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The February 2024 issue of the Journal of Materials Science features a cover paper titled "Enhancing the impact property of high-entropy alloys with graphene layers: a molecular dynamics study" by Qing-Xiang Pei et al. The paper explores the use of molecular dynamics simulations to study the impact of a projectile on a high-entropy alloy (HEA) containing layers of graphene. The authors highlight the broad interest in their research, as it appeals not only to the modeling community but also to other communities interested in the materials being modeled. The paper provides valuable insights into the behavior of composite materials and includes figures illustrating the preparation of the model material and the interaction between a projectile and the HEA. The article is freely accessible through the SharedIt link provided, and the corresponding authors can be contacted for access to the data. The publisher, Springer Nature, maintains a neutral stance on jurisdictional claims and institutional affiliations. [Extracted from the article]

Phagraphene is a newly proposed two-dimensional allotrope of carbon. Its structure resembles that of a defective graphene sheet. The unit cell structure of phagraphene consists of a 5–6–7 ring sequence due to which it possesses lower energy than most carbon allotropes. Phagraphene has properties, namely thermal conductivity of 218 ± 20 W/mK and 285 ± 29 W/mK, along armchair and zigzag directions, respectively, a tensile strength of 85 ± 2 GPa, the elastic modulus of 870 ± 15 GPa along armchair and 800 ± 14 GPa along zigzag direction, and fracture strain of the same order as that of pristine graphene. Density functional theory and molecular dynamics simulations have proved the unique electronic properties of phagraphene, namely direction-dependent Dirac cones, tunable Fermi velocities, quasi-direct band gap, to be comparable with pristine graphene. Based on molecular dynamics and density functional theory investigations, phagraphene is capable of being used in Li-based batteries and thermoelectric devices as anode material due to its good adsorption properties and remarkably good doping characteristics. Such characteristics can lead to a future trend of analyzing such allotropes because phagraphene can provide potential applications in atmospheric pollutant-detecting and drug-carrying properties in ailments like cancer. This paper is a nascent one discussing all the previous works on molecular dynamics simulations of phagraphene and tries to serve as the leading one for researchers interested in this field. This paper summarizes the mechanical and thermal properties of phagraphene estimated using molecular dynamics simulations as studied in previous works. The study shows that molecular dynamics has a good application in studying such a novel carbon allotrope. The discussions made in this paper thematize phagraphene's properties as a next-generation material and can help the researchers in a qualitative overview. [ABSTRACT FROM AUTHOR]

A cross-scale analysis method for predicting the compressive mechanical properties of tin-based bearing alloy was proposed based on microstructure finite element simulation and molecular dynamics (MD) simulation. The actual metallographic microstructure of tin-based bearing alloy taken by optical microscopy was utilized to construct the representative volume element (RVE) model for the computational modeling. The compression stress–strain curves of β-Sn and Cu6Sn5 obtained by MD simulation were used as the input material property parameters of each constituent phase in RVE model for the microstructure finite element analysis. The compression simulation was carried out for the tin-based bearing alloy with the microstructure containing Sn matrix and Cu6Sn5 phase. The results show that the simulation analysis method can predict the compression strength and elasticity of the studied tin-based bearing alloy well by comparing the simulated results with the experimentally obtained data. It is hoped that this paper can provide a simulation method for realizing the prediction of the mechanical properties based on microstructure and revealing the microscope mechanism of materials, thus providing theoretical guidance for the micro-design of high-performance tin-based bearing alloy. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms behind sintering Cu-Ag core–shell nanoparticles can help us optimize the sintering process parameters and design the core–shell structure to achieve the desired sintering structure. In this paper, we employed molecular dynamics simulations to investigate the sintering behaviors and mechanisms of CS NPs, taking into account the effects of shell thickness, particle size, and temperature. Our results revealed that dislocation loops in Cu-Ag CS NPs played a crucial role in sintering by emitting dislocations that facilitated crystal evolution, thereby reducing the number of amorphous structures. The state of dislocation loops could be controlled by shell thickness and NP size. As the shell thickness decreased to 0.5 nm, the structure of the dislocation loops could not be generated due to the extremely chaotic and thin Ag atoms. Furthermore, for NPs of the same size, the CS NP with a 0.5-nm shell thickness was the most active. Despite the neck not consisting of a Cu core, the Cu core, particularly its interface, could still participate in the sintering process. At 900 K, limited interface diffusion could be activated. [ABSTRACT FROM AUTHOR]

