Structural Properties Research Articles

A rotation total variation regularization for full waveform inversion

Abstract Mathematically, full waveform inversion is a nonlinear and ill-posed inverse problem, requiring a regularization method to obtain a reasonable result. Total variation regularization is an effective regularization method which can preserve the sharp edges of the solution. It is well-known that the standard total variation regularization usually leads to stair-casing artifacts in slanted structures. Thus, the standard total variation regularization may not be effective in solving the full waveform inverse problem, due to the slanted properties of the subsurface structures. In this paper, we propose a rotational total variation regularization method based on the weighting rotational transform operator and the standard total variation regularization for the full waveform inverse problem. To further improve the resolution of the inverted results for different directional structures, a hybrid regularization method combining the rotational and standard total variation regularization is proposed. An efficient version of the conjugate gradient method, i.e., CGOPT, is used to efficiently solve the proposed methods. Numerical experiments based on Sigsbee and Marmousi2 models are carried out to demonstrate the effectiveness of our methods.

Numerical Simulation and Evaluation of Y\(_2\)S\(_3\) and Y\(_2\)TeS\(_2\) on Structural, Stability, and Electronic Properties for Photocatalytic Water Splitting Applications

We attempt to establish a computational insight into the structural, mechanical, dynamic, electronic, and photocatalytic properties of orthorhombic phase Yttrium sulphide Y\(_2\)S\(_3\) and Y\(_2\)TeS\(_2\) Janus compounds by density functional calculations. The Janus Y\(_2\)TeS\(_2\) is a hypothetical compound with all properties computed forthe first time. Computed lattice parameters for Y\(_2\)S\(_3\) are in reasonable agreement with available experimental data. Mechanical properties are investigated by calculating the elastic constant to check for Born stability criteria. A finite displacement vibrational frequency study confirmed that Y\(_2\)S\(_3\) and Y\(_2\)TeS\(_2\) are stable; negative phonon frequencies were checked. Computed PBEsol and MBJ band structures found that Y\(_2\)S\(_3\) is a direct band gap semiconductor, while Y\(_2\)TeS\(_2\) is an indirect band gap semiconductor. Band gaps estimated from the HSE06 hybrid functional are 2.75 eV and 2.70 eV for Y2S2 and Y\(_2\)TeS\(_2\), respectively, suggesting that they are semiconductor materials with wide band gaps that can absorb light in the ultraviolet region. Mullikan’s electronegativity screen technique, used to calculate valence band maximum VBM and conduction band minimum CBM potentials, predicted that Y2S3 and Y\(_2\)TeS\(_2\) have suitable conduction band minimum potential of -1.05 V and -1.30 V and valence band maximum of 1.70 V and 1.40 V, respectively, versus normal hydrogen electrode (NHE) at PH = 0 to trigger the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) simultaneously.

Understanding the impact of plasma functionalized MWCNTs on the structure, physicochemical and mechanical properties of PEMA

In this study, plasma functionalized multiwalled carbon nanotubes, f-MWCNTs, were incorporated into a poly(ethyl methacrylate), PEMA, polymer matrix at different wt.% (0.005, 0.01, and 0.02 wt.%) to prepare nanocomposite films using the traditional solution casting method. The XRD, Raman spectroscopy, XPS, TGA, mechanical analysis and UV–Vis spectroscopy techniques were employed to investigate the effects of the wt.% of f-MWCNTs on the structure, spectroscopic and other physiochemical properties of the synthesized films. XRD analysis showed a monotonic change in the PEMA structure upon incorporation of f-MWCNTs at different wt.%. The XPS results showed an increase of oxygen-based functional groups C-O and O-C-O on the PEMA/f-MWCNTs/ composite films compared to pure PEMA. Raman spectroscopy results consistent with the XRD and XPS findings, confirming the homogeneous distribution of f-MWCNTs in the PEMA matrix. Thermal stability of f-MWCNTs/PEMA improved as the f-MWCNTs content increased. Optical studies showed a reduction in the bandgap energy as the f-MWCNTs content increased, accompanied by significant improvements in optical properties such as refractive index (n), extinction coefficient (k), dielectric constants (ε′ and ε″), and optical conductivity (σopt). Mechanical testing revealed enhancements in breaking strength, Young’s modulus, yield stress, and elongation at break with increasing f-MWCNTs concentrations. Furthermore, the AC electrical conductivity of the films also improved, demonstrating better charge transport capabilities. These synergistic enhancements in optical, thermal, mechanical, and electrical properties make PEMA/f-MWCNTs nanocomposites promising candidates for advanced applications, including optoelectronic devices, optical components, and conductive packaging materials.

