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Heusler alloy has been widely utilized in magnetoresistive sensors to enhance the device performance. In this work, we theoretically investigate the performance of Heusler-alloy-based magnetoresistive sensors with a synthetic antiferromagnet (SAF) layer. The atomistic model combined with the spin accumulation model will be used in this work. The former is used to construct the reader stack and investigate the magnetization dynamics in the system. The latter is employed to describe the spin transport behavior at any position of the structure. We first perform simulations of the exchange bias (EB) phenomenon in the IrMn/ C o 2 F e S i (CFS) system providing a high EB field. Then, a realistic reader stack of IrMn/CFS/Ru/CFS/Ag/CFS is constructed via an atomistic model. Subsequently, the resistance–area product (RA) and magnetoresistance (MR) ratio of the reader can be calculated by using the spin accumulation model. As a result of the spin transport behavior in the Heusler-alloy-based reader stack including SAF structure at 0 K, an enhancement of the MR ratio up to 120 % and RA < 40 m Ω ⋅ μ m 2 can be observed. This study demonstrates the important role of the Heusler alloy and SAF layer in the development of magnetoresistive sensors for the application of readers in hard disk drives with an areal density beyond 2 Tb in−2. [ABSTRACT FROM AUTHOR]

Mesophase pitch (MPP)-based carbon fibers exhibit outstanding mechanical properties, notably an exceptionally high Young’s modulus. Despite extensive investigations into the microstructure of MPP-based carbon fibers, the influence of these factors on deformation mechanisms under tension remains unclear. This study employs the continuous defective graphene nanoribbons (dGNR) atomistic structure model for molecular dynamics simulations to explore the tensile failure mechanisms of MPP-based carbon fibers. In the simulation model, the structure of the defective region was generated through high-temperature annealing, and a transition region was introduced to prevent distortion and damage to the active graphene edges. The simulation reveals the evolutionary process of the microstructure of MPP-based carbon fibers under tension and achieves Young’s modulus predictions with greater accuracy than theoretical models. Additionally, the study shows that different strengths of interactions between adjacent graphene nanoribbons can lead to two distinct failure modes. Models with larger crystallite dimensions along the fiber axis and lower average defective concentrations exhibit geometric deformation coordination between adjacent nanoribbons, potentially elucidating the increasing strength trend in MPP-based carbon fibers with rising graphitization levels. Our simulations provide insights into the tensile failure mechanisms of MPP-based carbon fibers, offering valuable guidance for regulating their microstructure to enhance mechanical performance.

Vitreous silica is the most versatile material for scientific and commercial applications. Although large-scale atomistic models of vitreous-SiO2 (v-SiO2) having medium-range order (MRO) have been successfully developed by melt-quench through classical molecular dynamics, the MRO is not well studied for the smaller-scale models developed by melt-quench using ab-initio molecular dynamics (AIMD). In this study, we obtain atomistic models of v-SiO2 by performing melt-quench simulation using AIMD. The final structure is compared with the experimental data and some recent atomistic models, on the basis of the structural properties. Since AIMD allows for the estimation of electronic structure, a detailed study of electronic properties is also done. It shows the presence of defect states mainly due to dangling bonds in the band-gap region of electronic density of states, whereas the edge-shared type of defective structures in the glassy models are found to contribute mainly in the valence band. In addition, oxygen and silicon vacancies as well as bridging Oxygen type of defects were created and their contributions to the band-gap were studied. [ABSTRACT FROM AUTHOR]