The impact of solute Al on the penetration of Cu atoms into the Fe grain boundary (GB) in the Fe–Cu embrittlement system was investigated by performing molecular dynamics simulations. Furthermore, the first principle density functional theory calculation was also employed to determine the binding properties and the electronic structure of GBs doped with solute atoms. The inhibition mechanism of liquid metal embrittlement (LME) cracks in the Fe–Cu system by Al was analyzed at the atomic scale by conducting simulations and calculations. The results show that the diffusion rate of Al along with the GB direction was much higher than that of Cu, and the preferential penetration and segregation of Al atoms acted as a barrier layer. Moreover, the addition of Al reduced the potential energy of Cu atoms, thus stabilizing their motion. These factors significantly inhibited the diffusion of Cu atoms along with the GB direction. The binding property of Fe GB doped with a high concentration of Cu was severely deteriorated, while the Al doping improved the atomic bonding. GBs with higher binding properties are less susceptible to fracture and groove under the application of tensile stress. This paper presents a novel perspective on the inhibition mechanism of LME cracks by doping a third component to inhibit the penetration of embrittlement atoms. [ABSTRACT FROM AUTHOR]

Lamellar heterostructures containing gallium nitride (GaN) have excellent photoelectric properties and also play an important role in lighting, the quantum field, and other fields. Exploring the nanoscale processing of lamellar heterostructure GaN is crucial to the manufacturing of high-performance devices based on heterostructure GaN. In this paper, the microstructure, surface morphology, dislocation length, Von Mises stress, temperature, number of removed atoms, and surface roughness of lamellar heterostructure GaN were systematically investigated using molecular dynamics simulation. The results show the presence of a large number of phase transitions, dislocation growth, and stress during nanogrinding; moreover, temperature also increases during this process. Furthermore, increasing the grinding speed will inhibit dislocation growth; increasing the grinding depth will cause extensive damage to the material surface. Therefore, this study presents a theoretical basis for the processing of lamellar heterostructure GaN. [ABSTRACT FROM AUTHOR]

In this paper, the initiation of interfacial damage in SnPb alloy was investigated at the atomic scale through molecular dynamics simulations. The focus was primarily on the structural stability of the Sn/Pb interface with different orientations, the formation energies of vacancies in different Sn/Pb interfaces, and the short-range interactions between dislocations and the Sn/Pb interface. The results revealed a correlation between the interfacial energies of all four Sn/Pb interfaces and the disorder of Sn and Pb atoms near the interface, where a more regular atomic arrangement resulted in lower interfacial energy. The vacancy formation energies near the Sn/Pb interfaces varied depending on the interface type, although all types contributed to reducing these energies. Furthermore, the Sn/Pb interface acts as a barrier to dislocations in both Pb and β-Sn phases, while leading to the cross-slip of screw dislocations in the Pb phase. Edge dislocations in the β-Sn phase induce significant strain localization at the interface, initiating interfacial damage and crack nucleation. These findings are highly significant for understanding damage mechanisms in SnPb alloy and advancing high-performance solder development. [ABSTRACT FROM AUTHOR]

Numerous catalysts have been studied and developed to catalyze the decomposition of methane and in this paper, an iron slab is selected as the catalyst to obtain stable Fe3C and C2 during the decomposition of methane. We combine ReaxFF MD simulations and laboratory work to investigate methane decomposition and carburization of carbon atoms. The analysis of XRD and TEM confirms the Fe3C formed after the reaction and demonstrates its microscopic morphology. Simulations reveal that the iron slab accelerates the primary decomposition of CH4 in the meantime promotes the synthesis of hydrogen molecules and the whole carburizing reaction mechanism has been characterized by the formation of Fe3C and diffusion of C atoms which has been described with carburizing depth. Finally, the influence of methane concentration is explored and the result shows that an appropriate enhancement accelerates the carburizing reaction while the excessive increase will inhibit it. [ABSTRACT FROM AUTHOR]

