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Si nanocluster formation during rapid cooling from high temperature Si vapors and its subsequent interaction with substrate was simulated by molecular dynamics. It was confirmed that several nm sized clusters with a loosely bound structure form during rapid cooling and their metastable structures are retained even at temperatures below the Si melting point. Such globular clusters tend to rearrange themselves upon impingement to be a similar structure to that of the substrate, at least near the cluster/substrate interface. This is suggestive of the role of clusters formed under the mesoplasma condition as growth precursors for fast rate epitaxy. [ABSTRACT FROM AUTHOR]

The solid-state bonding of ultralow-carbon steels was conducted by hot pressing and subsequent isothermal holding at low temperatures ranging from 873 to 923 K. The evolution of the interfacial strength was found to consist of two stages; the first stage, where the increase in interfacial strength is rapid and significant, and the second stage, where the increase is gradual. The evolution of strength in the first stage primarily takes place in contact regions produced by hot pressing. In the second stage, on the contrary, the evolution seems to result from the increase in the contact regions due to the shrinkage of voids. A molecular dynamics simulation was performed to clarify the atomic behaviour at the interface during the first stage. The results revealed that the disordered atomic arrangement caused by compression was rearranged with increasing isothermal holding time, leading to improved coherency between the contact regions and increased interfacial strength. [ABSTRACT FROM AUTHOR]

Coarse-grained molecular dynamics (CG-MD) simulations and subsequent persistent homology (PH) analysis were performed to correlate the structure and stress-strain behavior of polymer films. During uniaxial tensile MD simulations, the first principal component of the persistence diagram obtained by principal component analysis (PCA) was in good agreement with the stress-strain curve. This indicates that PH + PCA can identify critical ring structures relevant to the dynamic changes in MD simulations without requiring any prior knowledge. Inverse analysis of the persistence diagram revealed that smaller rings with ten or fewer CG beads mainly contribute to changes in the first principal component of the persistence diagram. This is due to the properties of the poly(ethylene oxide) chain, which favors the formation of a seven-membered helical structure during the self-entanglement process. The PH + PCA approach successfully reproduced the stress-strain curves for polymers with different nonbonding interactions and bond lengths. Moreover, the changes in the yield stress of each polymer film were qualitatively explained by the ring distribution in the persistence diagram. These results suggest that persistent homology analysis followed by PCA provides a versatile and powerful framework for correlating structural features with physical properties, such as ring distribution and stress-strain behavior in polymer films.

Background: Mercury intake is caused by eating seafood, such as tuna and other predatory fish species. To reduce the health risks of mercury intake, it is necessary to continuously measure and monitor mercury concentrations at fish farms and markets. We have developed a compact system that can detect multiple heavy metals by liquid asymmetric-electrode plasma optical emission spectroscopy (LAEP-OES)., Objective: The validity of the LAEP-OES method for total mercury levels was evaluated using standard solutions, certified substances, and specimens of bluefin tuna and other fish species., Methods: All specimens were dissolved in 4 M lithium hydroxide solution and then dispensed into a sample reservoir well of the single-use measurement reagent pack. Total mercury levels were automatically measured within 15 min of placement into the dedicated equipment. A total of 102 fish specimens, classified into 10 fish species, were evaluated using the new method and the results were compared to those obtained from validated analytical methods., Results: LOD (0.02 mg/kg), LOQ (0.07 mg/kg), repeatability (4.0%), intermediate precision (9.8%), and trueness (recoveries 107%) of the proposed method were within satisfactory limits for total mercury levels in fish. Additionally, when using various fish species, the method had a strong positive correlation with the results of cold-vapor atomic absorption spectrometry (CV-AAS, the official method) with Spearman rs = 0.984., Conclusion: The LAEP-OES method can be used for measuring total mercury levels in bluefin tuna. Total mercury measurement using this new method has the potential to be applied to other fish species., Highlights: Total mercury levels in fish were measured using our unique analysis system. Pacific bluefin tuna, southern bluefin tuna, and Atlantic bluefin tuna distributed in the Japanese market were analyzed for total mercury in their wild and farmed fish varieties., (© The Author(s) 2024. Published by Oxford University Press on behalf of AOAC INTERNATIONAL.)

