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The discrete element method (DEM) is employed to investigate the impact of coupling between volumetric and axial strains on the flow liquefaction vulnerability of 3D cubic particulate specimens. The virtual testing program conducted here encompasses a wide range of initial states and varying degrees of coupling between volumetric and axial strains. Utilizing data obtained from DEM simulations, the evolution of micro- and macroscale variables, including coordination number, contact fabric anisotropy, redundancy index, strong force networks, invariants of the effective stress tensor, and excess pore-water pressure, is examined. Results from DEM tests indicate that coupling expansive volumetric strain with axial strain leads to a gradual loosening of the load bearing microstructure, a decrease in coordination number, and a faster change in contact anisotropy. DEM simulations demonstrate that the triggering of flow liquefaction instability is followed by a sudden increase in contact fabric anisotropy and abrupt drops in coordination number and redundancy index. Moreover, a detailed analysis of the findings suggests that the stress ratio at the onset of post-peak softening decreases with increasing expansive volumetric strains. [ABSTRACT FROM AUTHOR]

Nanozymes present promising alternatives to natural enzymes, but controlling nanozymes' performance and employing them for selectively removing antibiotics are extremely challenging. Employing theoretical calculations to design the coordination environments of mental and coordination atoms for directing single‐atom nanozymes synthesis emerges as a promising strategy to enhance their efficiency and selectivity in antibiotic elimination. In this study, the peroxidase‐like specificity of iron single‐atom nanozymes (FeSA‐Nx, x = 2,3, and 4) with specific Fe–N coordination numbers is demonstrated based on theoretical calculations. These calculations guide the synthesis of corresponding ultra‐thin FeSA‐Nx, achieving a high degree of consistency between theoretical predictions and experimental results. FeSA‐N3 with a Fe─N3 coordination number proves to be the most effective. The efficient electron transfer from Fe─N3 site to H2O2 reduces the free energy required for •OH generation. Quantitative structure‐activity relationship (QSAR) analysis reveals a strong positive correlation between degradation efficiency of cephalosporins and their electron‐donating capabilities (R2 = 0.820–0.929), realizing selectively eliminating cephalosporins. Integration FeSA‐N3 into ceramic membrane (FeSA‐N3/CM) improves hydrophilicity, achieving continuous and stable removal of cephalosporin. This study provides valuable insights into coordination number regulating nanozyme properties for selective antibiotics removal and offers novel perspectives for FeSA‐N3 application in integrated systems. [ABSTRACT FROM AUTHOR]

As a non-renewable resource, oil faces increasing demand, and the remaining oil recovery rates in existing oil fields still require improvement. The primary objective of this study is to investigate the impact of pore structure parameters on the distribution and recovery of residual oil after polymer flooding by constructing a digital pore network model. Using this model, the study visualizes the post-flooding state of the model with 3DMAX-9.0 software and employs a range of simulation methods, including a detailed analysis of the pore size, coordination number, pore–throat ratio, and wettability, to quantitatively assess how these parameters affect the residual oil distribution and recovery. The research shows that the change in the distribution of pore sizes leads to a decrease in cluster-shaped residual oil and an increase in columnar residual oil. An increase in the coordination number increases the core permeability and reduces the residual oil; for example, when the coordination number increases from 4.3 to 6, the polymer flooding recovery rate increases from 24.57% to 30.44%. An increase in the pore–throat ratio reduces the permeability and causes more residual oil to remain in the throat; for example, when the pore–throat ratio increases from 3.2 to 6.3, the total recovery rate decreases from 74.34% to 63.72%. When the wettability changes from oil-wet to water-wet, the type of residual oil gradually changes from the difficult-to-drive-out columnar and film-shaped to the more easily recoverable cluster-shaped; for example, when the proportion of water-wet throats increases from 0.1:0.9 to 0.6:0.4, the water flooding recovery rate increases from 35.63% to 51.35%. Both qualitative and quantitative results suggest that the digital pore network model developed in this study effectively predicts the residual oil distribution under different pore structures and provides a crucial basis for optimizing residual oil recovery strategies. [ABSTRACT FROM AUTHOR]

Metallic aerogels, as featured by high surface area, porosity, and self‐supported metal skeleton, are regarded as an ideal platform for developing next‐generation electrocatalysts. However, the precise adjustment of their skeleton nanostructure to enhance catalytic properties remains significantly underexplored. Herein, inspired by the impact of the metal atoms' coordination number on their reactivity, we devised and prepared dendritic Pt aerogels (DPAs) via a facile sol‐gel method. The synergy of aerogel structure and coordinatively distinct catalytic sites from dendritic morphology enables DPAs to exhibit markedly improved electrocatalytic activity and stability for methanol oxidation reaction. The mass activity and specific activity of DPAs are 1.28 A mgPt−1 and 1.5 mA cmPt−2, which are 4.1 and 3.2 times higher than those of commercial Pt/C, respectively. [ABSTRACT FROM AUTHOR]