The demolding process of electroforming technology in fabricating microstructured optical-functional thin films produces the problem of excessive bonding between the metal substrate and the metal replica, which triggers the deformation of the microstructure and the reduction of precision, and the deposition of Cr–O–C discrete nuclei at the interface can play a good role in assisting the demolding effect. In this paper, the tensile deformation of polycrystalline Cu/Ni and Cu/Cr–O–C/Ni composites is investigated using molecular dynamics methods. The results show that the Cu/Ni model produces a large number of HCP structures during stretching, with holes at the interface and a large number of Cu atoms transferring to the Ni layer. The addition of the Cr–O–C layer reduces the yield strength of the Cu/Cr–O–C/Ni model by 26.41%, and at the same time, the dislocation proliferation at the interface is reduced, and the fracture is at the centralized interface, and the fracture time is reduced by 90.8%. The higher number of Cr–O–C atoms at the interface decreases the transfer of Cu atoms to the Ni layer. The results provide a possible explanation for the Cr–O–C layer-assisted precision electrodeposition debonding. [ABSTRACT FROM AUTHOR]

Modifying epoxy resin with carbon nanomaterials is one of the promising methods to improve the fiber-reinforced polymer (FRP)/concrete interfacial properties, and such manipulation first requires comprehensive understanding of the bonding mechanism between the modified epoxy resin and the concrete matrix. In this paper, the interfacial bonding properties between epoxy resins modified by graphene oxide (GO) nanosheets and calcium silicate hydrate (C–S–H), the main bulk phase of concrete, are investigated using molecular dynamics simulation. At the molecular level, the GO-epoxy/C–S–H interface is constructed, and the mechanical behaviors of the interfacial system are simulated at elevated temperatures (from 298.15 to 433.15 K). Results show that the GO modification significantly enhances the mechanical resistance of the epoxy/C–S–H interface, as evidenced by the increase in the pulling force threshold of ~ 20%. Analysis reveals that the polar groups on the GO surface strengthen the interfacial ionic and structural hydrogen bonds, thus improving the bonding integrity of the epoxy/C–S–H interface. At elevated temperature levels, the high thermal stability of the GO-epoxy molecule, as well as its low energy loss with the C–S–H matrix, is the main driver for the enhanced thermal and mechanical properties of the epoxy/C–S–H interface. [ABSTRACT FROM AUTHOR]

The deterioration of cement-basted materials serviced in leaching environments is strongly dependent on the decalcification behavior of calcium silicate hydrates after complete dissolution of calcium hydroxide. This paper examines the deteriorating condition of calcium silicate hydrates (hereinafter referred to C–S–H(I)) samples with the decalcification degree which is controlled by immersing samples into leaching solutions with different NH4Cl concentrations. The composition, chemical structure, micromorphology and pore structure of un-leached and leached C–S–H(I) samples were determined using XRD, TG, FTIR, 29Si NMR, SEM, TEM and N2 adsorption–desorption measurements. Results reveal that the decalcification degree of C–S–H(I) samples increases with the increasing NH4Cl concentration with the Ca/Si atomic ratio decreasing from 0.91 to 0.02. The area of flocculent micromorphology of C–S–H(I) samples increases with the decalcification degree due to the continuous generation of cross-linking C–S–H(I) and amorphous silica gel. In addition, the decalcification behavior damages the crystallinity, coarsens the pore structure and decreases the chemically-bound water content of C–S–H(I) samples. Molecular dynamics simulations prove that increasing NH4Cl content results in weaker connectivity stability and more breakage of Ca–O bond in C–S–H(I) molecules. [ABSTRACT FROM AUTHOR]

