Significant sources of measurement uncertainty are identified; principally the contribution from the dependence on scan direction. The calibration of the&amp;#xD;AFM derived from this measurment was used to traceably measure the sub-nanometre lattice steps on a silicon carbide crystal surface to demonstrate the viability of this calibration pathway.&amp;#xD;

Sheep Bone Ultrastructure Analyses Reveal Differences in Bone Maturation around Mg-Based and Ti Implants.

Magnesium alloys are some of the most convenient biodegradable materials for bone fracture treatment due to their tailorable degradation rate, biocompatibility, and mechanical properties resembling those of bone. Despite the fact that magnesium-based implants and ZX00 (Mg-0.45Zn-0.45Ca in wt.%), in particular, have been shown to have suitable degradation rates and good osseointegration, knowledge gaps remain in our understanding of the impact of their degradation properties on the bone's ultrastructure. Bone is a hierarchically structured material, where not only the microstructure but also the ultrastructure are important as properties like the local mechanical response are determined by it. This study presents the first comparative analysis of bone ultrastructure parameters with high spatial resolution around ZX00 and Ti implants after 6, 12, and 24 weeks of healing. The mineralization was investigated, revealing a significant decrease in the lattice spacing of the (002) Bragg's peak closer to the ZX00 implant in comparison to Ti, while no significant difference in the crystallite size was observed. The hydroxyapatite platelet thickness and osteon density demonstrated a decrease closer to the ZX00 implant interface. Correlative indentation and strain maps obtained by scanning X-ray diffraction measurements revealed a higher stiffness and faster mechanical adaptation of the bone surrounding Ti implants as compared to the ZX00 ones. Thus, the results suggest the incorporation of Mg2+ ions into the bone ultrastructure, as well as a lower degree of remodeling and stiffness of the bone in the presence of ZX00 implants than Ti.

Experimental Validation of Property Models and Databases for Computational Superalloy Design

Computational superalloy development is a powerful alternative to the conventional experimental approach. Based on thermodynamic databases and the CALPHAD method, it is possible to estimate the properties of a large number of potential alloys and select the most promising ones. However, the accuracy of the databases and complementary property models can be unsatisfying. The accuracy of two mass density and lattice parameter models and the TTNI8 and TCNI10 databases is analyzed in detail on the experimental basis of computationally optimized single‐crystalline superalloys. Various properties are measured and compared to the results of the property models and databases. Neither of the databases is superior to the other and especially the solvus temperature is not accurately described in both. The new mass density model, a linear regression based on the molar mass, is more reliable for low‐density alloys. Both lattice parameter model versions slightly overestimate the room‐temperature lattice parameter. The lattice parameter, however, is more accurately calculated using the new model version. The results of this study can be readily used to improve a multicriteria alloy optimization tool for computational superalloy design.

Thermodynamic and elastic properties of laves phase AB2-based alloys and their hydrides: A density functional theory (DFT) study

A first-principles method based on the density functional theory (DFT) was employed in conjunction with quasi-harmonic Debye model to investigate the structural, elastic, and thermodynamic properties of a series of AB2-based Laves phases alloys and their hydrides. Simulation results revealed that the studied materials possess the Laves phase structure with lattice parameters comparable to experimental findings. For the first time, to the best of our knowledge, mixing entropy determined using Debye model was used to classify alloys into (Low- Medium-High Entropy Alloys) LEA, MEA and HEA categories rather than the commonly used ideal solution model, which is often inaccurate and ignores the impact of temperature. Lattice analyses of the alloy materials indicated that cell volume increases with the addition of elements, while the enthalpy of hydride formation indicates that hydrogen absorption in these alloys is exothermic and that the 3.00 H/F.U configuration is energetically stable. The alloys and their hydrides are metallic with no band gap at the Fermi level. The thermodynamic properties were studied using the quasi-harmonic Debye model and it was found that Bulk modulus decreases with increasing volume, and the hydrides possess lower bulk modulus compared to their metallic counterparts. Moreover, Debye temperature decreases with the gradual addition of elements, indicating weaker chemical bonds in ternary and other alloys. All hydrides have lower Debye temperature than their parent alloy materials. Finally, The alloys are classified into low-, medium-, and high-entropy alloys based on mixing entropy calculated using the Debye model. TiMn2 is classified as a low-entropy alloy, ZrMn2, Ti0.5Zr0.5Mn2, and Ti0.5Zr0.5MnFe as medium-entropy alloys, and Ti0.5Zr0.5(MnCr)2, Ti0.5Zr0.5Mn2/3Fe2/3Cr2/3, and Ti0.5Zr0.5Mn0.5Fe0.5Cr0.5Ni0.5 as high-entropy alloys.