Cu‐catalyzed electrochemical CO2 reduction reaction (CO2RR) produces multi‐carbon (C2+) chemicals with considerable selectivities and activities, yet required high overpotentials impede its practical application. Here, we design interfaces with abrupt coordination number (CN) changes that greatly reduce the applied potential for achieving high C2+ Faradaic efficiency (FE). Encouraged by the mechanistic finding that the coupling between *CO and *CO(H) is the most probable C−C bond formation path, we use Cu2O‐ and Cu‐phthalocyanine‐derived Cu (OD−Cu and PD−Cu) to build the interface. Using operando X‐ray absorption spectroscopy (XAS), we find that the Cu CN of OD−Cu is ~11, favoring CO* adsorption, while the PD−Cu has a COH*‐favorable CN of ~4. Operando Raman spectroscopy revealed that the interfaces with abrupt CN changes promote *OCCOH formation. As a result, the designed catalyst achieves a C2+ FE of 85±2 % at 220 mA cm−2 in a zero‐gap CO2 electrolyzer. An improvement of C2+ FE by 3 times is confirmed at the low potential regime where the current density is 60–140 mA cm−2, compared to bare OD−Cu. We report a 45‐h stable CO2RR operation at 220 mA cm−2, producing a C2+ product FE of ~80 %. [ABSTRACT FROM AUTHOR]

The particle dynamics model of MRFs (MRFs) is based on the discrete element technique, which takes into account essential MRF variables such as magnetic field, particle parameters, particle volume fraction, carrier fluid properties, and other parameters. Firstly, to digitally characterize the microstructure of MRFs, the particle coordination number, as a new perspective is creatively proposed. The validity and predictability of the created model are then tested in conjunction with the rheological performance studies by comparing it to the known continuous medium model. Finally, based on the proposed model, the influence of each influencing factor on the magnetorheological effect is simulated and regularity analysis is given from the perspective of particles. Linking macroscopic qualities and MRF microstructure, which offers a theoretical basis for the preparation of MRFs with improved performance and prediction of performance under various working situations. [ABSTRACT FROM AUTHOR]

We explore the structural properties of Mg, MgO, and MgSiO3 liquids from ab initio computer simulations at conditions that are relevant for the interiors of giant planets, stars, shock compression measurements, and inertial confinement fusion experiments. Using path-integral Monte Carlo and density functional theory molecular dynamics, we derive the equation of state of magnesium-rich liquids in the regime of condensed and warm dense matter, with densities ranging from 0.32 to 86.11 g cm−3 and temperatures from 20,000 K to 5 × 108 K. We study the electronic structure of magnesium as a function of density and temperature and the correlations of the atomic motion, finding an unexpected local maximum in the pair correlation functions that emerges at high densities which decreases the coordination number of elemental magnesium and reveals a higher packing. This phenomenon is not observed in other magnesium liquids, which maintain a rather constant coordination number.

The discrete element method (DEM) is used widely to study the crushing behaviour of granular materials from a microscale perspective. However, a crushing criterion that can be suitable for triggering particle crushing for different coordination numbers (CNs) is still lacking. To develop a crushing criterion, particle crushing tests are conducted for different CNs via the DEM. Crushable spherical agglomerates are made by bonding smaller sub-spheres. Based on the results of simulations, a new crushing criterion invariant to the coordination number effect is proposed. The crushing criterion is simply expressed in terms of the three principal stresses of the particles. Furthermore, the applicability of the criterion is verified under various conditions, such as different numbers of sub-sphere, shapes of particles, microscale parameters and loading patterns. By using the new criterion, the particle strengths obtained from the single particle crushing tests can be used as the crushing strengths for the particles under multiple contact loading conditions in DEM simulations. [ABSTRACT FROM AUTHOR]

Chalcogenide composites, a category of non-oxide glasses, have shown great potential in various applications such as optoelectronics, thermal imaging, memory-switching devices, lasers, and more. Owing to the distinctive physical properties inherent in chalcogenide glasses, these materials have garnered significant interest across various technological domains. This study aims to analyze the impact of incorporating sulfur (S) and antimony (Sb) into (S3Sb2)x(S2Ge)100−x:x = 10, 20, 30 chalcogenide composites, assessing their radiation shielding, structural, physical, and electrical properties. Three distinct composites, designated as SSbGe-10, SSbGe-20, and SSbGe-30, are irradiated with gamma photons across an energy range of 0 to 15 MeV. The assessment of the radiation shielding attributes is conducted through the utilization of the FLUKA Monte Carlo (MC) Code. Phillips and Thorpe's theory is employed to analytically estimate structural and physical attributes such as Coordination Number (CN), bond-bending constraints (NS), bond-stretching constraints (NC), constraints Number (Ncons), Floppy mode (F), and stoichiometry (R). The electrical features of the provided specimens are analyzed through the utilization of the effective electron conductivity (Ceff), as ascertained by the Phy-X: PSD software. The findings indicate that the augmentation of the x value within the range of 10–30 wt.% positively augments the gamma photon shielding efficacy of the composite materials. Both NS and NC demonstrate diminishing patterns, encompassing the range of 2.64 to 2.575 and 7.56 to 7.30, respectively. Additionally, the stoichiometry (R > 1) for the investigated samples indicates that the chosen glasses are rich chalcogenide composites. The exhaustive examination of the physical, radiation shielding, and electrical characteristics of the prepared chalcogenide glasses provides valuable insights for subsequent investigations into various chalcogenide glass formulations. [ABSTRACT FROM AUTHOR]