Mo/Cu composites exhibit significant potential for applications in electronic packaging and other domains. However, the diffusion process and mechanism of Mo/Cu composites are difficult to experiment with. Therefore, in this paper, a new potential function is first constructed and verified for the Mo/Cu system. The Mo/Cu diffusion process is studied on the atomic scale by molecular dynamics (MD) simulation. The conditions for rapid diffusion of Mo/Cu are determined at 1000 K and Mo (100) interface orientation. The vacancy diffusion mechanism in the Mo/Cu system is elucidated through the analysis of the diffusion results. Finally, the diffusion under an external electric field is simulated, and the critical condition for diffusion is determined by increasing the vacancy concentration. The diffusion temperature can be reduced by about 100 K at E = 0.002 V/Å. This study can provide theoretical support for the electro-assisted preparation of Mo/Cu composites.Graphical abstract: Mo/Cu composites exhibit significant potential for applications in electronic packaging and other domains. However, the diffusion process and mechanism of Mo/Cu composites are difficult to experiment with. Therefore, in this paper, a new potential function is first constructed and verified for the Mo/Cu system. The Mo/Cu diffusion process is studied on the atomic scale by molecular dynamics (MD) simulation. The conditions for rapid diffusion of Mo/Cu are determined at 1000 K and Mo (100) interface orientation. The vacancy diffusion mechanism in the Mo/Cu system is elucidated through the analysis of the diffusion results. Finally, the diffusion under an external electric field is simulated, and the critical condition for diffusion is determined by increasing the vacancy concentration. The diffusion temperature can be reduced by about 100 K at E = 0.002 V/Å. This study can provide theoretical support for the electro-assisted preparation of Mo/Cu composites. [ABSTRACT FROM AUTHOR]

In this paper, molecular dynamics simulations are used to study the effects of temperature on the transport of chloride and sulfate in the nanopores of aluminum-doped cement-based materials (i.e., CASH gels) exposed to aqueous solutions of NaCl and Na2SO4 at 283, 293, 303, 333, and 363 K. It is shown that high temperatures increase the initial transport rates of water molecules and ions while weakening the hydration layer around ions. This increases the probability of ion–ion and ion–substrate contact and thus makes ions more likely to cluster in solution and be captured by the substrate. Both cluster formation and substrate capture can significantly restrict the free movement of ions in solution and thus gradually reduce the ion transport rate. In addition, since sulfate ions have four oxygen atoms that can capture other ions, large ion clusters form more readily in Na2SO4 solution than in NaCl solution. The capture of these large ion clusters at the interface can cause a "necking" phenomenon that hinders the subsequent transport of water molecules and ions into the nanopore. These results provide a nanoscale basis for designing aluminum-doped cement-based materials with enhanced durability at high temperatures. [ABSTRACT FROM AUTHOR]

Lattice rotation mechanism plays an important role in the plastic deformation and the microstructure evolution of nanocrystalline metals. It assists the grain growth and the polycrystal texture formation. In this paper, the lattice rotation of quasi-3D Ni samples under uniaxial tension is investigated by molecular dynamics simulations. For this purpose, the bi-crystal and polycrystal models are created and systematic molecular dynamics simulations are carried out to mimic the uniaxial tensile tests. Based on the Schmid shear slip theory, the relationship between the Schmid factor of different slip systems and the grain orientation angle is established. It is found that the starting slip system angle is a fixed angle with the initial orientation angle of grain. Moreover, the cumulative rotation of the grain slip system and the initial angle of the slip system are statistically analyzed. It is found that a larger deflection angle of the slip system leads to a larger lattice rotation. [ABSTRACT FROM AUTHOR]

A micro-molecule of dimension 125 nm has caused around 479 million human infections (80 M for the USA) and 6.1 million human deaths (977,000 for the USA) worldwide and slashed the global economy by US$ 8.5 Trillion over two years period. The only other events in recent history that caused comparative human life loss through direct usage (either by human or nature, respectively) of structure-property relations of 'nano-structures' (either human-made or nature, respectively) were nuclear bomb attacks during World War II and 1918 Flu Pandemic. This molecule is called SARS-CoV-2, which causes a disease known as COVID-19. The high liability cost of the pandemic had incentivized various private, government, and academic entities to work towards finding a cure for this and emerging diseases. As an outcome, multiple vaccine candidates are discovered to avoid the infection in the first place. But so far, there has been no success in finding fully effective therapeutic candidates. In this paper, we attempted to provide multiple therapy candidates based upon a sophisticated multi-scale in-silico framework, which increases the probability of the candidates surviving an in-vivo trial. We have selected a group of ligands from the ZINC database based upon previously partially successful candidates, i.e., Hydroxychloroquine, Lopinavir, Remdesivir, Ritonavir. We have used the following robust framework to screen the ligands; Step-I: high throughput molecular docking, Step-II: molecular dynamics analysis, Step-III: density functional theory analysis. In total, we have analyzed 242,000(ligands)*9(proteins) = 2.178 million unique protein binding site/ligand combinations. The proteins were selected based on recent experimental studies evaluating potential inhibitor binding sites. Step-I had filtered that number down to 10 ligands/protein based on molecular docking binding energy, further screening down to 2 ligands/protein based on drug-likeness analysis. Additionally, these two ligands per protein were analyzed in Step-II with a molecular dynamic modeling-based RMSD filter of less than 1Å. It finally suggested three ligands (ZINC001176619532, ZINC000517580540, ZINC000952855827) attacking different binding sites of the same protein(7BV2), which were further analyzed in Step-III to find the rationale behind comparatively higher ligand efficacy. [ABSTRACT FROM AUTHOR]