Backgroud: In total hip arthroplasty (THA), the ideal stem length remains uncertain; different stem lengths are used in different cases or institutions. We aimed to compare the stress distributions of cementless tapered wedges and short stems in femurs with different femoral marrow geometries and determine the appropriate fit., Methods: Finite element models were created and analyzed using HyperMesh and LS-DYNA R11.1, respectively. The 3-dimensional shape data of the femurs were extracted from computed tomography images using the RETOMO software. Femurs were divided into 3 groups based on the Dorr classification. The computer-aided design data of cementless tapered wedge-type and short stems were used to select the appropriate size. In the finite element analysis, the loading condition of the femur was assumed to be walking. Volumes of interest (VOIs) were placed within the femur model at the internal and external contact points of the stem based on Gruen zones. The average stresses and strain energy density (SED) of the elements included in each VOI were obtained from the preoperative and postoperative models., Results: The von Mises stress and SED distributions of the cementless tapered wedge and short stems were similar in their respective Dorr classifications. In both stems, the von Mises stress and SED after THA were lower than before THA. The von Mises stress and SED of the cementless tapered wedge stem were higher than those of short stems. Cementless tapered wedge-type stems tended to have lower rates of change than short stems; however, Dorr C exhibited the opposite trend. In the Dorr classification comparison, the von Mises stress and SED were greater for both stems in the order of Dorr C > Dorr B > Dorr A, from Zone 2 to Zone 6., Conclusions: In Dorr A and B, the short stem exhibited a natural stress distribution closer to the preoperative femur than the tapered wedge stem; however, in Dorr C, the short stem may have a greater effect on stress distribution, suggesting that it may cause greater effects, such as fracture in the early postoperative period, than other Dorr types., Competing Interests: CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported., (Copyright © 2024 by The Korean Orthopaedic Association.)

This study proposes a novel long short-term memory (LSTM)-based model for predicting future physical properties based on partial data of molecular dynamics (MD) simulation. It extracts latent vectors from atomic coordinates of MD simulations using graph convolutional network, utilizes LSTM to learn temporal trends in latent vectors and make one-step-ahead predictions of physical properties through fully connected layers. Validating with MD simulations of Ni solid-liquid systems, the model achieved accurate one-step-ahead prediction for time variation of the potential energy during solidification and melting processes using residual connections. Recursive use of predicted values enabled long-term prediction from just the first 20 snapshots of the MD simulation. The prediction has captured the feature of potential energy bending at low temperatures, which represents completion of solidification, despite that the MD data in short time do not have such a bending characteristic. Remarkably, for long-time prediction over 900 ps, the computation time was reduced to 1/700th of a full MD simulation of the same duration. This approach has shown the potential to significantly reduce computational cost for prediction of physical properties by efficiently utilizing the data of MD simulation., (Creative Commons Attribution license.)

The S -methylation/intramolecular cyclization of γ-sulfanylamide is depicted. Different methylating reagents were successfully employed for S -methylation, depending on the substituent pattern of the amide in the starting γ-sulfanylamides; trimethyloxonium tetrafluoroborate was used for N -aryl substituted γ-sulfanylamides, and the combination of methyl iodide and silver(I) tetrafluoroborate was used for N -alkyl substituted γ-sulfanylamides. When the resulting sulfonium salt was treated with DBU, it smoothly underwent intramolecular cyclization to produce a series of N -aryl, N -alkyl, N,N -dialkyl or N -alkyl- N -aryl substituted 5-amino-3(2 H )-furanones in 55%-quantitative yields.

Introduction: COVID-19 may be associated with orthopedic symptoms, including myalgia and joint pain. There are reports of reactive arthritis and acute arthritis diagnosed after COVID-19; however, COVID-19-associated pyogenic arthritis has not been reported., Case Report: We treated a young woman with secondary pyogenic hip arthritis that started after COVID-19. The patient was a 23-year-old woman who developed acute pain in the right hip 9 days after being diagnosed with COVID-19. Blood cultures revealed methicillin-sensitive Staphylococcus aureus and contrast-enhanced computed tomography revealed joint effusion in the right hip. Although the joint fluid culture results were negative, we suspected pyogenic arthritis of the hip joint and performed curettage and continuous irrigation of the right hip joint. Intraoperative histopathological examination of the synovial membrane revealed numerous neutrophils with segmental nuclei, consistent with a diagnosis of pyogenic arthritis., Conclusion: To the best of our knowledge, this is the first report of probable secondary pyogenic hip arthritis in a patient with COVID-19., Competing Interests: Conflict of Interest: Nil, (Copyright: © Indian Orthopaedic Research Group.)