It is essential to probe the coordination number (CN) because it is a crucial factor to ensure the catalytic capability of single‐atom catalysts (SACs). Currently, synchrotron X‐ray absorption spectroscopy (XAS) is widely used to measure the CN. However, the scarcity of synchrotron X‐ray source and complicated data analysis restrict its wide applications in determining the CN of SACs. In this contribution, we have developed a d‐band center‐regulated acetone cataluminescence (CTL) probe for a rapid screening of the CN of Pt‐SACs. It is disclosed that the CN‐triggered CTL is attributed to the fact that the increased CN could induce the downward shift of d‐band center position, which assists the acetone adsorption and promotes the subsequent catalytic reaction. In addition, the universality of the proposed acetone‐CTL probe is verified by determining the CN of Fe‐SACs. This work has opened a new avenue for exploring an alternative to synchrotron XAS for the determination of CN of SACs and even conventional metal catalysts through d‐band center‐regulated CTL. [ABSTRACT FROM AUTHOR]

Experimental studies on the nature of chemical bonding in manganese silicate systems were carried out in photoelectron spectrometer ES-2402. It was established that the change in the binding energy of the core electronic levels of the atoms of the elements is subject to the general patterns of changes in the electronic structure and chemical characteristics within the Periodic System of elements. Additional data on the chemical bond energy of silicon in complex compounds of MnO–SiO2 and MnO–CaO–SiO2 were obtained. [ABSTRACT FROM AUTHOR]

Highlights The reaction mechanisms of hydrogen evolution reaction (HER) on various crystal surfaces of zinc anode have been systematically investigated by first-principle calculations. Both the thermodynamic and kinetic aspects of HER have been studied to reveal the relative HER activity of several crystal surface of zinc anode. The generalized coordination number of surface Zn atoms are proposed as a key descriptor of HER activity of Zn anode.

Pulsed electrodeposition modes allowed to obtain amorphous Co-W alloys. Using X-ray phase and spectral analysis methods, it was established that the deposition modes and the concentration of the amorphizing component (sodium tungstate salts) in an aqueous electrolyte solution affect the amorphization of alloys. The short-range atomic order was studied by X-ray diffraction analysis and the sizes of the regions of ordered arrangement of atoms were determined in X-ray amorphous Co-W alloys obtained by pulsed electrodeposition. The radial distribution function of atoms was analysed. The assumption is made that cobalt and tungsten atoms combine into configurations that are irregular polyhedrons.

As a non-renewable resource, oil faces increasing demand, and the remaining oil recovery rates in existing oil fields still require improvement. The primary objective of this study is to investigate the impact of pore structure parameters on the distribution and recovery of residual oil after polymer flooding by constructing a digital pore network model. Using this model, the study visualizes the post-flooding state of the model with 3DMAX-9.0 software and employs a range of simulation methods, including a detailed analysis of the pore size, coordination number, pore–throat ratio, and wettability, to quantitatively assess how these parameters affect the residual oil distribution and recovery. The research shows that the change in the distribution of pore sizes leads to a decrease in cluster-shaped residual oil and an increase in columnar residual oil. An increase in the coordination number increases the core permeability and reduces the residual oil; for example, when the coordination number increases from 4.3 to 6, the polymer flooding recovery rate increases from 24.57% to 30.44%. An increase in the pore–throat ratio reduces the permeability and causes more residual oil to remain in the throat; for example, when the pore–throat ratio increases from 3.2 to 6.3, the total recovery rate decreases from 74.34% to 63.72%. When the wettability changes from oil-wet to water-wet, the type of residual oil gradually changes from the difficult-to-drive-out columnar and film-shaped to the more easily recoverable cluster-shaped; for example, when the proportion of water-wet throats increases from 0.1:0.9 to 0.6:0.4, the water flooding recovery rate increases from 35.63% to 51.35%. Both qualitative and quantitative results suggest that the digital pore network model developed in this study effectively predicts the residual oil distribution under different pore structures and provides a crucial basis for optimizing residual oil recovery strategies.

Highlights: The reaction mechanisms of hydrogen evolution reaction (HER) on various crystal surfaces of zinc anode have been systematically investigated by first-principle calculations. Both the thermodynamic and kinetic aspects of HER have been studied to reveal the relative HER activity of several crystal surface of zinc anode. The generalized coordination number of surface Zn atoms are proposed as a key descriptor of HER activity of Zn anode. Hydrogen evolution reaction (HER) has become a key factor affecting the cycling stability of aqueous Zn-ion batteries, while the corresponding fundamental issues involving HER are still unclear. Herein, the reaction mechanisms of HER on various crystalline surfaces have been investigated by first-principle calculations based on density functional theory. It is found that the Volmer step is the rate-limiting step of HER on the Zn (002) and (100) surfaces, while, the reaction rates of HER on the Zn (101), (102) and (103) surfaces are determined by the Tafel step. Moreover, the correlation between HER activity and the generalized coordination number ( CN ¯ ) of Zn at the surfaces has been revealed. The relatively weaker HER activity on Zn (002) surface can be attributed to the higher CN ¯ of surface Zn atom. The atomically uneven Zn (002) surface shows significantly higher HER activity than the flat Zn (002) surface as the CN ¯ of the surface Zn atom is lowered. The CN ¯ of surface Zn atom is proposed as a key descriptor of HER activity. Tuning the CN ¯ of surface Zn atom would be a vital strategy to inhibit HER on the Zn anode surface based on the presented theoretical studies. Furthermore, this work provides a theoretical basis for the in-depth understanding of HER on the Zn surface. [ABSTRACT FROM AUTHOR]