Changes in morphofunctional parameters of erythrocytes and oxygen-binding capacity of hemoglobin under the influence of microorganisms of various types.

When bacteria interact with red blood cells, the plasma membrane receives signals from the microorganism adhesins, and the functional work of the erythrocyte as a whole depends on the biomembrane phospholipid condition. However, the microorganism effect on the structural and functional properties of the red blood cell membrane, as well as on the hemoglobin oxygen-binding ability has not been studied enough. Given the foregoing, we sought to study these issues in our work. The study used the "bacteria-red blood cells" model, using archival microbial strains (Staphylococcus aureus, Escherichia coli, Mycolicibacterium rutilum, and M. iranicum) and donor erythrocytes. The structural and functional properties of the red blood cell membrane phospholipids and the spectral characteristics of the hemoglobin molecule were studied using Raman spectroscopy. To study changes in red blood cell (RBC) morphology under the impact of microorganisms, laser interference microscopy was used. The results show that various types of microorganisms affected the conformational structure of the RBCs membrane phospholipid bonds, which contributed to changes in the morphological characteristics of cells, resulting in functional changes in both the red blood cell as a whole and the main RBC oxygen transport protein-hemoglobin.

Single Molecule Junction of Polynuclear Alkynylplatinum-Based Organometallic Molecular Wires: A Theoretical Study of the Long-Range Transport Effect of Linkage to Gold Surfaces.

Density functional theory (DFT) and nonequilibrium Green's function (NEGF) calculations were employed to elucidate the single-molecule conductance properties of a series of polynuclear alkynylplatinum-based organometallic wires, AcS[[(p-tol3P)2PtC≡C-C≡C-C≡C-C≡C]mPt(Pp-tol3)2SAc (m = 1-3), featuring platinum centers incorporated within polyyne chains. This investigation aimed to determine the influence of the embedded platinum centers on conductance compared to all-carbon polyynes and organometallic wires with terminal metal entities. While the structural and electronic properties of the individual molecular units are minimally affected by the chain extension, DFT-NEGF calculations on the corresponding Au-wire-Au junctions reveal an exponential decay in conductance with increasing molecular length, consistent with a tunneling-dominated transport mechanism. However, for longer wires (m = 3), the markedly low conductance and partial localization of frontier orbitals indicate that hopping transport could contribute to the overall transport mechanism. These findings provide valuable insights into the factors governing charge transport, including the interplay of length, platinum incorporation, and orbital localization in polynuclear alkynylplatinum-based organometallic wires, which may have implications for the future design of molecular wires.

Self-driving lab for the photochemical synthesis of plasmonic nanoparticles with targeted structural and optical properties

Many applications of plasmonic nanoparticles require precise control of their optical properties that are governed by nanoparticle dimensions, shape, morphology and composition. Finding reaction conditions for the synthesis of nanoparticles with targeted characteristics is a time-consuming and resource-intensive trial-and-error process, however closed-loop nanoparticle synthesis enables the accelerated exploration of large chemical spaces without human intervention. Here, we introduce the Autonomous Fluidic Identification and Optimization Nanochemistry (AFION) self-driving lab that integrates a microfluidic reactor, in-flow spectroscopic nanoparticle characterization, and machine learning for the exploration and optimization of the multidimensional chemical space for the photochemical synthesis of plasmonic nanoparticles. By targeting spectroscopic nanoparticle properties, the AFION lab identifies reaction conditions for the synthesis of different types of nanoparticles with designated shapes, morphologies, and compositions. Data analysis provides insight into the role of reaction conditions for the synthesis of the targeted nanoparticle type. This work shows that the AFION lab is an effective exploration platform for on-demand synthesis of plasmonic nanoparticles.

Hydrostatic Pressure-Driven Insights into Structural, Electronic, Optical, and Mechanical Properties of A3PCl3 (A = Sr, Ba) Cubic Perovskites for Advanced Solar Cell Applications

Hydrostatic Pressure-Driven Insights into Structural, Electronic, Optical, and Mechanical Properties of A3PCl3 (A = Sr, Ba) Cubic Perovskites for Advanced Solar Cell Applications

Photocatalytic degradation of organic dyes by synthesised lanthanum oxide nanoparticle

ABSTRACT Lanthanum oxide nanoparticles have gathered significant attention from researchers due to their exceptional free-radical scavenging properties. In this study, a lanthanum oxide was synthesised from the lanthanum nitrate via the sol-gel method using surfactant and characterised using various techniques such as UV-VIS, XRD and Zeta potential. The structural properties of the nanoparticles were analysed using XRD, DLS & ZETA potential techniques. The nanoparticles were subsequently used to evaluate their photocatalytic activity against Methylene blue (MB) and Malachite Green (MG) dye degradation, with experiments conducted under varying conditions, including pH, dye concentration, catalyst concentration, reaction temperature and different light sources (direct sunlight, UV-365 nm, and UV-254 nm). The degradation kinetics followed a pseudo-first-order kinetic model for MB and MG with rate constants 0.08842 min−1, 0.07852 min−1 respectively.