In the realm of materials science, the integration of machine learning techniques has ushered in a transformative era. This study delves into the innovative application of generative adversarial networks (GANs) for generating heat flux data, a pivotal step in predicting lattice thermal conductivity within metallic materials. Leveraging GANs, this research explores the generation of meaningful heat flux data, which has a high degree of similarity with that calculated by molecular dynamics simulations. This study demonstrates the potential of artificial intelligence (AI) in understanding the complex physical meaning of data in materials science. By harnessing the power of such AI to generate data that is previously attainable only through experiments or simulations, new opportunities arise for exploring and predicting properties of materials., (Creative Commons Attribution license.)

Introduction: Unilateral subchondral insufficiency fractures (SIF) of the femoral head have been reported in many cases; however, bilateral cases occurring simultaneously are very rare., Case Report: We report two cases of relatively active elderly females (aged 73 and 67 years), in which bilateral hip pain appeared simultaneously without any specific triggers. There were no notable lifestyle or medication histories. Imaging and histopathology of the bone excised surgically supported the diagnosis. In Case 1, there was a decrease in bone mineral density and poor congruency between the femoral head and acetabulum. In Case 2, the posterior tilt of the pelvis with aging decreased coverage of the femoral head, and the poor congruency between the femoral head and acetabulum was thought to have contributed to uneven distribution and increased stress in the loading zone., Conclusion: We encountered two unusual cases with contemporaneous bilateral SIF in the elderly. In recent years, the number of highly active elderly people has increased with the increase in healthy life expectancy. The combined effect of factors such as bone fragility, posterior pelvic tilt, and high activity level likely caused bilateral SIFs, and we should be careful as we expect to see an increase in such cases in the future., Competing Interests: Conflict of Interest: Nil, (Copyright: © Indian Orthopaedic Research Group.)

Adsorption energies of additive molecules in paint materials on the iron oxide substrate are investigated by molecular dynamics (MD) simulations to find the key feature of adhesion, which is one of the indispensable elements for the corrosion resistance of coated materials. Both edge-on and face-on adsorptions are observed for most additive molecules such as phenylsuccinic acid and benzoic acid. On the other hand, only the edge-on adsorption is observed for the specific molecule having a benzothiazole ring due to the effect of steric conformation. The largest adsorption energy per functional group is observed for two nitrogen atoms in the thiazole ring and amino group, which influences the relationship between face-on and edge-on adsorption energies. Moreover, a correlation analysis using RDKit descriptors is performed to discuss the dominant factor for the adsorption energy of additive molecules. The descriptor for the magnitude of partial charge relative to the molecular surface area and the one for the topological polar surface area have the largest correlation with the adsorption energy of the target molecules. It is significant in this study to extract key factors that contribute to molecular adhesion through MD simulations in combination with correlation analysis using RDKit descriptors. This study is a good example of the computer-assisted design of new paint materials., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Background: This study aimed to clarify the characteristics of stress distribution caused by the placement of tapered wedge stems in bowed femurs compared with that in normal femurs and the effect of varus stem placement., Methods: Models with normal and enhanced bowing were created from the right-side computed tomography data of a 17-year-old woman with the least bowing among 40 participants who underwent anterior cruciate ligament reconstruction or operative treatment for trauma in our hospital between January 2017 and May 2018. Finite element analysis was performed, assuming the tapered wedge stem was placed in the neutral and varus positions., Results: Varus stem placement on a femur with normal bowing showed a deviation and increase of von Mises stresses in the medial femur. Stem placement on a bowed femur, even when placed in the neutral position, increased stress across the periprosthetic bone. When the stem was placed in the varus position, von Mises stress across the periprosthetic bone increased. Zone 7, with strong bowing, demonstrated 3.6-fold increased stress compared with normal femurs. The maximum tensile principal stress was greatest in zone 6 and increased in zones 3 and 4., Conclusions: Surgeons should assess femoral bowing preoperatively and pay particular attention to intraoperative stem alignment for femurs with high bowing., Competing Interests: CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported., (Copyright © 2023 by The Korean Orthopaedic Association.)