Cylindrical ferromagnetic nanowires are of particular interest in nanomaterials science due to various manufacturing methods and a wide range of applications in nanotechnology, with special attention given to those with diameters less than the single domain limit. In the current study, the simulations of magnetic properties of isolated iron nanowires with a diameter of 5 nm and various aspect ratios, as well as two types of arrays of such nanowires (with hexagonal and square arrangement), were performed using atomistic spin model. In the case of a single nanowire, change of coercive field for different applied field directions with aspect ratio was discussed. It was shown that the evolution of the magnetization reversal mechanism from coherent rotation to domain wall propagation appears with increasing length of single nanowire. For the arrays of cylindrical nanostructures, it was revealed that different number of nearest neighbors for each nanostructure in square and hexagonal arrays have an influence on their magnetostatic interactions, which are the most significant for shortest interwire distances. The corresponding spin configurations during the remagnetization process showed the appearance of intermediate magnetization states (when a part of wires is magnetized parallel and part antiparallel to the field direction), connected with Barkhausen effect, which influence the observed hysteresis curves. [ABSTRACT FROM AUTHOR]

• Atomistic models of IPG are developed employing the melt-quench process using AIMD simulations. • IRO is successfully reproduced in the obtained IPG model. • FSDP in S(q) carries the structure connectivity information. • Dangling bonds majorly contribute to the defect states in DOS. • Q 1 units dominate in the obtained model. Iron Phosphate glass (IPG) has recently gained interest for immobilizing high level nuclear wastes. In the current study, we report the first atomistic model of IPG developed by performing ab-initio molecular dynamics (AIMD) simulations on crystalline Fe 3 (P 2 O 7) 2 following the melt-quench procedure. The resulting structure is characterized at short and intermediate length scales. Although it is quite challenging to reproduce the intermediate range order (IRO) in small-scale AIMD simulated models, from the analysis of ring size distribution and neutron structure factor, it is found that the obtained model successfully exhibits the IRO. Furthermore, the electronic density of states (DOS) of the system is plotted, and the band gap region denotes the presence of dangling bond defects. The effects of different vacancies in the DOS are also studied. Apart from this, elastic and vibrational properties are also studied, and the results are compared with the available theoretical and experimental results. [ABSTRACT FROM AUTHOR]

Cylindrical ferromagnetic nanowires are of particular interest in nanomaterials science due to various manufacturing methods and a wide range of applications in nanotechnology, with special attention given to those with diameters less than the single domain limit. In the current study, the simulations of magnetic properties of isolated iron nanowires with a diameter of 5 nm and various aspect ratios, as well as two types of arrays of such nanowires (with hexagonal and square arrangement), were performed using atomistic spin model. In the case of a single nanowire, change of coercive field for different applied field directions with aspect ratio was discussed. It was shown that the evolution of the magnetization reversal mechanism from coherent rotation to domain wall propagation appears with increasing length of single nanowire. For the arrays of cylindrical nanostructures, it was revealed that different number of nearest neighbors for each nanostructure in square and hexagonal arrays have an influence on their magnetostatic interactions, which are the most significant for shortest interwire distances. The corresponding spin configurations during the remagnetization process showed the appearance of intermediate magnetization states (when a part of wires is magnetized parallel and part antiparallel to the field direction), connected with Barkhausen effect, which influence the observed hysteresis curves.

Amyloid fibrils are associated with a number of neurodegenerative diseases, including fibrils of amyloid β42 peptide (Aβ42) in Alzheimer’s disease. These fibrils are a source of toxicity to neuronal cells through surface-catalyzed generation of toxic oligomers. Detailed knowledge of the fibril structure may thus facilitate therapeutic development. We use small-angle scattering to provide information on the fibril cross-section dimension and shape for Aβ42 fibrils prepared in aqueous phosphate buffer at pH = 7.4 and pH 8.0 under quiescent conditions at 37 °C from pure recombinant Aβ42 peptide. Fitting the data using a continuum model reveals an elliptical cross-section and a peptide mass-per-unit length compatible with two filaments of two monomers, four monomers per plane. To provide a more detailed atomistic model, the data were fitted using as a starting state a high-resolution structure of the two-monomer arrangement in filaments from solid-state NMR (Protein Data Bank ID 5kk3). First, a twofold symmetric model including residues 11 to 42 of two monomers in the filament was optimized in terms of twist angle and local packing using Rosetta. A two-filament model was then built and optimized through fitting to the scattering data allowing the two N-termini in each filament to take different conformations, with the same conformation in each of the two filaments. This provides an atomistic model of the fibril with twofold rotation symmetry around the fibril axis. Intriguingly, no polydispersity as regards the number of filaments was observed in our system over separate samples, suggesting that the two-filament arrangement represents a free energy minimum for the Aβ42 fibril. [ABSTRACT FROM AUTHOR]