The current work concerned the thermal characteristic of Se0.75−xTe0.25Agx (0 ≤ x ≤ 0.1) chalcogenide glasses. Under non-isothermal conditions, differential scanning calorimetry has been used to evaluate the thermal stability of these compositions throughout the temperature identification of the glass transition, Tg, the initial crystallization temperature, Tin, the peak crystallization rate, Tp, and the melting temperature, Tm. Also, the kinetic factor Kr(T) is specified as a further indication of thermal stability. It was found that the Se0.71Te0.25Ag0.04 has the greatest capacity to form glass and the greatest glass thermal stability between these compositions. These findings have been explained using the average coordination numbers of the tested compositions. Also, in this work, we studied the crystallization kinetic of Se0.75−xTe0.25Agx (0 ≤ x ≤ 0.1) thick films via measuring the sheet resistance, Rs whose thickness is 1000 nm at heating rate 5 K min−1, in the 300–630 K temperature range. Two significant regions might be detected in the sheet resistance curve using this range and by considering how sheet resistance is derived according to temperature, one crystallization area is clearly present for the investigated films. The Avrami index was measured for both alloys and thick films. [ABSTRACT FROM AUTHOR]

High-performance single-atomic Ir catalysts can significantly reduce the cost of proton exchange membrane water electrolysis catalysts due to their ultrahigh atomic utilization. However, difficulties remain for a thorough understanding of the coordination structures and their impact on the electrocatalytic oxygen evolution (OER) catalytic activities. In this study, a series of single Ir–Ox catalysts with different coordination numbers (Ir–Ox, where x represents the O coordination number) are simulated using density functional theory calculations, and the effect of coordination number variation on the catalyst performance is investigated. The results show that the optimized electronic structure of the single Ir–O5 coordination structure significantly reduces the free energy barrier of the rate-determining step and improves the OER catalytic activity of the catalyst by promoting electron transfer and optimizing *O intermediate adsorption. Guided by these results, we successfully prepared the single Ir–O5 structure by introducing Ir into Co3O4. At a current density of 10 mA/cm2, the electrocatalyst exhibits an overpotential of 266 mV, which is 40 mV lower than that of IrO2 with an Ir–O6 coordination structure. Additionally, the catalyst demonstrates excellent stability, maintaining uninterrupted operation for 900 h at a current density of 20 mA/cm2. These findings provide a theoretical basis for the preparation of high-performance iridium oxide catalysts. [ABSTRACT FROM AUTHOR]

This study investigates pore distribution and permeability behavior of tar-rich coal following high-temperature pyrolysis at 500°C using X-ray computed tomography (CT) scanning. Coal samples post-pyrolysis were CT scanned, generating 1755 cross-sectional slices for three-dimensional reconstruction. An axial algorithm extracted pore distribution features, and geometric parameters were computed. An Equivalent Pore Network Model analyzed permeability characteristics. The results show that Post-pyrolysis pore distribution in tar-rich coal exhibited nonuniformity with a significant range in pore size distribution. Pores displayed concentrated spatial patterns. Total porosity was 14.24%, with 12.34% being connected. Most pores in Representative Elementary Volume (REV) regions fell within 10-50 μιτι in width and 20-60 pm in length, constituting over 40% of the total. Pore surface area peaked between 200-100 pm2, also comprising over 40% of the total. The Pore Network Model showed distinct characteristics in two REV regions: REV-1 demonstrated an early stage of development with poor connectivity, while REV-2 displayed a well-developed network with a bimodal coordination number histogram. The study highlights nonuniform post-pyrolysis pore distribution and significant pore size variations in tar-rich coal. This study is crucial for understanding permeability behavior in tar-rich coal after high-temperature pyrolysis. [ABSTRACT FROM AUTHOR]

The published results of various research methods and own experimental data on the structural characteristics of the nearest environment of zinc, cadmium, and mercury ions in aqueous solutions of their salts under standard conditions are summarized. Structural parameters, such as coordination numbers, interparticle distances, characteristics of the second coordination spheres, and ion association types, are discussed. Conclusions are drawn about the effect of ion radius on structure formation in solutions for this group of d-elements. [ABSTRACT FROM AUTHOR]

The express method for evaluating the porous structure of ceramic materials was refined by replacing a smooth change in gas pressure with a stepwise change. After determining the average radius, the maximum radius was determined using the pressure drop until only one chain of gas bubbles remained. The average coordination number for the solid phase and the coefficient of capillary tortuosity were calculated. The experimental and calculated mean radii are in good agreement, whereas the tortuosity coefficients differ. [ABSTRACT FROM AUTHOR]