Background: Only few studies have been conducted on leg length discrepancy (LLD) in patients with hip osteoarthritis (OA). This study aimed to examine the relationship between perceived LLD (pLLD) and structural LLD (sLLD) in patients with advanced OA and to determine the factors influencing both LLDs. This retrospective study aimed to answer the following questions: (1) are older adults less likely to perceive LLD than younger adults? (2) is there a relationship between pLLD and sLLD? and (3) is pLLD associated with patient satisfaction?, Hypothesis: We hypothesized that older adults are less likely to perceive LLD than younger adults., Patients and Methods: We recruited 125 patients (102 women and 23 men) with hip OA associated with developmental dysplasia of the hip defined as grade 3 or higher according to the Tönnis classification and excluding contralateral grade 2 or higher. The mean age of the patients was 65.2±11.2 (36-85) years. Before surgery, 2-mm and 5-mm thick plates were placed on the floor on the plantar surface of the short leg to measure pLLD. Preoperative computed tomography (CT) was performed and sLLDs were measured using the 3D planning software ZedHip. The following associated factors were evaluated: age, height, weight, body mass index (BMI), adduction and abduction range of motion (ROM) of the affected hip joint, Crowe classification, standing pelvic inclination in the coronal plane, Cobb angle and Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ)., Results: The absolute difference between pLLD and sLLD was modestly positively correlated with age (R=0.206; p<0.05) indicating older patients were less prone to perceive LLD. A strong positive correlation was found between pLLD (4.8±7.3mm; range: -37 to 28mm) and sLLD (6.4±7.0mm; range: -29.9 to 23.7mm) (R=0.714, p<0.05). The greater the pLLD, the smaller the hip abduction ROM (24.8±11.6°; range: 0 to 45°) tended to be, while the greater the sLLD, the smaller the hip abduction and adduction ROM (10.3±5.7°; range: 0 to 25°) tended to be (R= -0.259 and R= -0.297, respectively; p<0.05) The clinical significance of this finding is that pLLD may be improved if hip ROM training is performed before surgery. pLLD was significantly smaller in the group without pelvic inclination (8.0±14.1mm; range: -37 to 22mm) than in the group with pelvic inclination to the affected side (6.9±7.5mm; range: -12 to 28mm) and in the group with no inclination to the affected side (7.3±7.6mm; range: -8 to 25mm) (p<0.05) The clinical significance of this finding is that improving pelvic inclination with hip ROM training or muscle stretching may also reduce pLLD. No significant differences were noted between pLLD and JHEQ total scores or subgroups., Discussion: Older patients had less pLLD. Preoperative pLLD was strongly correlated with sLLD but not with patient satisfaction. These results may be useful for conservative treatment of OA, preoperative planning and intraoperative leg length correction., Level of Evidence: IV; case control study., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

Background: Whether femoral bowing or its direction has a mechanical effect on the proximal femur is unclear. This study aimed to define the changes in stress distribution in the proximal femur associated with femoral bowing using finite element analysis., Methods: We created four femoral models: original, entire lateral bowing, entire anterior bowing, and the middle of both (50% anterolateral bowing) from computed tomography data of women with standard bowing. Each model's stress distribution was compared by two-layering the stress distribution under loading conditions during walking. We also evaluated displacement vectors., Results: In all directions of femoral bowing, the stress increased in the femoral neck and the femoral trochanter in the 50% anterolateral bowing. The direction of deformation of the vector for the femoral head increased anteroinferiorly in the 50% anterolateral bowing., Conclusions: This study showed that the stress distribution at the proximal femur shifted laterally. The high-stress area increased at the femoral neck or trochanter due to increasing femoral bowing. Femoral bowing also increases the anteroinferior vector in the femoral head. This study provides valuable insights into the mechanism of proximal femoral fractures in older adults., (© 2023. The Author(s).)