We study the convergence of the elastic deformation from an atomistic model to a continuum model based on the Cauchy--Born rule for crystalline solids, where point defects are allowed to exist. We prove, under certain sharp stability conditions at zero temperature of the perfect lattice, that the solids are stable when the temperature and defect concentration are both low. Based on the stability conditions at zero/finite temperatures and with/without defects, we show that the defected version of the Cauchy--Born rule gives a correct nonlinear elasticity model in the sense that elastically deformed states of the atomistic model are closely approximated by solutions of the continuum model with free energy functionals obtained from the Cauchy--Born rule. Both static and dynamic problems are considered. The results are focused on the simple crystals and can be easily extended to complex ones. [ABSTRACT FROM AUTHOR]

Currently the multi-component diffusion kinetic databases, one of the key inputs for successful predictions of microstructural evolution, are by no means reliable since they are developed mostly by only seeking interdiffusion properties via diffusion-couple experiments but without considering the indispensable tracer or intrinsic diffusion coefficients. Estimating interdiffusion coefficients becomes challenging with the increasing number of components. In the present work, a mobility-extraction method is presented to directly determine atomic mobilities, which is in turn used to develop kinetic databases and then calculate all sorts of diffusion coefficients. It requires only one single-phase diffusion couple with Kirkendall markers to obtain the atomic mobilities in the marker position, with no limit on the number of components. This novel idea is realized on the basis of a new simulation scheme to solve diffusion equations in line with the atomistic model, which takes the Kirkendall effect into account intrinsically and efficiently. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the process of maturation of an aqueous solution of L-cysteine and silver nitrate using the method of atomistic molecular dynamics is investigated. To study the maturation process, an atomistic model of the solution was developed. The study allowed to obtain new data on the structure of silver mercaptide clusters and the role of their structural features in the process of further self-organization.

The effect of preparation temperature on the synthesis of high quality graphene oxide (GO) by a chemical oxidation method has been studied. GO samples have been produced from graphite using a blend of sulfuric and phosphoric acids with a volume ratio of 4:1, where potassium permanganate and hydrogen peroxide were selected as oxidizing agents. The temperature for GO preparation was changed over a range of 20–85 °C. The synthesized GO samples have been characterized by X-ray diffraction, scanning electron microscopy, electron dispersive spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible spectroscopy methods. It was shown that high quality GO can be synthesized at 20 °C but the purity of GO increased with the increase of the preparation temperature. The atomistic models of GO sheets prepared at different temperatures and according to the stoichiometric ratio of the functional groups found by XPS have been developed. Based on the developed models it was found that GO prepared at higher temperatures had more holes in the sheets supported with experimental images. [ABSTRACT FROM AUTHOR]

A simplified two length-scale model is applied in direct flexoelectricity for two-dimensional problems. Numerical experiments are performed to obtain the two unknown flexoelectric parameters that appear in gradient theory in elasticity. They are determined by fitting the results from an atomistic model with an analytical solution for a simple problem employing gradient theory, namely, a square domain with a simple polynomial variation of displacements. This is demonstrated by a numerical example for alpha alumina α-Al2O3. [ABSTRACT FROM AUTHOR]