Amorphous, glassy or disordered materials play important roles in developing structural materials from metals or ceramics, devices from semiconductors or medicines from organic compounds. Their local structure is frequently similar to crystalline ones. A computer program is presented here that runs under the Windows operating system on a PC to extract pair distribution function (PDF) from electron diffraction in a transmission electron microscope (TEM). A polynomial correction reduces small systematic deviations from the expected average Q-dependence of scattering. Neighbor distance and coordination number measurements are supplemented by either measurement or enforcement of number density. Quantification of similarity is supported by calculation of Pearson's correlation coefficient and fingerprinting. A rough estimate of fractions in a mixture is computed by multiple least-square fitting using the PDFs from components of the mixture. PDF is also simulated from crystalline structural models (in addition to measured ones) to be used in libraries for fingerprinting or fraction estimation. Crystalline structure models for simulations are obtained from CIF files or str files of ProcessDiffraction. Data from inorganic samples exemplify usage. In contrast to previous free ePDF programs, our stand-alone program does not need a special software environment, which is a novelty. The program is available from the author upon request. [ABSTRACT FROM AUTHOR]

The orientation of, and contacts between, grains of sand reflect the processes that deposit the sands. Grain orientation and contact geometry also influence mechanical properties. Quantifying and understanding sand microstructure thus provide an opportunity to understand depositional processes better and connect microstructure and macroscopic properties. Using x-ray computed microtomography, we compare the microstructure of naturally-deposited beach sands and laboratory sands created by air pluviation in which samples are formed by raining sand grains into a container. We find that naturally-deposited sands have a narrower distribution of coordination number (i.e., the number of grains in contact) and a broader distribution of grain orientations than pluviated sands. The naturally-deposited sand grains orient inclined to the horizontal, and the pluviated sand grains orient horizontally. We explain the microstructural differences between the two different depositional methods by flowing water at beaches that re-positions and reorients grains initially deposited in unstable grain configurations.

A structural model of two-fraction ceramic dispersions in the form of two single fraction subsystems is proposed. The first contains a given volume fraction of spherical large particles interconnected mainly through a matrix phase consisting of small particles, aerosil and SAS (surface active substances). The second subsystem includes just small particles of quartz and aerosil with an average particle diameter of less than one micron, and the second matrix phase is formed by water and surfactants. The second subsystem forms an endless network between large quartz particles, maintaining these particles in suspension. The model permits calculation of the average coordination numbers and distances between particles in both systems. [ABSTRACT FROM AUTHOR]

This study investigates pore distribution and permeability behavior of tar-rich coal following high-temperature pyrolysis at 500°C using X-ray computed tomography (CT) scanning. Coal samples post-pyrolysis were CT scanned, generating 1755 cross-sectional slices for three-dimensional reconstruction. An axial algorithm extracted pore distribution features, and geometric parameters were computed. An Equivalent Pore Network Model analyzed permeability characteristics. The results show that Post-pyrolysis pore distribution in tar-rich coal exhibited nonuniformity with a significant range in pore size distribution. Pores displayed concentrated spatial patterns. Total porosity was 14.24%, with 12.34% being connected. Most pores in Representative Elementary Volume (REV) regions fell within 10–50 μm in width and 20–60 μm in length, constituting over 40% of the total. Pore surface area peaked between 200–100 μm2, also comprising over 40% of the total. The Pore Network Model showed distinct characteristics in two REV regions: REV-1 demonstrated an early stage of development with poor connectivity, while REV-2 displayed a well-developed network with a bimodal coordination number histogram. The study highlights nonuniform post-pyrolysis pore distribution and significant pore size variations in tar-rich coal. This study is crucial for understanding permeability behavior in tar-rich coal after high-temperature pyrolysis.

Particle breakage in sands can cause significant changes in particle-scale characteristics and is associated with many geotechnical engineering applications. The breakage behavior of loose silica sands sheared under high-pressure loading is studied using X-ray microtomography. Increases in confining pressure cause a significant strain hardening throughout the stress–strain curve, which is directly related to the successive particle breakage. A variety of particle-scale characteristics are quantitatively analyzed based on the CT images, including particle fracture, particle size, fractal dimension, particle shape, and coordination number. Splitting and chipping failure modes are more likely to occur by the external force bridging fewer particles. The fractal condition for particles smaller than 0.4 mm demonstrated that more breakage events occur in the smaller particles rather than larger particles. Particle shape shows an exponential relationship with the breakage indices regardless of the stress path. Meanwhile, the influence of particle breakage is more sensitive to sphericity and convexity than the aspect ratio. The evolution of the coordination number is quite size-dependent, and the larger particles tend to have a higher coordination number for all scans. In the shear stage, significant particle breakage causes a decrease in the mean coordination number, indicating that smaller particles with lower coordination numbers exist in the manner of filling the gaps between the larger particles. [ABSTRACT FROM AUTHOR]

