Lattice Parameters Research Articles

Universality in the Structure and Dynamics of Water under Lipidic Mesophase Soft Nanoconfinement.

Water under soft nanoconfinement features physical and chemical properties fundamentally different from bulk water; yet, the multitude and specificity of confining systems and geometries mask any of its potentially universal traits. Here, we advance in this quest by resorting to lipidic mesophases as an ideal nanoconfinement system, allowing inspecting the behavior of water under systematic changes in the topological and geometrical properties of the confining medium, without altering the chemical nature of the interfaces. By combining Terahertz absorption spectroscopy experiments and molecular dynamics simulations, we unveil the presence of universal laws governing the physics of nanoconfined water, recapitulating the data collected at varying levels of hydration and nanoconfinement topologies. This geometry-independent universality is evidenced by the existence of master curves characterizing both the structure and dynamics of simulated water as a function of the distance from the lipid-water interface. Based on our theoretical findings, we predict a parameter-free law describing the amount of interfacial water against the structural dimension of the system (i.e., the lattice parameter), which captures both the experimental and numerical results within the same curve, without any fitting. Our results offer insight into the fundamental physics of water under soft nanoconfinement and provide a practical tool for accurately estimating the amount of nonbulk water based on structural experimental data.

Preferred crystal plane electrodeposition of aluminum anode with high lattice-matching for long-life aluminum batteries

Aluminum batteries have become the most attractive next-generation energy storage battery due to their advantages of high safety, high abundance, and low cost. However, the dendrite problem associated with inhomogeneous electrodeposition during cycling leads to low Coulombic efficiency and rapid short-circuit failure of the aluminum metal anode, which severely hampers the cycling stability of aluminum battery. Here we show an aluminum anode material that achieves high lattice matching between the substrate and the deposit, allowing the aluminum deposits to maintain preferred crystal plane growth on the substrate surface. It not only reduces the nucleation barrier of aluminum and decreases electrode polarization, but also enables uniform deposition of aluminum, improving the cycling stability of aluminum batteries. Aluminum anode with (111) preferred crystal plane can stably 25000 cycles at the current density of 5 A·g−1, with a capacity retention rate of over 80%.

Strain-dependence of Te interstitial diffusion in CdTe

While the dominant defects which control non-radiative recombination and long-range interstitial diffusion in CdTe correspond to Cd vacancies and Te anti-sites, the short-range diffusion of Te and Se interstitials between these defects is also of interest, since they both play a role in defect passivation. In addition, since CdTe thin films are typically polycrystalline and may also involve interfaces with materials with different lattice constants, the effects of strain are also of interest. Here we present the results of molecular dynamics (MD) simulations of Te interstitial diffusion in zincblende CdTe for values of the triaxial strain ranging from −2% (compressive) strain to +2.8% (tensile) strain. By carrying out MD simulations of Te interstitial diffusion over a range of temperatures, and then carrying out Arrhenius fits, we have determined the effective activation barrier Ea and prefactor D 0 for each value of the global strain. We find that both Ea and D 0 exhibit non-monotonic behavior, increasing with both compressive and tensile strain. We also present an analysis of the key diffusion pathways for 3 different values of the strain which explains the non-monotonic strain dependence obtained in our simulations. Our results also indicate that in each case, the diffusion of interstitial Te involves a variety of concerted events with a wide range of activation barriers.

Unveiling the structural and optoelectronic properties of (P, Bi, Sb)-doped GaAs by first- principles calculations

In this work, we investigate the influence of M substitutions (M = P, Bi, and Sb) on the structural, electronic, and optical properties of gallium arsenide, GaM x As1-x for x=0,0.25,0.50,0.75,1.0 using density functional theory (DFT). We have observed that the cubic symmetry of the semiconductors in conserved, and lattice constants show a linear behavior with dopant concentration, according to Vegard’s law. Specifically, the lattice constants increased for Bi and Sb dopants, whilst decreased for P dopants. Furthermore, the bulk modulus decreased with an increase in M-concentration for all M-doped systems. The energy analysis showed that the P-doped system was the most stable system. In terms of the electronic band structure, all M-doped compounds exhibited a direct electronic band gap. The P-doped system showed a wide band gap, while the Sb-doped systems displayed a narrow band gap, both compared to pristine GaAs. The Bi-doped system showed metallic-like behavior. To gain insights into the linear optical properties of the GaM x As1-x compounds, we calculated the real and imaginary parts of the dielectric function, as well as other optical parameters such as the absorption coefficient, refractive index, extinction coefficient, and reflectivity. The results showed that P doping leads to a blue-shift in the optical absorption coefficient, while Bi and Sb doping lead to a red-shift. These findings provide valuable theoretical insights for the potential application of GaM x As1-x semiconductors in photovoltaics and optoelectronic devices.