Digging into the Intrinsic Negative Thermal Expansion of Uranium Tetrafluoride.

The intrinsic negative thermal expansion of UF4 below room temperature was examined. A redetermination of the structure of UF4 by single-crystal X-ray diffraction at 100, 200, and 300 K accompanied by an evaluation of the atomic displacement parameters (ADPs) of the F atoms was performed. The structure of UF4 was described as the stacking of two subnetworks, respectively, constituted by the U(1) and U(2) atoms. The subnetwork formed by the U(2) atoms consists of infinite layers that run parallel to the (b, c) plan. The layers are composed of infinite zigzag chains of corner-sharing U(2)F8 polyhedra running along the c-axis. An increase of temperature from 100 to 300 K leads to a decrease of the unit cell volume and the a and c lattice parameters and an increase of the b lattice parameter. As the temperature increases, the intrachain, interchain, and interlayer U-U distances decrease. It is proposed that the decrease of the intrachain and interlayer U-U distances causes a contraction of the U(2) subnetwork along the a- and c-axis and that a translation of the chains along the c-axis causes an expansion along the b-axis. Analysis of the ADPs of the F atoms indicates that a guitar string effect in the U-F-U units is possibly the origin of the decrease in the U-U distances. A correlation between the U-U distances and the magnitude of the ADPs of the F atoms was established.

Influence of cobalt doping on structural, optical, and electrical properties of zinc oxide nanoparticles prepared by polymeric precursor method

Cobalt-doped ZnO nanoparticles at different compositions have been obtained by the polymeric precursor method. The nanoparticles were obtained at the working pH from 8.3 to 8.5 and synthesized at 550 °C. The properties were studied using X-ray diffraction (XRD), vibrational spectroscopy (FTIR/Raman), diffuse reflectance absorbance spectroscopy (DR UV–Vis), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM/EDS), and impedance spectroscopy. The lattice parameters were determined at room temperature by Rietveld refinement, confirming single-phase composition with a hexagonal wurtzite structure. FTIR and Raman analyzes identified the characteristic vibrations of the synthesized system and the typical deformations of the wurtzite-type hexagonal structure, corroborating the results obtained from XRD. A redshift in the optical energy band gap (Egopt) was observed with increasing cobalt content compared to the ZnO sample. Considering the doping percentage, Egopt value varied between 3.13 eV and 3.04 eV for pure ZnO and Co-doped ZnO with 5 at. %., indicating that the optical properties of the nanoparticles were affected by dopant concentration. PL and SEM/EDS characterization were used to determine the associated defects for each sample and the morphology and composition of the nanoparticles. PL results showed a strong blue emission at around 439 nm (2.83 eV), which is redshift with cobalt content (ΔE between 0.05 eV and 0.01 eV), attributed to the surface defects present in the doped samples. Conductivity analysis to temperature revealed a semiconductor behavior for all samples, and their respective activation energies determined. The results provide an easy method to obtain Co-doped ZnO nanoparticles with interesting properties for optoelectronics devices.

MoS2-assisted growth of highly-oriented AlN thin films by low-temperature van der Waals epitaxy

Aluminum nitride (AlN) is a wide bandgap material used in acoustic devices, piezo- micro-electromechanical system and is promising for other electronic applications. However, for most applications, the AlN crystalline quality obtained by PVD or MOCVD is insufficient, and suitable growth substrates providing an adapted lattice match and coefficient of thermal expansion are limited. Alternatively, monocrystalline AlN wafers are not yet available in 200/300 mm sizes and suffer from high costs and quality issues. Here, we propose a novel approach involving a two-dimensional transition metal dichalcogenide (TMD) material as a seed layer, which displays an excellent lattice matching with AlN (&amp;gt;98%) allowing a strong enhancement in the c axis texture of sputtered AlN layers on Si(100)/SiO2 thermal oxide (500 nm) substrates. We have successfully demonstrated an eightfold improvement of the AlN (002) rocking curve compared to reference samples grown on thermal SiO2, thus providing a relevant and cost-effective process for the large-scale deployment of high-quality III-N materials on silicon-based substrates.