In this work, we present, the concentration-dependent solvation structure and dynamics of an ammonium nitrate (AN) ion pair in aqueous media by means of classical molecular dynamics simulations. Structural properties were investigated by computing the potentials of mean force (PMFs), radial distribution functions (RDFs), cluster size distribution functions, and hydrogen bond dynamics. The change in the depth of the contact ion pair (CIP) and solvent-separated ion pair minima (SSIP) is marginal, whereas for the solvent-assisted ion pair (SAIP) is more stable at lower salt concentrations. The marginal difference in the depth of the CIP minimum of the PMF is explained based on cluster size distribution and hydrogen bonding. The solvation structure of the ions is not affected by the salt concentration. Ab-initio and classical molecular dynamics simulations (both constrained and unconstrained) give similar results for the solvation structure around the cation and the anion. The spatial density distribution functions of the anions around the cations show that the anions occupy the space around the ammonium hydrogen atoms. Profound differences in dynamical properties are found in the case of concentrated solutions as compared to dilute solutions. [ABSTRACT FROM AUTHOR]

The objective of the present work is to investigate the behavior of dumbbell-shaped particles in a cylindrical container subjected to vertical vibration. Particles with different aspect ratios in the commercially used LabRAM mixer (Resodyn Acoustic Mixers, Inc., MT, USA) are selected for the present study. Simulations are performed for different amplitudes of the vibrating platform. Particle properties are assumed to be same as that of potassium chloride (KCl). Simulations are performed in two stages. Particles are initially poured into the container and allowed to settle under gravity. Vibration is switched on after the particles are settled. It is observed that the mean coordination number of particles in packed state, increases with the increase in aspect ratio. Only for particles of lower aspect ratio, kinetic energy of the system increases with the increase in vibrational amplitude. Simulation results also show that the anisotropy observed in the mean squared fluctuations of translational velocity reduces with the increase in vibrational amplitude. [ABSTRACT FROM AUTHOR]

The packing of spherical particles and the granular characteristics of powder batch containing both plastic iron and elastic cast iron are investigated. The inertial shaping of iron parts is analyzed. It is difficult to ensure that the density of the elastoplastic batch varies in proportion to the pressure applied, since compaction of the powder occurs by different mechanisms at different stages of pressing. [ABSTRACT FROM AUTHOR]

Trapped or residual air (or gas) is known to affect the multiphase hydraulic properties of both soils and rocks. Trapped air is known to impact many vadose zone hydrologic applications such as infiltration and flow in the capillary fringe, but is also a major issue affecting recoverable oil reserves. Although many studies have focused on the relationship between porosity and trapped gas saturation (Sgt) in sandstones, far fewer studies have been carried out for carbonate rocks. This work aims to analyze the influence of porous media properties on trapped gas saturation in carbonate rocks. For this we used thirteen Indiana Limestone and Silurian dolomite rock samples from the USA, and several coquinas from the Morro do Chaves formation in Brazil. Pore size distributions were obtained for all samples using Nuclear Magnetic Resonance (NMR), and Mercury Injection Capillary Pressure (MICP) data from three of the samples to determine their pore throat size distributions. Additionally, 3D microtomography (microCT) images were used to quantify macropore profiles and pore connectivities. Results indicate a lower capacity of gas trapping in carbonate rocks in which micro- and mesopores predominate. Results also indicate that in carbonate rocks, pore size exerts a greater influence on the ability of gas trapping compared to pore connectivity, so that rocks with a predominance of macropores have greater capacity for gas trapping, even when the macropores are well interconnected. These findings show that pore characteristics very much affect the processes governing gas trapping in carbonate rocks, and indirectly the multiphase hydraulic properties and recoverable oil reserves of carbonate rock reservoirs.

Roundness/angularity is a vital shape descriptor that significantly impacts the mechanical response of granular materials and is closely associated with many geotechnical problems, such as liquefaction, slope stability, and bearing capacity. In this study, a series of biaxial shearing tests are conducted on dual-size aluminum circular and hexagonal rod material. A novel image analysis technique is used to estimate particle kinematics. A discrete element model (DEM) of the biaxial shearing test is then developed and validated by comparing it with the complete experimental data set. To systematically investigate the effect of roundness/angularity on granular behavior, the DEM model is then used to simulate eight non-elongated convex polygonal-shaped particles. Macroscopically, it is observed that angular assemblies exhibit higher shear strengths and volumetric deformations, i.e., dilations. Moreover, a unique relationship is observed between the critical state stress ratio and particle roundness. Microscopically, the roundness shows a considerable effect on rotational behavior such that the absolute mean cumulative rotation at the same strain level increases with roundness. A decrease in roundness results in relatively stronger interlocking, restricting an individual particle’s free rotation. Furthermore, the particles inside the shear band exhibit significantly higher rotations and are always associated with low coordination numbers. Generally, the geometrical shape of a particle is found to have a dominant effect on rotational behavior than coordination number. [ABSTRACT FROM AUTHOR]