Narrowing Band Gap of Zno Codoping (Al+Mn) as a Photocatalyst Candidate for Degraded Textile Dye Wastewater

Photocatalyst degradation is one method to reduce industrial textile dye pollution in water. In this study, ZnO material has been synthesized by codoping Al and Mn by chemical coprecipitation method to determine the structural properties and optical properties of the material. From this research, it was found that the structure of ZnO after codoping Al and Mn did not change the hexagonal wurtzite phase but changes in other lattice parameters. The addition of Mn and Al codoping is reported to affect the intensity of XRD peaks, especially on the 101 lattice. The higher the scattering peak, the more angular the shift, indicating the magnitude of oxygen vacancies. The reflectance confirms this result that increasing Mn concentration decreases the energy gap to 3.258 eV. From these structural properties and energy gap values, ZnO codoping Al and Mn materials can be included in candidate materials that can be used as photodegradation agents for textile dyes.

Ultraviolet active novel chalcogenides AScSe2 (A= K, Cs): The structural, optoelectronic, mechanical, vibrational, and thermodynamical properties for energy harvesting applications

It is essential nowadays to investigate some unique and appropriate materials for optoelectronic applications. We deliberate here for the first time, the structural, optoelectronic, mechanical, vibrational, and thermodynamical properties of hexagonal structured selenium-based ternary chalcogenides AScSe2 (A = K, Cs) by using Perdew-Burke-Ernzerhof Generalized-Gradient-Approximation (PBE-GGA). The lattice angles for these materials are found as α = β = 90° and γ = 120°. KScSe2 is optimized with lattice parameters a = b = 4.3 (Å), c = 7.81 (Å) whereas, CsScSe2 is relaxed at a = b = 4.43 (Å) and c = 8.51 (Å). The hybrid Heyd-Scuseria-Ernzerhof (HSE06) functional overestimates the lattice parameters to the extent that for KScSe2 these are found as a = b = 4.92 (Å), c = 7.10 (Å) and for CsScSe2 a = b = 5.15 (Å), c = 7.09 (Å). The energy band gap confirms the semiconducting nature of these materials. Born's criteria endorses the mechanical stability of these materials. Moreover, the temperature dependence of thermodynamic potentials and specific heat at constant volume is also determined using the harmonic approximation. The negative value of free energy ensures their thermodynamical stability. The vibrational modes are calculated by plotting the phonon dispersion and the vibrational density of states (VDOS) where infrared (IR) and Raman spectroscopy are used to characterize the vibrational modes. The optical parameters are examined at a smearing value of 0.5 eV that portray good absorptivity of the incident light from the Ultraviolet (UV) region. Thus, these materials may be potential ones to be utilized for energy harvesting applications via photovoltaic.

Deep learning of plausible bandgaps in dispersion curves of phononic crystals

Abstract Phononic crystals represent an interesting class of metamaterials that can be utilized to regulate or manipulate vibration, sound propagation, and thermal transport. Their useful features mainly arise from the bandgaps in their dispersion curves, preventing the passage of waves within specific frequency ranges. However, it is often costly and time-consuming to obtain the dispersion curves, and the reverse engineering of phononic crystals to have pre-defined bandgaps possesses even greater challenges. In this research, we address this issue by employing a deep artificial neural network to predict the bandgap ratio and the characteristics of plausible bandgaps, focusing on the localized resonance in columnar phononic crystals. We utilized two geometric parameters, i. e. the ratio of diameter and height of the cylindrical resonators relative to the lattice constant, achieving a determination coefficient of 0.9993 for predicting the characteristics of the bandgaps and 0.9827 for predicting the bandgap ratio. To verify the model and better understand its behavior, we introduce Shapley values. These values provide a comprehensive insight into how each geometric parameter influences the predicted bandgap ratios.