This paper presents an investigation aimed at understanding the shock wave propagation response of oriented α-quartz single crystals by using molecular dynamics (MD) simulations. Several orthorhombic unit cells with different crystal orientations converted from an original monoclinic α-quartz crystal were used to construct the supercells with the crystallographic orientations of [100], [120], and [001] aligned with the shock direction. The shock wave propagation responses were analyzed via position-time (x–t) diagrams of several thermal and mechanical properties. Atomic shear strain and radial distribution function (RDF) were used to investigate the shock-induced material deformation and phase change from crystal to disordered fluid-like flow. The MD simulations enabled the construct of the shock Hugoniot, in terms of the shock velocity Us versus the impact/particle speed Up (i.e., Us–Up plane), and the Hugoniot elastic limit σ HEL response with reference to precursor decay. It was found that the single crystal α-quartz sample exhibits noticeable anisotropic behaviors in terms of kinetic temperature distribution, stress distribution, and Hugoniot shock velocity response. Among the three studied crystal directions at a relatively low Up, the [120] sample showed a non-uniform shock-induced deformation pattern, and the [001] crystal showed the most prominent energy absorption capacity. At a given high impact speed (e.g., Up = 2.5 km/s), the [001] sample showed a relatively longer amorphous shocked region followed by a shorter deformed crystal region, which was very different from the compressed regions behind the shock front in the other two samples. For all oriented crystals, the RDF results predicted an amorphous structure of silica emerging in the compressed region at the higher speed impact, in addition to a few "shear-bands" or crystal sliding in the [120] sample. The shock Hugoniot Us–Up also indicated a noticeable anisotropic behavior of the α-quartz. At a given value of Up above 1.5 km/s, the [001] crystal yielded the largest Us while the [120] crystal yielded the smallest. A "two-wave" structure was evidently found in the [001] sample at Up = 2.5 km/s, while such a structure was not clearly seen for the other two orientations. The precursor decay phenomenon was observed in [001] direction, indicating a strong strain rate effect on σ HEL ; however, the σ HEL decay was not easy to identify in [100] and [120] directions due to the instantaneous microstructural sliding/collapse or fast transition to an extensive amorphous structure behind the shock front. In summary, the MD simulation-based studies reported in the present work demonstrate strong orientation-dependent shock responses of the monoclinic single crystal α-quartz. [ABSTRACT FROM AUTHOR]

The resulting microstructure after the sintering process determines many materials properties of interest. In order to understand the microstructural evolution, simulations are often employed. One such simulation method is the phase-field method, which has garnered much interest in recent decades. However, the method lacks a complete model for sintering, as previous works could show unphysical effects and the inability to reach representative volume elements. Thus the present paper aims to close this gap by employing molecular dynamics and determining rules of motion which can be translated to a phase-field model. The key realization is that vacancy absorption induced motion of grains travels through a grain structure without resistance. Hence the total displacement field of a green body is simply the superposition of all grains reacting in isolation to local vacancy absorption events. The resulting phase-field model is shown to be representative starting from particle counts between 97 and 262 and contains the qualitative correct dependence of sintering rate on particle size. [ABSTRACT FROM AUTHOR]