When wood-based activated carbon was tailored with quaternary ammonium/epoxide (QAE) forming compounds (QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid (PFOA) from groundwater. With favorable tailoring, QAE-AC removed PFOA from groundwater for 118,000 bed volumes before half-breakthrough in rapid small scale column tests, while the influent PFOA concentration was 200 ng/L. The tailoring involved pre-dosing QAE at an array of proportions onto this carbon, and then monitoring bed life for PFOA removal. When pre-dosing with 1 mL QAE, this PFOA bed life reached an interim peak, whereas bed life was less following 3 mL QAE pre-dosing, then PFOA bed life exhibited a steady rise for yet subsequently higher QAE pre-dosing levels. Large-scale atomistic modelling was used herein to provide new insight into the mechanism of PFOA removal by QAE-AC. Based on experimental results and modelling, the authors perceived that the QAE's epoxide functionalities cross-linked with phenolics that were present along the activated carbon's graphene edge sites, in a manner that created mesopores within macroporous regions or created micropores within mesopores regions. Also, the QAE could react with hydroxyls outside of these pore, including the hydroxyls of both graphene edge sites and other QAE molecules. This latter reaction formed new pore-like structures that were external to the activated carbon grains. Adsorption of PFOA could occur via either charge balance between negatively charged PFOA with positively charged QAE, or by van der Waals forces between PFOA's fluoro-carbon tail and the graphene or QAE carbon surfaces. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The tacticity of vinyl polymer chains strongly affects the physical properties of polymeric materials, as example the chain conformations and stiffness. In the present work we tested how the hybrid Particle-Field Molecular Dynamics (PF-MD) technique is capable to describe conformational differences of polymer chains as function of the tacticity. In particular, we focus on tacticity effect of atactic, isotactic, and syndiotactic polypropylene (PP) homopolymer melts. We found that PF-MD simulations exhibit dependence of Flory's Characteristic Ratio from the fraction of racemo diads along the PP chains in qualitative agreement with Small Angle Neutron Scattering (SANS) experiments and theoretical previsions. Finally, we calculated and compared the packing length parameter on very high stereoregular syndiotactic PP systems with rheological measurements. A qualitative agreement between the calculated and experimental packing length is found. [ABSTRACT FROM AUTHOR]

In this work, heterostructures formed with vertical stacking of two-dimensional (2D) layered materials are systematically studied. Considering near infrared (NIR)/short-wave-infrared (SWIR) photodetection, van der Waals (vdW) heterostructures with various possible combinations of group-6 and group-7 monolayer transition metal dichalcogenides (TMDs) are explored. Single-layer distorted 1T ReS2, being a dynamically stable semiconducting material, is adopted as the group-7 constituent. On the other hand, as group-6 constituents, five different semiconducting monolayer TMDs, viz., MoS2, WS2, MoSe2, WSe2, and MoTe2 have been chosen. A rational selection of group-6 TMDs based on intrinsic properties of individual materials as well as their heterointerfaces with single-layer ReS2 is demonstrated here to obtain type-II vdW heterostructures which can ensure efficient generation, separation, and collection of charge carriers resulting in significant improvement in photodetection metrics. [ABSTRACT FROM AUTHOR]

[Display omitted] • The developed atomistic model achieves Young's modulus prediction error of under 5% for mesophase pitch-based carbon fibers. • The diverse strengths of interactions among adjacent graphene nanoribbons lead to the emergence of distinct failure modes. • Active graphene edges strengthen the defective region, thus modifying load redistribution and improving structure strength. Mesophase pitch (MPP)-based carbon fibers exhibit outstanding mechanical properties, notably an exceptionally high Young's modulus. Despite extensive investigations into the microstructure of MPP-based carbon fibers, the influence of these factors on deformation mechanisms under tension remains unclear. This study employs the continuous defective graphene nanoribbons (dGNR) atomistic structure model for molecular dynamics simulations to explore the tensile failure mechanisms of MPP-based carbon fibers. In the simulation model, the structure of the defective region was generated through high-temperature annealing, and a transition region was introduced to prevent distortion and damage to the active graphene edges. The simulation reveals the evolutionary process of the microstructure of MPP-based carbon fibers under tension and achieves Young's modulus predictions with greater accuracy than theoretical models. Additionally, the study shows that different strengths of interactions between adjacent graphene nanoribbons can lead to two distinct failure modes. Models with larger crystallite dimensions along the fiber axis and lower average defective concentrations exhibit geometric deformation coordination between adjacent nanoribbons, potentially elucidating the increasing strength trend in MPP-based carbon fibers with rising graphitization levels. Our simulations provide insights into the tensile failure mechanisms of MPP-based carbon fibers, offering valuable guidance for regulating their microstructure to enhance mechanical performance. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • New consistent consistent set of interatomic potentials for monazites and xenotimes. • Errors do not exceed 0.3% in the calculation of structural parameters. • Calculated formation energies of point defects and enthalpy of mixing. • Results are consistent with experimental data. Abstract We have calculated the structural and thermodynamic parameters for solid solutions of lanthanides and plutonium monazites and xenotimes using the developed consistent set of interatomic potentials. We have estimated energies of the point defects of crystal structures. The developed model can be applied for further modelling of radiation stability of Pu-containing monazite using molecular dynamics approach. [ABSTRACT FROM AUTHOR]