Exact lattice chiral symmetry in 2D gauge theory

We construct symmetry-preserving lattice regularizations of 2D QED with one and two flavors of Dirac fermions, as well as the “3450” chiral gauge theory, by leveraging bosonization and recently proposed modifications of Villain-type lattice actions. The internal global symmetries act just as locally on the lattice as they do in the continuum, the anomalies are reproduced at finite lattice spacing, and in each case we find a sign-problem-free dual formulation. Published by the American Physical Society 2024

Study of the stoichiometry effect on the structure and loss kinetics of photogenerated current carriers in Cu2-δBaSnS4 (0≤δ≤0.4) quaternary copper compounds

The solid-phase method was applied to synthesize Cu2-δ BaSnS4 (0≤δ ≤ 0.4) polycrystalline powders. The lattice parameters were refined. It was shown that the crystal structure parameters changed. For the first time, Raman spectra were experimentally obtained for copper-deficient samples. It was found that some difference in the position of major peaks is due to the Cu2-δBaSnS4 structure changing with increasing δ, as well as a partial valence change in tin or copper atoms. Using X-ray photoelectron spectroscopy, it was shown that when going from Cu2BaSnS4 to Cu1.6BaSnS4, there was no change in the valence state of copper, but the valence state of tin particularly changed. The lifetimes of the current carriers in the synthesized samples were significantly less than 10 ns.

Strain aided drastic reduction in lattice thermal conductivity and improved thermoelectric properties in Janus MXenes.

Surface and strain engineering are among the cheaper ways to modulate structure property relations in materials. Due to their compositional flexibilities, MXenes, the family of two-dimensional materials, provide enough opportunity for surface engineering. In this work, we have explored the possibility of improving thermoelectric efficiency of MXenes through these routes. The Janus MXenes obtained by modifications of the transition metal constituents and the functional groups passivating their surfaces are considered as surface engineered materials on which bi-axial strain is applied in a systematic way. We find that in the three Janus compounds Zr2COS, ZrHfO2and ZrHfCOS, tensile strain modifies the electronic and lattice thermoelectric parameters such that the thermoelectric efficiency can be maximised. A remarkable reduction in the lattice thermal conductivity due to increased anharmonicity and an elevation in Seebeck coefficient are obtained by application of moderate tensile strain. With the help of first-principles electronic structure method and semi-classical Boltzmann transport theory we analyse the interplay of structural parameters, electronic and dynamical properties to understand the effects of strain and surface modifications on thermoelectric properties of these systems. Our detailed calculations and in depth analysis lead not only to the microscopic understanding of the influences of surface and strain engineering in these three systems, but also provide enough insights for adopting this approach and improve thermoelectric efficiencies in similar systems.

First-principles study of non-linear thermal expansion in cadmium titanate by molecular dynamics incorporating nuclear quantum effects.

First-principles molecular dynamics (FPMD) simulations were applied for analyzing structural evolutions around the paraelectric-ferroelectric phase transition temperature in the perovskite-type cadmium titanate, CdTiO3. Since the phase transition is reported to occur at the low temperature around 80 K, the quantum thermal bath (QTB) method was utilized in this study, which incorporates the nuclear quantum effects (NQEs). The structural evolutions in the QTB-FPMD simulations are in reasonable agreement with the experimental results, by contrast in the conventional FPMD simulations using the classical thermal bath (CTB-FPMD). Especially, the non-linear thermal expansion of lattice constants around the phase transition temperature was well reproduced in the QTB-FPMD with the NQEs. Thus, the NQEs are of importance in phase transitions at low temperatures, particularly below the room temperature, and the QTB is useful in that it incorporates the NQEs in MD simulations with low computational costs comparable to the conventional CTB.

Full Picture of Lattice Deformation in a Ge1 - xSnx Micro-Disk by 5D X-ray Diffraction Microscopy.

Lattice strain in crystals can be exploited to effectively tune their physical properties. In microscopic structures, experimental access to the full strain tensor with spatial resolution at the (sub-)micrometer scale is at the same time very interesting and challenging. In this work, how scanning X-ray diffraction microscopy, an emerging model-free method based on synchrotron radiation, can shed light on the complex, anisotropic deformation landscape within three dimensional (3D) microstructures is shown. This technique allows the reconstruction of all lattice parameters within any type of crystal with submicron spatial resolution and requires no sample preparation. Consequently, the local state of deformation can be fully quantified. Exploiting this capability, all components of the strain tensor in a suspended, strained Ge1 - xSnx /Ge microdisk are mapped. Subtle elastic deformations are unambiguously correlated with structural defects, 3D microstructure geometry, and chemical variations, as verified by comparison with complementary electron microscopy and finite element simulations. The methodology described here is applicable to a wide range of fields, from bioengineering to metallurgy and semiconductor research.

Extension of the lattice-based aggregation-volume-bias Monte Carlo approach to molecular crystals: Quantitative calculations on the thermodynamic stability of the urea polymorphs.