This paper reports atomistic simulation studies of tensile and compressive behavior of nanowires of a model quinary high entropy face-centered cubic (FCC) alloy. The simulations employ empirical interatomic potentials and use massively parallel molecular dynamics techniques at the atomistic level to study the deformation mechanisms. The studies consider pristine cylindrical nanowires oriented along various crystallographic directions. The focus is the role that local composition fluctuations in the random alloy plays in the deformation response. The deformation behavior observed for the complex random alloy is compared with a corresponding "average atom" material that has the same average properties but no local compositional fluctuations. In all cases, deformation is governed by dislocations emitted from the free surface. Twinning was also found, depending on the crystallographic orientation and loading mode. We show that for all orientations, the high entropy alloy (HEA) wires show the onset of plasticity at lower stress levels than the average atom material. However, after the onset of plasticity, the HEA presents a higher strength, mostly driven by the fact that the dislocations emitted from the surface do not glide as easily in the random alloy as they do in the average atom material. [ABSTRACT FROM AUTHOR]

Molecular dynamics atomistic simulations were used to investigate the tribological properties of NbC/Nb ceramic/metal nano-laminates (CMNLs) during nano-indentation and nano-scratching. The study compared the scratching behavior of the CMNLs to that of NbC and Nb single crystals. Two CMNL models were considered, both featuring a top layer of NbC with differing metallic layer thicknesses of 2 nm and 8 nm. Spherical indenters with radii of 5, 10, and 20 nm were used to scratch the CMNLs with a 3 nm penetration depth, avoiding penetration into the metallic layer beneath the ceramic layer. The results revealed that the alternating metallic and ceramic layers in the CMNL models reduced the amount of material removed during scratching compared to NbC single crystals. The model with the thickest metallic layer showed lower friction coefficient and material removal. The simulations demonstrated that the indenter size had a significant effect on the scratch behavior of CMNLs, with the friction coefficients for the larger indenters being notably lower. The study revealed that larger indenters show less sensitivity to the individual layer thickness in terms of friction coefficients and material removal. The scratching response of the models was linked to the atomic-level deformation mechanisms during the scratching process. The dominant factors affecting the scratching behavior were individual layer thickness, indenter size, and the scratching attack angle. Overall, the study provides valuable insights into the tribological behavior of CMNLs and sheds light on the design of scratch-resistant coatings. [ABSTRACT FROM AUTHOR]

Electrophoretic-deposited (EPD) graphene oxide (GO) on carbon fiber (CF) has been tried to improve the fiber/epoxy interfacial properties. However, the nano-level understanding on the mechanisms of surface wettability is still somewhat limited, which will be important to ensure the manufacturing ability of CF composites. In this work, the interfacial wetting behavior was systematically investigated via molecular dynamics simulations (MD). The results show significant improvement in interfacial properties by changing the morphology of GO-modified fiber surfaces. In details, appropriately increasing the deposition thickness, surface roughness, stacking angle and the distribution uniformity of GO sheets could enhance the wettability of the fiber surface, resulting in higher cohesive strength. The variation of bond stretching energy was the main factor that induced the change of the potential energy of the epoxy system during wetting simulations. Moreover, two obvious peaks of angular bending energy were observed at the solid–liquid and liquid–vapor surface, which may provide further insights into the formation mechanism of interfacial tensions. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are conducted to study the self-diffusion process along a < 100 > Σ5(210) symmetric tilt grain boundary in a model equiatomic FeNiCrCoCu high-entropy alloy (HEA), for the directions both perpendicular and parallel to the tilt axis. For comparison, the grain boundary diffusion process is also quantified for each of the pure components of the HEA. Most importantly, the results are compared with the diffusion along the same grain boundary using the corresponding "average atom" potential that has similar average bulk properties but no compositional randomness as in the HEA. These comparisons show that the self-diffusion in the HEA grain boundary is slower than in the average atom material as well as the average of pure components, suggesting that a "sluggish" diffusion effect exists for this special grain boundary in the HEA. This effect is significant at low temperatures but diminishes at higher temperatures, indicating that the grain boundary sluggish diffusion is likely temperature dependent. Interestingly, the grain boundary sluggish diffusion behavior is different from the bulk diffusion that was studied previously using the same methods and interatomic potentials, in which no significant sluggish diffusion effect was observed. Our further analysis suggests that the combination of the "trapping effect" by compositional complexity in the HEA and the confined 2-D diffusion paths at this special grain boundary is responsible for the observed grain boundary sluggish diffusion. [ABSTRACT FROM AUTHOR]