Combining atomistic and coarse-grained (CG) models is a promising approach for quantitative prediction of polymer properties. However, the gaps between the length and time scales of atomistic and CG models still need to be bridged. Here, the scale gaps of the atomistic model of polyethylene melts, the bead−spring Kremer−Grest model, and dissipative particle dynamics with the slip-spring model were investigated. A single set of spatial and temporal scaling factors was determined between the atomistic model and each CG model. The results of the CG models were rescaled using the set of scaling factors and compared with those of the atomistic model. For each polymer property, a threshold value indicating the onset of static or dynamic universality of polymers was obtained. The scaling factors also revealed the computational efficiency of each CG model with respect to the atomistic model. The performance of the CG models of polymers was systematically evaluated in terms of both the accuracy and computational efficiency.

Graphical abstract Abstract Semi-coherent cube-on-cube miscible U–Zr interfaces were studied using molecular dynamics simulations. The misfit accommodation of such semi-coherent phase boundaries was characterized by a two-dimensional dislocation network model utilizing a combination of theoretical predictions and analysis of the atomic system. The dislocation networks were discussed for various stacking orientation of the adjoining phases in terms of the composition of the dislocation sets, the partitioning between edge and screw components and the associated residual elastic fields. These analyses showed that the patterning of the network of dislocations forming these phase boundaries results from the competition between a structurally-driven process (i.e., function of the lattice misfit) and a chemically-driven process (i.e., due to the miscibility between U and Zr). [ABSTRACT FROM AUTHOR]

The thermal and dynamical properties Nd 2 Fe 14 B at finite temperatures are studied with an atomic model Hamiltonian. The temperature dependence of the magnetization including the reorientation transition was obtained successfully. Moreover, the atom-specific observation revealed that the Nd magnetic moment decreases fast with the temperature. Temperature dependence of the domain wall structures was also obtained. Beside the static thermal properties, dynamics of the magnetization in unfavorable magnetic field was studied by stochastic LLG equation and Monte Carlo method. The field and size-dependences of the relaxation time at finite temperatures are discussed including the effects of the dipole-dipole interaction. [ABSTRACT FROM AUTHOR]

In this paper, the impact of statistical variability on the accuracy of a propagation delay time compact model (CM) is analyzed. Hence, we aim to select an appropriate CM and extend it in the presence of statistical variability using a number of electrical parameters. Furthermore, we study the impacts of inverter extrinsic parameters (input transition time, load capacitance), environmental parameters (temperature, supply voltage) and device width on propagation delay time variation. The accuracy of extended propagation delay CM is compared with the most accurate results obtained from a library of “atomistic” modelcards. It is shown that both mean and standard deviation (SD) of the propagation delay time almost follow the trend obtained from “atomistic” simulations while changing device width, extrinsic and environmental parameters. The best accuracy occurs when changing device width (W) and load capacitance (CL). In these cases, a minimum error of 0.03 and 0.01 ps for the mean and SD of the propagation delay time is obtained in reference to “atomistic” results, respectively. The least accuracy occurs when changing tr and CL. In these cases, a maximum error of 4.2 and 0.48 ps for the mean and SD of propagation delay time is obtained in reference to “atomistic” results, respectively. [ABSTRACT FROM AUTHOR]