Motivated by the recent success in using a latticed-based version of the aggregation-volume-bias Monte Carlo method to determine the thermodynamic stabilities of both bcc and fcc clusters formed by Lennard-Jones particles, this approach is extended to the calculation of the nucleation-free energies of solid clusters formed by urea at 300K in two different polymorphs, i.e., form I and form IV. In addition to the lattice confinement, the constraint on the molecular orientation was found necessary to ensure that the clusters sampled in these simulations are in the corresponding form. A model that can reproduce the experimental properties such as density and lattice parameters of form I at ambient conditions is used in this study. From the size dependencies of the free energies obtained for a finite set of clusters studied, the free energies of clusters at other sizes, including an infinitely large cluster, were extrapolated. At the infinite size, equivalent to a bulk solid, form I was found to be more stable than form IV, which agrees with the experimental results. In addition, form I was found to be thermodynamically stable throughout the entire cluster size range investigated here, which contradicts the previous finding that small form I clusters are unstable from the crystal nucleation simulation studies.

Coal-derived boron and phosphorus co-doped activated carbon with expanded interlayer space for high performance sodium ion capacitor anode

Aiming at the key problem of Na+ insertion difficulty and low charge transfer efficiency of activated carbon materials. It is an effective strategy to increase the lattice spacing and defect concentration by doping to reduce the ion diffusion resistance and improve the kinetics. Hence, anthracitic coal is used to prepare activated carbon (AC) and B,P-doped activated carbon (B,P-AC) as the cathode and anode materials for high-performance all-carbon SICs, respectively. AC cathode material has high specific surface area and reasonable micropore structure, which shows excellent capacitance performance. B,P-AC anode material has the advantages of extremely high specific surface area (1856.1 m2/g), expanded interlayer spacing (0.40 nm) and uniform distribution of B and P heteroatoms. Hence, B,P-AC anode achieves a highly reversible Na+ storage capacity of 243 mAh/g at a current density of 0.05 A/g. Density functional theory (DFT) calculations further verify that B,P-AC has stronger Na+ storage performance. The final assembled B,P-AC//AC SIC offers a high energy density of 109.78 Wh kg−1 and a high-power density of 10.03 kW kg−1. The high-performance coal-derived activated carbon of this work provides a variety of options for industrial production of electrode materials for sodium ion capacitors.

Prediction of the structural and magnetic properties of the all-d-metal Heusler alloys Ni–Mn–Cr

In this work, all-d metal Heusler alloys Ni–Mn–Cr were predicted by first principles. Their structure, magnetism, tetragonal distortion and electronic properties were studied. The cubic groud state structures of Ni2MnCr and NiMnCr2 are XA type, and that of NiMn2Cr is L21 type. All of them have magnetism. The change of their lattice constants is closely related to the covalent radius of atoms. Ni2MnCr has a stable tetragonal phase and may undergo martensitic transition. NiMn2Cr has a lower energy tetragonal phase, but is dynamically unstable. The equilibrium volumes of the two compounds expand through tetragonal distortion. NiMnCr2 does not have a lower energy tetragonal phase. In the tetragonal distortion, the atomic magnetic moments are influnced by the interatomic distance and the magnetic moments of neighboring atoms. The origin of the tetragonal distortion and magnetic properties was discussed in terms of the electronic density of states.

Genetic-algorithm-combined density functional theory calculations for investigating atomic properties of Si−Ge alloys

Compound semiconductors are expected to expand the possibilities of semiconductor applications. In particular, Ⅳ−Ⅳ compound semiconductors, such as silicon−germanium (Si−Ge) alloys, have received much attention over the past several decades. Although many scholars have conducted experiments on Si−Ge alloys, few scholars have conducted theoretical simulations on them. Thus, fundamental understanding of nanoscale phenomena in the Si−Ge alloys is still insufficient. To address this problem, we identified energetically stable structures of the Si−Ge alloys using density-functional-theory (DFT) first-principles calculations and genetic algorithm (GA) and evaluated various properties of the Si−Ge alloys. We confirmed that the formation energies of the stable structures identified by GA-combined DFT calculations were lower than those of other Si−Ge alloys registered in an existing crystal structure database. The lattice constants and electronic band gaps of these stable structures were evaluated using DFT calculations, and trends in their properties similar to those reported in previous experimental studies were verified. From the evaluation of coordination number according to the Boltzmann distribution, we found that homoelement bonds (Si–Si and Ge−Ge) are easier to form than heteroelement bonds (Si−Ge) in the stable structures of Si−Ge alloys at any composition.