Fracture characteristics of slag-based geopolymer mortars with recycled aggregates under mode I and mode II Loading

This study investigates the fracture characteristics of slag-based geopolymer mortars (SGPM) incorporating recycled fine aggregates (RFA) from construction demolition waste. The research examines both tensile (mode I) and shear (mode II) fracture behaviors, analyzing the effects of different notch-to-depth ratios (0.20, 0.25, 0.30) and varying RFA replacement levels (10%, 20%, 30%, 40%). The experimental results reveal that increasing notch-to-depth ratios leads to increased brittleness, reducing fracture energy in both modes. Higher RFA levels further decrease overall strength and fracture energy, with a more significant impact on mode II. Mode II fracture energy is notably higher, approximately 23 times greater than mode I. The findings highlight the importance of balancing notch-to-depth ratios and RFA content to optimize SGPM’s mechanical performance for sustainable construction applications. This study concludes that while SGPM with RFA offers environmental benefits, careful consideration of RFA proportions and notch-to-depth ratios is crucial to maintain desired structural properties.

First-principles study on the physical properties of Al-based wide-bandgap perovskites Cs3AlIxBr6-x for optoelectronic applications

Abstract This study aims at exploring the potential of inorganic wide-bandgap mixed-halide aluminum-containing perovskites of Cs3AlIxBr6-x in solar harvesting, by investigating their structural, electronic, and optical properties with density functional theory (DFT) using the APW+lo method. The structural properties were calculated with the PBE-GGA potential. Volume optimization and negative formation energies confirm the structural and thermal stability of the compounds. The electronic and optical properties were calculated using TB-mBJ potential. The TB-mBJ corrected bandgaps revealed that these materials belong to the wide bandgap (WBG) perovskites family, displaying bandgaps in the range of 3-5 eV. The electronic properties confirmed their direct bandgap nature with I-p and Br-p states mainly contribute to the formation of VB, and the Al-s, Al-p, and Cs-d states to CB. Absorption coefficients range from 10-140 x 104 per cm in the UV region thus making these WBG perovskites suitable for applications in this region. Optical properties show the absorption of light beyond 3 eV and validate the calculated electronic bandgaps. Absorption coefficients, optical conductivity, and dielectric function (real and imaginary) were calculated and revealed a peak shift from higher to lower energies with increasing I concentration. The above results suggest that these materials can be highly considered for use in photovoltaics (PVs), optoelectronic devices (LEDs, PDs), to power small batteries in IoT, in agrivoltaics, and in fabrication of semi-transparent solar cells.

Water Is Cool: Advanced Phonon Dynamics in Ice Ih and Ice XI via Machine Learning Potentials and Quantum Nuclear Vibrations.

Low-dimensional water, despite the relative simplicity of its constituents, exhibits a vast range of phenomena that are of central importance in natural sciences. A large number of bulk as well as nanoscale polymorphs offer engineering possibilities for technological applications such as desalinization, drug delivery, or biological interfacing. However, little is known about the stability of such structures. Therefore, in this study, we employ an array of state-of-the-art computational techniques to study the vibrational properties of ice Ih and XI in their bulk and thin film forms in order to elucidate their structural stability and dynamic behavior. An efficient workflow, consisting of quantum mechanical simulations (based on density functional theory) and machine learning interatomic potentials (MTPs) coupled to temperature-dependent effective potentials (TDEP) and classical molecular dynamics, was verified necessary to capture the temperature-dependent stabilization of the phonons in bulk ice Ih and XI. Anharmonicity and nuclear quantum effects, incorporated in an efficient way through a quantum thermal bath technique, were found crucial to dynamically stabilize low-frequency lattice modes and high-frequency vibrational stretching involving hydrogen. We have identified three novel thin film structures that retain their stability up to at least 250 K and have shed light on their phonon characteristics. In addition, our examination of the Raman spectrum of ice underscores the shortcomings of predicting vibrational properties when relying entirely on the harmonic approximation or purely anharmonic effects. The corrected redistribution of vibrational intensities is found to be achieved only upon inclusion of quantum nuclear vibrations. This was found to be even more crucial for low-dimensional thin film (2D) structures. Overall, our findings demonstrate the significance of joining advanced computational methodologies in unraveling the intricate vibrational dynamics of crystalline ice materials, offering valuable insights into their thermodynamic and structural properties. Furthermore, we suggest a procedure based on MTPs coupled to a quantum thermal bath for the computationally efficient probing of nuclear effects in ice structures, although equally applicable to any other system.