Li-air batteries have attracted interest as energy storage devices due to their high energy and power density. Li-air batteries are expected to revolutionize the automobile industry (for use in electric and hybrid vehicles) and electrochemical energy storage systems by surpassing the energy capacities of conventional Li-ion batteries. However, the practical implementation of Li-air batteries is still hindered by many challenges, such as low cyclic performance and high charging voltage, resulting from oxygen transport limitations, electrolyte degradation, and the formation of irreversible reduction products. Therefore, various methodologies have been attempted to mitigate the issues causing performance degradation of Li-air batteries. Among myriad studies, theoretical and numerical modeling are powerful tools for describing and investigating the chemical reactions, reactive ion transportation, and electrical performance of batteries. Herein, we review the various multi-physics/scale models used to provide mechanistic insights into processes in Li-air batteries and relate these to overall battery performance. First, continuum-based models describing ion transport, pore blocking phenomena, and reduction product precipitation are presented. Next, atomistic modeling-based studies that provide an understanding of the reaction mechanisms in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), as well as ion-ion interactions in the electrolyte, are described. [ABSTRACT FROM AUTHOR]

Symmetry of the source–channel and drain–channel junction is a unique property of a metal-oxide-semiconductor field effect transistor (MOSFET), which needs to be preserved while realizing sub-decananometer channel length devices using advanced technology. Employing experimental-findings-driven atomistic modeling techniques, we demonstrate that such symmetry might not be preserved in an atomically thin phase-engineered MoS2-based MOSFET. It originates from the two distinct atomic patterns at phase boundaries ( $\beta $ and $\beta $ *) when the semiconducting phase (channel) is sandwiched between the two metallic phases (source and drain). We develop a geometrically optimized atomic model of two independent heterophase structures comprising $\beta $ and $\beta $ * interfaces and study their electrical characteristics using density functional theory-nonequilibriumGreen’s function formalism. We further study the effect of semiconductor doping on the transmission of those planar devices and show that irrespective of the doping concentration, these heterophase structures exhibit asymmetric barrier heights. Our findings could be useful for designing integrated circuits using such advanced transistors. [ABSTRACT FROM PUBLISHER]

A general nonlocal coupling technique between an atomistic (AM) model and the bond-based peridynamic (PD) model is proposed, based on the Arlequin framework. This technique applies the complementary weight function and constraint conditions to transmit energies through the overlapping region between the AM and PD regions. We extend the original Arlequin framework to discrete cases by redefining constraint conditions by the peridynamic differential operator, which enables the interpolation and corresponding derivative of scattered data. Besides, the preconditioning of calibration for the PD effective micromodulus is implemented to guarantee the equilibrium of energy. One-dimensional benchmark tests investigate the coupling effects influenced by several key factors, including the coupling length, weight function, grid size and horizon in the PD model, and constraint conditions. Two- and three-dimensional numerical examples are provided to verify the applicability and effectiveness of this coupling model. Results illustrate this AM–PD coupling model takes the mutual advantages of the computational efficiency of PD model and the accuracy of AM model, which provides a flexible extension of the Arlequin framework to couple particle methods. [ABSTRACT FROM AUTHOR]

With the aid of atomistic multiscale modelling and analytical approaches, buckling strength has been determined for carbon nanofibres/epoxy composite systems. Various nanofibres configurations considered are single walled carbon nano tube (SWCNT) and single layer graphene sheet (SLGS) and SLGS/SWCNT hybrid systems. Computationally, both eigen-value and non-linear large deformation-based methods have been employed to calculate the buckling strength. The non-linear computational model generated here takes into account of complex features such as debonding between polymer and filler (delamination under compression), nonlinearity in the polymer, strain-based damage criteria for the matrix, contact between fillers and interlocking of distorted filler surfaces with polymer. The effect of bridging nanofibres with an interlinking compound on the buckling strength of nano-composites has also been presented here. Computed enhancement in buckling strength of the polymer system due to nano reinforcement is found to be in the range of experimental and molecular dynamics based results available in open literature. The findings of this work indicate that carbon based nanofillers enhance the buckling strength of host polymers through various local failure mechanisms. [ABSTRACT FROM AUTHOR]