Structural and optical properties of green-synthesised tricobalt tetroxide nanoparticles

In this study, we investigated the structural and optical properties of garlic extract-based green-synthesised tricobalt tetroxide nanoparticles. Transmission electron microscopy revealed a particle size range of 8–22 nm for the prepared powder sample. Powder x-ray diffraction data and Rietveld refinement results confirmed the spinel cubic crystal structure of the tricobalt tetroxide nanoparticles, with an average crystallite size of 11.23 nm. This crystal structure corresponds to the Fd3̅m space group and has an average lattice constant of 0.791 nm. The bond lengths of Co3+–O2− and Co2+–O2− are measured to be 0.188 nm and 0.190 nm, respectively. The FTIR data provided evidence of the presence of various functional bands, which helped qualitatively determine the purity of the sample. The UV–vis spectrum estimated two direct energy band gap values (3.7 eV and 2.2 eV) that may be useful for efficient interaction with a wide range of ray spectra to create more electron–hole pairs for various photo-responsive applications, such as dye degradation, solar cells, and optoelectronic components.

SYNTHESIS AND CHARACTERIZATION OF MAGNETITE NANOMATERIALS IN TIANYAR IRON SAND USING CO-PRECIPITATION METHOD

In the current era of scientific and technological progress, nanomaterials have emerged as a deeply fascinating and significant field of research. This paper presents a case study on the synthesis and characterization of Fe₃O₄ nanomaterials derived from the iron sand of the Tianyar, utilizing the co-precipitation method with modifications made to the pH values during synthesis. The research encompasses three primary stages: extraction of iron sand, synthesis of Fe3O4 nanomaterials, and subsequent characterization of these nanomaterials. The iron sand extraction phase involved passing it through a permanent magnet ten times to remove impurities. Subsequent synthesis produced a dark black magnetite nanomaterial powder displaying magnetic properties, rendering it responsive to magnet attraction. Analysis of these nanomaterials using X-ray diffraction (XRD) unveiled discernible peaks in the diffraction pattern, suggesting that the magnetite nanomaterials possess a cubic crystal structure. The size of the Fe3O4 nanomaterials decreases as the pH of precipitation increases, with respective sizes of approximately 18.00 nm for pH 9, 14.69 nm for pH 10, and around 13.68 nm for pH 11, as determined using Scherrer’s formula. The lattice parameters observed for samples synthesized at pH 9, 10, and 11 are sequentially measured as a = 8.59 Å, 8.81 Å, and 8.80 Å. Analysis using SEM-EDS revealed that the sample morphology appears rough, with evidence of particle agglomeration leading to uneven particle distribution. There are additional trace elements present, including C, Al, S, Ti, and Cl, albeit in smaller quantities. Nevertheless, the primary elements crucial for forming Fe3O4 nanomaterials, namely Fe and O, exhibit the highest percentages in composition analysis.

Microstructural analysis and densification of ordinary Portland cement mortars incorporated with minimal nano-TiO2: intermixing and surface coating on both fresh and hardened surfaces

The present study investigated the microstructural properties of ordinary Portland cement (OPC)-modified with minimum dosage of nano TiO2 on fresh and hardened cement mortar surfaces and intermixed samples. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used to analyze the morphology and hydration products of the OPC specimens doped with nanotitanium (NT).Additionally, XRD coupled with Rietveld refinement was employed to quantify the crystal phases and refine the crystal structure model through the comparison of the calculated diffraction pattern to the measured pattern. Subsequently, crystallographic analysis was conducted to evaluate the crystallographic structure and to confirm the existence of specific atoms and bonds within the crystal structure altered with NT. The findings revealed that the addition of minimal NT resulted in a more compact and denser microstructure, characterized by increased formation of calcium silicate hydrate (CSH) gel and a reduction in calcium hydroxide (CH) crystals.This led to a reduction in the porosity of the hardened coating surface, with similar improvements observed for the fresh coating and intermixed samples compared to those of the control mortar. A decrease in the lattice parameters, accompanied by an increase in the number of atoms, bonds and polyhedra in the crystal structure, led to alterations in the interatomic spacing and contributed to the densification of the cementitious matrix.The findings also showed that NT integration led to a more compact structure with shorter bond distances and smaller polyhedral volumes for the Ti samples than for the control sample. Moreover, compared with the freshly cast and hardened coating samples, the NT-intermixed samples exhibited the shortest Ti–O bond distances and the smallest polyhedral volume. Overall, the analysis presented in this study significantly contributes to the development of novel and environmentally friendly photocatalytic cementitious materials at minimal dosages.

Revision of JIS R7651: “Measurement of lattice constants and crystallite sizes of carbon materials”

Revision of JIS R7651: “Measurement of lattice constants and crystallite sizes of carbon materials”