Structural and electrical properties of CuO-doped NaNbO3 ceramics

Structural and electrical properties of CuO-doped NaNbO₃ ceramics

Correction: Theoretical Study of the Structural, Magnetic, Electronic and Elastic Properties of VSb-Based Half-Heusler Alloys

Correction: Theoretical Study of the Structural, Magnetic, Electronic and Elastic Properties of VSb-Based Half-Heusler Alloys

Solving Static and Dynamic Disorder in Cu4TiTe4: Crystal Structure and Thermodynamic Properties.

Cu4TiTe4 shows positional disorder because one of the copper atoms does not occupy a precise position in the unit cell. This fact complicates the development of simple and reliable crystalline models capable of capturing the promising thermodynamic and optical properties of Cu4TiTe4. Here, we select practical supercells accounting for the different Cu atomic environments in the crystal and identify nonequivalent structural configurations. Their electronic energies and thermodynamic properties are calculated by coupling DFT and the quasi-harmonic approximations. Average values corresponding to the experimentally observed Cu4TiTe4 structure are obtained introducing Boltzmann weights based on the total energy of these configurations. For Cu4TiTe4, differences in the calculated properties among the 16 nonequivalent configurations of its 2 × 2 × 1 supercell demonstrate the inadequacy of focusing just on a single configuration. After calculating the energy barriers associated with the diffusion of the disordered copper atoms among its four equivalent positions (lower than 0.5 eV), we evidence the importance of taking into account this dynamic disorder, which reveals a negative thermal expansion for this telluride at low temperatures, not found under the static disorder approach.

Hydrodynamic analysis of floating VLFS using multi-domain boundary element method

The present study emphasizes the investigation of rigid and flexible Very Large Floating Structures (VLFS) by analyzing the reflection and transmission coefficients, plate deflections and wave force on the floating structure. The study involves analyzing the hydrodynamic characteristics of a porous and rigid VLFS, and hydroelastic analysis of flexible VLFS. The analysis is performed using the coupled Multi-Domain Boundary Element Method (MDBEM) and Finite Difference Method (FDM) at finite water depth. The flexible VLFS is modelled based on the Euler–Bernoulli thin plate theory and the study is performed using small amplitude wave theory. The study evaluates the hydroelastic behaviour in terms of structural deflection and hydrodynamic parameters by varying the structural porosity. The reflection and transmission coefficients are analyzed to show the extent of wave propagation on the lee side and the seaside of the structure. The wave force coefficients obtained signify the importance of the structure's orientation for the oncoming waves. The numerical results are validated with the results available in the literature. The analysis is performed for different structural and material properties to obtain the minimal hydroelastic and hydrodynamic response to assess the optimum design criteria and suitability of the type of VLFS, thereby maintaining the stability of the structure for safer operations.

Mixed-Solvent-Induced Phase Separation Enables Anisotropy and Strengthening of Hydrogels Composed of Flexible Network Chains.

Achieving anisotropy in hydrogels is key to replicating the structural and mechanical properties of biological tissues. However, inducing anisotropy in hydrogel systems composed solely of flexible amorphous polymers is challenging, as these polymers typically exhibit thermally unstable anisotropic states, i.e., they are easy to disorient. In this study, a mixed-solvent-induced phase-separation approach to stabilize the orientation of such hydrogel networks after pre-stretching is introduced. Using polyacrylamide, a flexible polymer with a persistence length on the order of 10-1nm, as a model system, it is demonstrated that phase separation in a mixed solvent leads to the formation of dense and dilute polymer phases, with the dense phase effectively locking the anisotropy through robust inter- and intra-polymer interactions. A series of characterizations confirm that partial orientation can be preserved in the prestretched, phase-separated gel upon relaxation, resulting in significant mechanical enhancement along the orientation direction, including improvements in fracture stress, Young's modulus, and fracture toughness. The generality of this method, showing its effectiveness in other hydrogel systems and its adaptability to different solvent combinations is also validated. This work presents an unconventional strategy for preparing anisotropic hydrogels that typically struggle to maintain structural integrity.