Performance degradation in a shape memory alloy (SMA) occurs due to dislocation activities at any stage of its thermo-mechanical deformation history. Knowing the physical energy barriers to activate slip could prove instrumental in devising strategies to engineer superior resistance thereto. Given the multi-elements, the SMA slip propensity is intrinsically decided by inherent bonding landscapes. In essence, the problem of theorizing SMA slipping tendency reduces to a quantum mechanical one. Consequently, atomistic calculations can provide invaluable experimentally verifiable material trend as well as potentially pave the way for advancing novel SMAs. [ABSTRACT FROM AUTHOR]

A simple interparticle potential for a set of classical identical particles is used to model martensitic transformations in two dimensions. The influence of the symmetry of the phases involved in the transformation on the reversibility of such process is analyzed. Numerical simulations are used to confirm the theoretical suggestion that a necessary condition for reversibility is that transformations be group-subgroup. [ABSTRACT FROM AUTHOR]

[Display omitted] • The relationship between the chemical shift of W 4f state in amorphous W-B-C materials and local atomic composition near W atoms has been analyzed by means of atomistic models. • Effect of fluctuations of the local atomic density of W on chemical shift has been discovered. • Theoretical findings are consistent with measured chemical shifts in deposited amorphous W-B-C systems. In this paper, we critically evaluate the applicability of the procedure proposed in [Mirzaei et al., Surf. Coat. Technol. 358 (2019) 843–849] which is based on the fitting of the XPS spectrum of amorphous W-B-C material into three components with fixed peak positions to get the relative amount of W-W, W-B, and W-C bonds. We show that W-W bonds substantially influence positions of the peak components. We have verified this assumption by generating a set of models of amorphous W-B-C with different compositions (W:B:C ratio) and calculating the W 4f core electron binding energies employing ab initio methods. This enabled us to formulate the relationship between the W 4f electron binding energies (BE) and the local atomic environments of W atoms. Our analysis confirms the expected W 4f chemical shifts in W-B-C caused by W-B and W-C bonds and reveals that W-W bonds shift the W 4f electronic states in the same direction as W-B bonds, which has substantial implications for the correct interpretation of the measured XPS spectra. [ABSTRACT FROM AUTHOR]

Abstract: We propose a coarse-graining technique to reduce a given atomistic model into an equivalent coarse grained continuum model. The developed technique is tailored for problems involving complex crack patterns in 2D and 3D including crack branching and coalescence. Atoms on the crack surface are separated from the atoms not on the crack surface by employing the centro symmetry parameter. A rectangular grid is superimposed on the atomistic model. Atoms on the crack surface in each cell are used to estimate the equivalent coarse-scale crack surface of that particular cell. The crack path in the coarse model is produced by joining the approximated crack paths in each cell. The developed technique serves as a sound basis to study the crack propagation in multiscale methods for fracture. [Copyright &y& Elsevier]

Abstract: In situ transmission electron microscopy enables the imaging of biological cells, macromolecular protein complexes, nanoparticles, and other systems in a near-native environment. In order to improve interpretation of image contrast features and also predict ideal imaging conditions ahead of time, new virtual electron microscopic techniques are needed. A technique for virtual fluid-stage high-angle annular dark-field scanning transmission electron microscopy with the multislice method is presented that enables the virtual imaging of model fluid-stage systems composed of millions of atoms. The virtual technique is exemplified by simulating images of PbS nanoparticles under different imaging conditions and the results agree with previous experimental findings. General insight is obtained on the influence of the effects of fluid path length, membrane thickness, nanoparticle position, defocus and other microscope parameters on attainable image quality. [Copyright &y& Elsevier]