Toroidal dipole bound states in the continuum in asymmetric dimer metasurfaces

Structural symmetry plays a pivotal role in the emergence of symmetry-protected bound states in the continuum (BICs), often observed at the Γ-point within the first Brillouin zone. However, structural symmetry is not an absolute requirement for the formation of BICs at the Γ-point. In this work, we demonstrate that all-dielectric metasurfaces and photonic crystal slabs, made of dimer nanostructures with different sizes and shapes, can sustain BICs at the Γ-point. We show that the nature of these BICs is well preserved, irrespective of the size mismatch/difference, as long as the center-to-center distance between two nanodisks is equal to half of the lattice constants of a superunit cell. The BICs are transformed into quasi-BICs (QBICs) with finite quality (Q) factors by varying the interspacing of dimer nanodisks. Multipole decomposition indicates that this BIC is primarily governed by a toroidal dipole, with a secondary contribution from a magnetic dipole and magnetic quadrupole. Furthermore, we establish that such a BIC is robust against the shape of nanodisks. Notably, we observe that the Q-factor of QBICs for right nanodisks displaced along the y-axis is three orders of magnitude higher than those along the x-axis, suggesting an effective approach to realizing ultrahigh-Q resonances. Finally, we present an experimental demonstration of such a BIC by fabricating silicon dimer metasurfaces and photonic crystal slabs with dimer nanoholes. The trend of measured Q-factors and resonant wavelengths of QBICs shows good agreement with theoretical predictions. The maximum Q-factor is up to 22 633. These results not only advance our understanding of BICs within compound metasurfaces but also hold great promise in enhancing light–matter interactions.

Anharmonic and quantum effects in Pm3̄ AlM(M = Hf, Zr)H6 under high pressure: A first-principles study.

First-principles calculations were employed to investigate the impact of quantum ionic fluctuations and lattice anharmonicity on the crystal structure and superconductivity of Pm3̄ AlM(M = Hf, Zr)H6 at pressures of 0.3-21.2GPa (AlHfH6) and 4.7-39.5GPa (AlZrH6) within the stochastic self-consistent harmonic approximation. A correction is predicted for the crystal lattice parameters, phonon spectra, and superconducting critical temperatures, previously estimated without considering ionic fluctuations on the crystal structure and assuming the harmonic approximation for lattice dynamics. The findings suggest that quantum ionic fluctuations have a significant impact on the crystal lattice parameters, phonon spectra, and superconducting critical temperatures. Based on our anharmonic phonon spectra, the structures will be dynamically stable at 0.3GPa for AlHfH6 and 6.2GPa for AlZrH6, ∼6 and 7GPa lower than pressures given by the harmonic approximation, respectively. Due to the anharmonic correction of their frequencies, the electron-phonon coupling constants (λ) are suppressed by 28% at 11GPa for AlHfH6 and 22% at 30GPa for AlZrH6, respectively. The decrease in λ causes Tc to be overestimated by ∼12K at 11GPa for AlHfH6 and 30GPa for AlZrH6. Even if the anharmonic and quantum effects are not as strong as those of Pm3̄n-AlH3, our results also indicate that metal hydrides with hydrogen atoms in interstitial sites are subject to anharmonic effects. Our results will inevitably stimulate future high-pressure experiments on synthesis, structural, and conductivity measurements.

Zirconium effect on the lithiation mechanism of LiNi0.83Mn0.05Co0.12O2 positive electrode material

Ni-rich LiNi1-x-yMnxCoyO2 (x + y ≤ 0.2) materials are employed to enhance the energy density of lithium-ion batteries, while they are still facing the stability issue. Doping is considered as an efficient approach to improve the stability of the LiNi1-x-yMnxCoyO2 materials. A considerable number of studies have concluded that Zr-doping improves the stability when undoped and doped LiNi1-x-yMnxCoyO2 materials are lithiated under the same conditions. Unfortunately, a fundamental understanding of the Zr dopants role during lithiation conditions is still lacking. This work investigates the Zr effects on lithiation mechanism of LiNi0.83Mn0.05Co0.12O2 (NMC). The main findings are: First, the NMC and Zr-doped NMC have different lattice parameter growth speeds, and the (003) & (101) lattice planes form order structures at lower temperatures during lithiation process when the dopant is included. Second, Zr is prone to locate near the surface region of NMC secondary particles. Third, when lithiation time increases from 8 h to 12 h at 800 °C, the undoped NMC electrochemical performance deteriorates whereas the doped material improves. These findings highlight that understanding the mechanism behind lithiation conditions is essential for doped LiNi1-x-yMnxCoyO2. The insights revealed in this work can guide for design of other dopants for Ni-rich positive electrode materials.