The paper presents an effective, robust and geometrically invariants, collection of contours or boundaries base local binary pattern (LBP) for binary object shape retrieval and classification. The contours segmentation or deformations of an object is a preprocessing step of shape retrieval and classification that segment the binary object shape in a shape-preserving sequence of contours segment using a coordination number shape segmentation approach. The proposed local binary pattern extracts the minimum decimal value corresponding to the pattern of object contour points for each and every contours segment. It is one of the most important features in content-based image retrieval. At the matching stage, we find Euclidean distance between eigenvalues of correlation coefficient of Hu's seven moments corresponding to each contour segment for given two objects. The LBP pattern corresponding to the image contour provides excellent power, which is demonstrated by excellent retrieval performance on several popular shape benchmarks, including MPEG-7 CE-Shape-1 dataset and Kimia's dataset. Experimental results obtained from popular databases demonstrate that the proposed linear binary pattern can achieve comparably better results than existing algorithms. [ABSTRACT FROM AUTHOR]

We have carried out in situ high‐pressure acoustic velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass up to pressures of 155 GPa, which confirmed a distinct pressure‐induced trend change in the transverse acoustic velocity (VS) profile around 98 GPa, likely caused by the Si‐O coordination number (CN) change from 6 to 6+. Although it has been reported that the substitution of Fe2+ in MgSiO3 glass induces almost linear velocity reduction up to ∼160 GPa, we revealed that the VS profile of (Fe2+, Al)‐bearing MgSiO3 becomes anomalously steeper above ∼100 GPa and eventually came to be equivalent to MgSiO3 glass above ∼125 GPa. This implies the incorporation of Al into Fe‐bearing MgSiO3 glass significantly facilitates making it far elastically stiffer and thus the densification under pressures well within the Earth's lower mantle. Our results indicate the possible presence of stiff and highly dense silicate melts in deep MOs in the rocky terrestrial planets. Plain Language Summary: Since the terrestrial planets are thought to have gone through multiple episodes of magma ocean (MO) in their formation processes, clarifying the structure and physical properties of silicate melts under relevant deep MO conditions is crucial to understanding the internal structure and evolution of the terrestrial planets. Our in situ high‐pressure acoustic velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass, used as a structural analog of silicate melts, shows both Al and Fe2+ are very effective to reduce the pressure corresponding to the Si‐O CN change from 6 to 6+. In addition, a few percentages of Al incorporation could make the Fe‐bearing MgSiO3 glass significantly far elastically stiff and thus dense with 6+ CN in Si‐O in the deep terrestrial interiors. The presence of stiff and highly dense silicate melts in deep MOs in the terrestrial planets would offer essential insights into the MO convection, gravitational stability of silicate melts in the course of MO crystallization, and the mantle stratification of the terrestrial planets. Key Points: We have carried out acoustic wave velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass up to 155 GPaVS profile displays a change at 98 GPa induced by the Si‐O coordination number change from 6 to 6+ followed by anomalously steeper trendResults indicate the possible presence of highly dense Al, Fe2+‐bearing Si‐rich melts in the deep terrestrial magma oceans [ABSTRACT FROM AUTHOR]

The reduction of alkynyl‐silver and phosphine‐silver precursors with a weak reducing reagent Ph2SiH2 led to the formation of a novel silver nanocluster [Ag93(PPh3)6(C≡CR)50]3+ (R=4‐CH3OC6H4), which is the largest structurally characterized cluster of clusters. This disc‐shaped cluster has a Ag69 kernel consisting of a bicapped hexagonal prismatic Ag15 unit wrapped by six Ino decahedra through edge‐sharing. This is the first time that Ino decahedra are used as a building block to assemble a cluster of clusters. Moreover, the central silver atom has a coordination number of 14, which is the highest in metal nanoclusters. This work provides a diverse metal packing pattern in metal nanoclusters, which is helpful for understanding metal cluster assembling mechanisms. [ABSTRACT FROM AUTHOR]

The structural parameters of the rare-earth diacetate halide trihydrates, RE(OAc)2Hal·3H2O with RE = Ce − (Pm) − Lu and Hal = Cl, Br, have been determined by low temperature, high-resolution SCXRD in order to examine the effect of lanthanide contraction on the coordination geometry in this series of isomorphous compounds consisting of cationic, acetate-bridged, non-linear, one-dimensional coordination polymers of composition [RE(H2O)3(OAc)2]+ and laterally hydrogen bonded halide ions, Hal−. Although the shrinkage of the unit cell volume follows lanthanide contraction very well over the complete range of investigated RE elements, many other parameters (i.e., lattice constants, angles and distances in the RE··· RE alignment, RE-O bond lengths, etc.) exhibit a more complex response on lanthanide contraction often expressed by sigmoid curves that can be ascribed to a continuous transition from CN9 (RE = Ce) to CN8 (RE = Lu) as one acetate group loses the chelate function, an effect accompanied by significant structural changes of the carboxylate group. Therefore, data are best analyzed by use of two subsets represented by the two different structure types of Ce and Lu, the structural features of which change with decreasing/increasing the size of RE3+, up to the borderline between both subsets. [ABSTRACT FROM AUTHOR]