The head-tail radio galaxy and revived fossil plasma in Abell 1775

Head-tail radio galaxies are characterized by a head, corresponding to an elliptical galaxy, and two radio jets sweeping back from the head, forming an extended structure behind the host galaxy that is moving through the intracluster medium (ICM). This morphology arises from the interaction between the diffuse radio-emitting plasma and the surrounding environment. Sometimes, in galaxy clusters, revived fossil plasma can be found, and it traces old active galactic nucleus ejecta with a very steep spectrum that has been re-energized through processes in the ICM, unrelated to the progenitor radio galaxy. We focus on the study of the central region of Abell 1775, a galaxy cluster in an unclear dynamical state at a redshift of z = 0.07203. It hosts two giant radio-loud elliptical galaxies, the head-tail radio galaxy that ‘breaks’ at the position of a cold front detected in the X-rays, filamentary revived fossil plasma, and central diffuse emission. This study aims to investigate and constrain the spectral properties and trends along the head-tail, as well as the revived fossil plasma, to better understand the formation process of the non-thermal phenomena in A1775. We make use of observations at three frequencies performed with LOFAR at 144 MHz, and new deep uGMRT observations at 400 MHz and at 650 MHz. We observe an overall steepening along the tail of the head-tail radio galaxy. In the radio colour-colour diagram, ageing models reproduce the emission of the head-tail. An unexpected brightness increase at the head of the tail suggests a complex bending of the jets. We derived the equipartition magnetic field and minimum pressure along the tail. We recovered the structure of the revived fossil plasma, which appears as thin filaments with ultra-steep spectra. We show that high-sensitivity, high-resolution observations at low frequencies are essential for detecting the full extent of the tail, enabling a deeper spectral analysis and resolving the structure and spectral properties of revived fossil plasma.

Analytical modeling of NH3 gas sensing using zigzag graphene nanoscrolls: energy band structure and electrical properties

Analytical modeling of NH3 gas sensing using zigzag graphene nanoscrolls: energy band structure and electrical properties

Panoramic analysis of 2D dirubidium telluride monolayer benchmarking the DFT approach

Through the DFT computations, the structural, vibrational, electronic, elastic, optical and thermal (thermoelectric, thermodynamic) properties of the two-dimensional Rb2Te monolayer are briefly contemplated. The Perdew-Bruke-Ernzerhof (PBE) form of generalized gradient approximation (GGA) functional in WIEN2k was deployed for the analysis of all these material properties. The trigonally crystallizing monolayer with an indirect band gap of 1.72 eV may be an upright single-layer that suffices distinct applications. ‘No negative’ phonon bands confirm the dynamical stability of the monolayer. The Rb2Te monolayer has large indirect band gap than Rb2S and Rb2Se. It exhibits mechanical stability with positive elastic constants satisfying the Born-Huang criterion for two-dimensional materials. The absorption coefficient spanning largely in the ultra-violet range makes the monolayer a congruous material for UV applications. Also, the thermoelectric figure of merit for p-type Rb2Te single-layer at room temperature is high (0.67) compared to the analogous series of compounds, that makes the monolayer a viable one for thermoelectric flexibility and experimental synthesis. The monolayer has high hole effective mass and D ratio. The obtained results aids in revealing the outstanding properties and excellent stability of the monolayer. Based on these findings the Rb2Te monolayer paves the way for promising applications in the fields of photovoltaics, thermoelectrics and UV-based applications.

Strain dependent properties of the Bi2Sr2CaCu2O8 superconductor: an ab initio study

Abstract Ab initio calculations were performed to investigate the effects of strain on the structural, electronic, and vibrational properties of the Bi2Sr2CaCu2O8 (Bi-2212) compound. To accurately represent the Bi-2212 ground state, a modulation correction was applied, generating a distorted structure with lower symmetry that better represents the incommensurate superstructure observed in this compound. Phonon spectra and electronic properties were calculated under various levels of c-axis strain, ranging from -2.0% to +2.0%. For the electronic properties, minor changes were observed in the electronic density of states and band structure. However, trends could be identified by analyzing the fine features of the band structure through a tight-binding model. The most significant changes were observed in the vibrational properties, where different trends emerged for the various Raman-active modes. The changes observed in the vibrational and electronic properties can be explained by examining the distances and overlap populations of the relevant bonds, as well as the reduced mass of certain modes. This work can serve as an input for analyzing experimental measurements, helping to distinguish structural effects from others.