Robust underwater adhesion is challenging because a hydration layer impedes the interaction between substrates and adhesives. Phenolic adhesives inspired by marine creatures such as mussels were extensively studied, but these adhesives have not reached the adhesion strength and substrate diversity of Man-made dry adhesives. Here, we report a class of ultrastrong underwater adhesives with molecular phenolic designs extending beyond what nature has produced. These non-canonical phenolic polymers show versatile adhesion on various materials, with adhesion strengths exceeding 10 MPa on metal. Incorporating even just a small amount (<10%) of non-canonical phenolic groups into a polymer is sufficient for dramatically enhancing underwater adhesion, suggesting that this new class of phenolic materials will be incorporated into various industrial polymer systems in the future., (© 2022. The Author(s).)

The microscopic origins of the activity and selectivity of electrocatalysts has been a long-lasting enigma since the 19th century. By applying an active-data-mining approach, employing a mean-field kinetic model and a statistical approach of Bayesian data assimilation, we demonstrate here a fast decoding to extract key properties in the kinetics of complicated electrode processes from current-potential profiles in experimental and literary data. As the proof-of-concept, kinetic parameters on the four-electron oxygen reduction reaction in the 0.1 M HClO 4 solution (ORR: O 2 + 4 e - + 4H + → 2H 2 O) of various platinum-based single-crystal electrocatalysts are extracted from our own experiments and third-party literature to investigate the microscopic electrode processes. Furthermore, data assimilation of the mean-field ORR model and experimental data is performed based on Bayesian inference for the inductive estimation of kinetic parameters, which sheds light on the dynamic behavior of kinetic parameters with respect to overpotential. This work shows that a fast-decoding algorithm based on a mean-field kinetic model and Bayesian data assimilation is a promising data-driven approach to extract key microscopic features of complicated electrode processes and therefore will be an important method toward building up advanced human-machine collaborations for the efficient search and discovery of high-performance electrochemical materials.

The very early nucleation stage of a transition metal dichalcogenide (TMD) was directly observed with in-situ monitoring of chemical vapor deposition and automated image analysis. Unique nucleation dynamics, such as very large critical nuclei and slow to rapid growth transitions, were observed during the vapor-liquid-solid (VLS) growth of monolayer tungsten disulfide (WS 2 ). This can be explained by two-step nucleation, also known as non-classical nucleation, in which metastable clusters are formed through the aggregation of droplets. Subsequently, nucleation of solid WS 2 takes place inside the metastable cluster. Furthermore, the detailed nucleation dynamics was systematically investigated from a thermodynamic point of view, revealing that the incubation time of metastable cluster formation follows the traditional time-temperature transformation diagram. Quantitative phase field simulation, combined with Bayesian inference, was conducted to extract quantitative information on the growth dynamics and crystal anisotropy from in-situ images. A clear transition in growth dynamics and crystal anisotropy between the slow and rapid growth phases was quantitatively verified. This observation supports the existence of two-step nucleation in the VLS growth of WS 2 . Such detailed understanding of TMD nucleation dynamics can be useful for achieving perfect structure control of TMDs., (© 2021. The Author(s).)

Initial cap formation is an important process of carbon nanotube (CNT) growth where a hexagonal carbon network is lifted off from the catalyst surface. In this study, free energy surface (FES) of initial cap formation in the CNT growth is investigated by metadynamics simulation. A two-dimensional collective variable (CV) space is newly developed to examine the complicated formation process of the cap structure, which consists of the formation of a hexagonal carbon network and lift-off of the network from the catalyst surface. States before and after the lift-off of the carbon network are clearly distinguished in the two-dimensional FES. Therefore, free energy difference before and after the lift-off can be directly derived from the two-dimensional FES. It was revealed that the cap structure is stable at a high temperature due to the entropy effect, while the carbon network covering the catalyst surface is energetically stable. The new insight in this study is achieved owing to metadynamics simulation in conjunction with a newly developed two-dimensional CV space since it is impossible to explore FES for such complicated processes in the framework of conventional molecular dynamics simulation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Temperature dependence of solid-liquid interfacial properties during crystal growth in nickel was investigated by ensemble Kalman filter (EnKF)-based data assimilation, in which the phase-field simulation was combined with atomic configurations of molecular dynamics (MD) simulation. Negative temperature dependence was found in the solid-liquid interfacial energy, the kinetic coefficient, and their anisotropy parameters from simultaneous estimation of four parameters. On the other hand, it is difficult to obtain a concrete value for the anisotropy parameter of solid-liquid interfacial energy since this factor is less influential for the MD simulation of crystal growth at high undercooling temperatures. The present study is significant in shedding light on the high potential of Bayesian data assimilation as a novel methodology of parameter estimation of practical materials an out of equilibrium condition.