Internal instability means that finer particles pass through the constrictions of coarser particles at a hydraulic gradient well below that of heave or piping, rendering the soil ineffective for its intended purpose. The soil could make a transition from an internally stable state to an unstable state or vice versa due to shear-induced deformation. The discrete element method (DEM) is adopted in this study to examine and quantify soil behavior by simulating the quasi-static shear deformation of internally stable and unstable soils at the micro- and macroscales. The dense bimodal specimens were sheared under drained conditions following a constant mean stress path in order to investigate the influence of stress heterogeneity. At the macroscale, the peak deviatoric stress was found to be a function of the fines content and the initial void ratios of the specimens. The development of the average number of contacts per particle and the stress transfer to the finer fraction during shearing are discussed. The simulation results innovatively show that a dense specimen could undergo a transition from an internally stable to an unstable soil as it dilates during shear. These numerical results have significant implications on the importance of real-life situations, such as predicting mud pumping in railroad tracks. Microscale investigations enabled a better understanding of the mechanism of internal instability of soil, which can be helpful in the design and construction of substructures in railways. To demarcate internally unstable and stable soils, the microscale criterion based on the coordination number and the stress reduction factor can be used to estimate the probability of internal instability in the field at different stress state. Internal instability is a problem in railways that results in significant maintenance costs. The findings of this study can be used to avoid the huge maintenance cost associated with internally unstable capping layer in railways. [ABSTRACT FROM AUTHOR]

Quantitative characteristics of the nearest environment of ions in aqueous solutions of cadmium chloride and nitrate are determined by X-ray diffraction analysis in a wide range of concentrations under standard conditions. It is found that, in the studied systems, the coordination number of the cation increases with dilution from 4 to 6. The structure of solutions in the entire studied range of concentrations is determined by ionic associates of the contact type. In solutions of cadmium nitrate, the nitrate ion is monodentately coordinated to the cation. [ABSTRACT FROM AUTHOR]

Sand is a particulate material but is treated as a continuum solid in some engineering analyses. This approach is proven to be acceptable when dealing with geotechnical structures, provided an adequate factor of safety is applied so that there is no risk of failure. However, the continuum approach does not account for the effect of interparticle forces on the micro–macro behaviour of sand. Sand could be modelled as a particulate material using the discrete element method (DEM), taking into account its discrete nature. This paper shows how the microscopic contact properties between the idealised sand particles influence the macro-mechanical behaviour, highlighting the development of the fabric as the soil approaches failure. Thirty DEM biaxial tests were performed to study the sensitivity of the macro–micro mechanical properties of sand to the inter-particle properties of an idealised sand particle. The conditions of these simulations were the same (e.g., particle size distribution, number of particles, porosity after radius enlargement, boundary conditions, and rate of loading). The sensitivity of the pre-peak, peak, and post-peak behaviour of these simulations to the inter-particle properties of an idealised sand particle was studied. Two extra DEM biaxial tests under different confining pressures were performed to verify the cohesionless nature of the synthetic material used for this study. Since a two-dimensional DEM is used for this study, a detailed approach to interpret the results assuming either a plane strain or a plane stress situation was discussed. This study highlighted the critical inter-particle properties and the range over which these influence macro-mechanical behaviour. The results show that Young's modulus is mainly dependent on the normal contact stiffness, and peak stress and the angle of internal friction are greatly dependent on the inter-particle coefficient of friction, while Poisson's ratio and volumetric behaviour of particulate sand are dictated mainly by shear contact stiffness. A set of relationships were established between inter-particle properties and macro-machinal parameters such as Young's modulus, Poisson's ratio, and angle of internal friction. The elastoplastic parameters obtained from these tests are qualitatively in agreement with the typical medium and dense sand behaviour. [ABSTRACT FROM AUTHOR]

Coordination or local environments have been used to describe, analyze and understand crystal structures for more than a century. Here, a new tool called ChemEnv, which can identify coordination environments in a fast and robust manner, is presented. In contrast to previous tools, the assessment of the coordination environments is not biased by small distortions of the crystal structure. Its robust and fast implementation enables the analysis of large databases of structures. The code is available open source within the pymatgen package and the software can also be used through a web app available on http://crystaltoolkit.org through the Materials Project.

In this paper, we have used the hot isostatic pressing HIP models previously carried out for the study of the random dense packing densification (RDP) of spherical particles of the same size in order to adapt them to the RDP of two-dimensional spherical particles. A new microscopic approach is thus developed that allows the densification parameters of two-dimensional spherical powder aggregates to be evaluated as a function of the relative density, taking into account the morphological changes of the powder particles and the porosity. The equations obtained for each parameter (coordination number, mean contact area and effective pressure) made it possible to represent the results in the form of curves. These show that our new approach is well adapted to a realistic description of the densification of powder aggregates with particles of more or less similar sizes.

According to the experimental values of the propagation velocities of longitudinal and transverse ultrasonic waves, the Poisson's ratio of polyurethane systems filled with metal particles was determined. For such systems, the Poisson's ratio is negative. Its value for metal-filled polymer auxetics with polyurethane matrix allowed to determine fractal dimensions and critical percolation indices. This approach made it possible to clarify the features of structure formation in polymer auxetics. It is shown that the fractal-percolation characteristics of these systems are determined by the type of metal filler and the size of its particles.