Optoelectronic, thermoelectric and 3D-Elastic properties of lead-free inorganic perovskites CsInZrX6 (I, Cl and Br) for optoelectronic and thermoelectric applications

Halide perovskite materials have recently gained worldwide attention since they offer a new cost-effective way to generate renewable and green energy. In the current work, the structural, electrical, elastic, optical and thermoelectric properties of new perovskites CsInZrX6 (I, Cl and Br) were explored by density-functional theory (DFT). The results indicated that the computed lattice parameters agree really well with the current experimental and theoretical results. Moreover, the band structure profile strongly suggests that the compounds exhibit a semiconducting nature with a direct band gap. The analysis of their optical properties reveals that the perovskites possess a low reflectivity (below 23%) and a high optical absorption coefficient (106 cm−1). This is also supported by the evaluation of their calculated elastic constants and their related parameters in cubic structure which show that these compounds are brittle, mechanically stable and possess covalent bonds. On the other hand, in addition to exhibiting outstanding optoelectronic and mechanical characteristics, CsInZrCl6 also possesses dynamical stability, making it a promising candidate for application in various optoelectronic devices except for solar cells due to its relatively large bandgap. Furthermore, the BoltzTraP software was used to compute the materials’ thermoelectric properties, with the computed values of the figure of merit (ZT) for CsInZrBr6, CsInZrCl6 and CsInZrI6 being 0.76, 0.73 and 0.725, respectively. This is also a strong indication that these materials are potential for thermoelectric applications.

Combined X-ray Diffraction Analysis and Quantum Chemical Interpretation of the Effect of Thermal Neutrons on the Geometry and Electronic Properties of CdTe

Objective: Substantiation of the result of the interaction of thermal neutrons with CdTe crystals by quantum-chemical methods and comparison of the experimental results with the results of quantum-chemical calculations. Methods: Single crystal samples of cadmium telluride (CdTe) were obtained by a modified Bridgman method. The plates cut from the single crystal were subjected to mechanical grinding with abrasive paper of the type P1,200-P4,000, mechanical polishing with silver paste. To clean the surface of the plate from contamination, it was washed in ethyl alcohol. In the experimental part of the work, the influence of low thermal neutron fluxes on the structural parameters of CdTe was studied. The samples were irradiated with a thermal neutron flux in the range from 2.64×107 neutron/cm2 to 1.85×109 neutron/cm2. To study the structure of CdTe crystals, the method of X-ray structural analysis was used, using a DRON-3 X-ray diffractometer. In the second part of the work, computer modeling of the process of interaction of thermal neutrons on CdTe crystals was carried out. Results: X-ray diffraction analysis of the crystals showed that as a result of irradiation with low thermal neutron fluxes, the structural parameters of CdTe improve, as evidenced by the ordering of the crystallites. In addition, in this region of the thermal neutron flux the resistance of the crystals decreases. Conclusion: Calculations of the crystal lattice parameters of CdTe are in good agreement with experimental data. The electronic and optical properties of CdTe have been studied. A decrease in the band gap after irradiation with thermal neutrons has been shown.

D and Ds decay constants in Nf = 2 + 1 QCD with Wilson fermions

We present results for the leptonic decay constants of the D and Ds mesons from Nf = 2 + 1 lattice QCD. We employ a set of 49 high statistics gauge ensembles generated by the Coordinated Lattice Simulations (CLS) effort utilising non-perturbatively improved Wilson fermions and the tree-level Symanzik improved gauge action at six values of the lattice spacing in the range a = 0.098 fm down to a = 0.039 fm, with pion masses varying from around 420 MeV down to below the physical point. The ensembles lie on three trajectories in the quark mass plane, two trajectories intersecting close to the physical quark mass point and the third one approaching the SU(3) chiral limit, enabling tight control of the light and strange quark mass dependence. We obtain fDs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {f}_{{\ extrm{D}}_{\ extrm{s}}} $$\\end{document} = 246.8(1.3) MeV, fD = 208.4(1.5) MeV and fDs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {f}_{{\ extrm{D}}_{\ extrm{s}}} $$\\end{document}/fD = 1.1842(36), where the precision of our results is mostly limited by the determination of the scale.