Atomistic simulation methods for the quantification of free energies are in wide use. These methods operate by sampling the probability density of a system along a small set of suitable collective variables (CVs), which is, in turn, expressed in the form of a free energy surface (FES). This definition of the FES can capture the relative stability of metastable states but not that of the transition state because the barrier height is not invariant to the choice of CVs. Free energy barriers therefore cannot be consistently computed from the FES. Here, we present a simple approach to calculate the gauge correction necessary to eliminate this inconsistency. Using our procedure, the standard FES as well as its gauge-corrected counterpart can be obtained by reweighing the same simulated trajectory at little additional cost. We apply the method to a number of systems-a particle solvated in a Lennard-Jones fluid, a Diels-Alder reaction, and crystallization of liquid sodium-to demonstrate its ability to produce consistent free energy barriers that correctly capture the kinetics of chemical or physical transformations, and discuss the additional demands it puts on the chosen CVs. Because the FES can be converged at relatively short (sub-ns) time scales, a free energy-based description of reaction kinetics is a particularly attractive option to study chemical processes at more expensive quantum mechanical levels of theory.

Solid-liquid interfacial properties out of equilibrium provide the essential information required for understanding and controlling solidification microstructures in metallic materials. However, few studies have attempted to reveal all interfacial properties out of equilibrium in detail. The present study proposes an approach for simultaneously estimating all interfacial properties in a pure metal below the melting point on the basis of the Bayesian inference theory. The solid-liquid interfacial energy, interfacial mobility, and anisotropy parameters in pure Fe are estimated by combining molecular dynamics simulation with phase-field simulation using an ensemble Kalman filter, which is a data assimilation technique. Furthermore, the temperature dependences of all interfacial parameters are computed and discussed. In summary, the proposed multiscale approach integrates atomistic and microstructural simulations within the framework of data science and it has considerable potential for a wide variety of applications in materials engineering.

Chirality-selective synthesis of single-walled carbon nanotubes (SWNTs) has been a research goal for the last two decades and is still challenging due to the difficulty in controlling the atomic structure in the one-dimensional material. Here, we develop an optimized approach for controlling the chirality of species by tuning the oxidation degree of Co catalyst. Predominant synthesis of (6,4) SWNTs is realized for the first time. The detailed mechanism is investigated through a systematic experimental study combined with first-principles calculations, revealing that the independent control of tube diameter and chiral angle achieved by changing the binding energy between SWNTs (cap and tube edge) and catalyst causes a drastic transition of chirality of SWNTs from (6,5) to (6,4). Since our approach of independently controlling the diameter and chiral angle can be applied to other chirality species, our results can be useful in achieving the on-demand synthesis of specific-chirality SWNTs.

A variational formulation of a quantitative phase-field model is presented for nonisothermal solidification in a multicomponent alloy with two-sided asymmetric diffusion. The essential ingredient of this formulation is that the diffusion fluxes for conserved variables in both the liquid and solid are separately derived from functional derivatives of the total entropy and then these fluxes are related to each other on the basis of the local equilibrium conditions. In the present formulation, the cross-coupling terms between the phase-field and conserved variables naturally arise in the phase-field equation and diffusion equations, one of which corresponds to the antitrapping current, the phenomenological correction term in early nonvariational models. In addition, this formulation results in diffusivities of tensor form inside the interface. Asymptotic analysis demonstrates that this model can exactly reproduce the free-boundary problem in the thin-interface limit. The present model is widely applicable because approximations and simplifications are not formally introduced into the bulk's free energy densities and because off-diagonal elements of the diffusivity matrix are explicitly taken into account. Furthermore, we propose a nonvariational form of the present model to achieve high numerical performance. A numerical test of the nonvariational model is carried out for nonisothermal solidification in a binary alloy. It shows fast convergence of the results with decreasing interface thickness.

Hydration reactions on a carbonate-terminated cubic ZrO 2 (110) surface were analyzed using ab initio molecular dynamics (AIMD) simulations. After hydration reactions, carbonates were still present on the surface at 500 K. However, these carbonates are very weak conjugate bases and only act as steric hindrance in proton hopping processes between acidic chemisorbed H 2 O molecules (Zr-OH 2 ) and monodentate hydroxyl groups (Zr-OH - ). Similar to a carbonate-free hydrated surface, Zr-OH 2 , Zr-OH - , and polydentate hydroxyl groups ([double bond splayed left]OH + ) were observed, while the ratio of acidic Zr-OH 2 was significantly larger than that on the carbonate-free hydrated surface. A thermodynamic discussion and bond property analysis reveal that CO 2 adsorption significantly decreases the basicity of surface oxide ions ([double bond splayed left]O), whereas the acidity of Zr-OH 2 is not affected. As a result, protons released from [double bond splayed left]OH + react with Zr-OH - to form Zr-OH 2 , leading to a deficiency of proton acceptor sites, which decreases the proton conductivity by the hopping mechanism.

Can completely homogeneous nucleation occur? Large scale molecular dynamics simulations performed on a graphics-processing-unit rich supercomputer can shed light on this long-standing issue. Here, a billion-atom molecular dynamics simulation of homogeneous nucleation from an undercooled iron melt reveals that some satellite-like small grains surrounding previously formed large grains exist in the middle of the nucleation process, which are not distributed uniformly. At the same time, grains with a twin boundary are formed by heterogeneous nucleation from the surface of the previously formed grains. The local heterogeneity in the distribution of grains is caused by the local accumulation of the icosahedral structure in the undercooled melt near the previously formed grains. This insight is mainly attributable to the multi-graphics processing unit parallel computation combined with the rapid progress in high-performance computational environments.Nucleation is a fundamental physical process, however it is a long-standing issue whether completely homogeneous nucleation can occur. Here the authors reveal, via a billion-atom molecular dynamics simulation, that local heterogeneity exists during homogeneous nucleation in an undercooled iron melt.

Adding a mechanical degree of freedom to the electrical and optical properties of atomically thin materials can provide an excellent platform to investigate various optoelectrical physics and devices with mechanical motion interaction. The large scale fabrication of such atomically thin materials with suspended structures remains a challenge. Here we demonstrate the wafer-scale bottom-up synthesis of suspended graphene nanoribbon arrays (over 1,000,000 graphene nanoribbons in 2 × 2 cm(2) substrate) with a very high yield (over 98%). Polarized Raman measurements reveal graphene nanoribbons in the array can have relatively uniform-edge structures with near zigzag orientation dominant. A promising growth model of suspended graphene nanoribbons is also established through a comprehensive study that combined experiments, molecular dynamics simulations and theoretical calculations with a phase-diagram analysis. We believe that our results can contribute to pushing the study of graphene nanoribbons into a new stage related to the optoelectrical physics and industrial applications.

The atomistic mechanism of dissociative adsorption of ethylene molecules on a Ni cluster is investigated by ab initio molecular-dynamics simulations. The activation free energy to dehydrogenate an ethylene molecule on the Ni cluster and the corresponding reaction rate is estimated. A remarkable finding is that the adsorption energy of ethylene molecules on the Ni cluster is considerably larger than the activation free energy, which explains why the actual reaction rate is faster than the value estimated based on only the activation free energy. It is also found from the dynamic simulations that hydrogen molecules and an ethane molecule are formed from the dissociated hydrogen atoms, whereas some exist as single atoms on the surface or in the interior of the Ni cluster. On the other hand, the dissociation of the C-C bonds of ethylene molecules is not observed. On the basis of these simulation results, the nature of the initial stage of carbon nanotube growth is discussed.