With density functional theory calculations, we systematically studied the adsorption and migration properties of Li/Na/K ions on the β-In2Se3 monolayer to evaluate the performance of β-In2Se3 as an anode material for alkaline-ion batteries. The dynamical and thermal dynamical stability of the β-In2Se3 monolayer is verified by both phonon and ab initio molecular dynamics simulation. The negative adsorption energies of Li, Na, and K ions on the β-In2Se3 monolayer are −1.93, −1.96, and −2.48 eV, respectively, indicating superior ion affinity for Li/Na/K. The predicted specific capacities are 115 mAh/g (Li) and 230 mAh/g (Na/K), and the related volumetric capacities are 698 mAh/cm3 (Li) and 1396 mAh/cm3 (Na/K), respectively. The corresponding energy densities are estimated at 180, 426 and 413 mWh/g for Li/Na/K. Moreover, the ultra-low diffusion barriers for Li/Na/K ions are predicted to be 0.20, 0.14, and 0.09 eV, suggesting a higher ion mobility on the surface of β-In2Se3 monolayer compared to many previously reported anode materials. The above results suggest that β-In2Se3 can be a promising anode material for (Li/Na/K) ion batteries. [ABSTRACT FROM AUTHOR]

Recently, the HfNbZrTi high-entropy alloy (HEA) has received extensive attention due to its exceptional mechanical properties, which is ascribed to the significant lattice distortion and complex structural evolution induced by inherent chemical short-range order (CSRO). In this study, we employ molecular dynamics (MD) technique to study nanoscale CSRO phenomenon and its influence on the mechanical response of Σ5(210) and Σ5(310) grain boundaries (GBs) in HEA under shear loadings. Results reveal an apparent CSRO manifested by clustering of Hf-Nb and Zr-Ti pairs consistent with experimental observations. Further analyses on some representative Σ5 GB models unveil that the presence of CSRO can induce transformation of GB structure, which not only causes a transition in deformation behavior from migration-dominated to sliding but also raises the yield strengths. Moreover, after probing into the stress–strain curves and the relative sliding energy curves of massive GB models, we discover that the transition in GB behavior is ascribed to the CSRO impeded dislocation motion. The findings of this work promote atomistic understanding on the CSRO modulated shear response of GBs in HfNbZrTi HEA. [ABSTRACT FROM AUTHOR]

To improve the thermal stability of the explosive HMX (C4H8N8O8), in this study, different functional groups (hydroxyl, carboxyl and butyl) were grafted on the surface of graphene, and the corresponding thermal transport across graphene–HMX interface is studied by molecular dynamics simulations. The obtained results show that the covalent functionalization coverage rate of less than 7.5% is not beneficial for the interface heat transfer; however, further increasing the coverage rate significantly boosts the interfacial thermal conductance (ITC). Among the studied functional groups, butyl best enhances the ITC compared to hydroxyl and carboxyl groups, with an increase of 48.5% compared to that of the pristine graphene–HMX. Then, the obtained results from molecular dynamics simulations serve as input for the effective medium theory-based thermal conductivity prediction model, and the effective thermal conductivity of graphene–HMX composites were investigated. Meanwhile, the major factors that dominate the composite thermal conductivity were identified. Our investigation enriches the understanding of the physical mechanisms governing the heat transport in HMX composites with fillers and is instructive for the structural design of thermally conductive HMX-based explosives. [ABSTRACT FROM AUTHOR]

3-Nitro-1,2,4-triazole-5-one (NTO) is a potential alternative to TNT, RDX and HMX in high energy density materials (HEDMs) due to its inexpensive synthesis, excellent detonation performance, low impact sensitivity, and high thermal stability, but its underlying thermal decomposition mechanism is ambiguous. In this work, we carry out molecular dynamics simulations based on self-consistent charge density functional tight binding method to study the thermal decomposition mechanism of condensed phase NTO and consider surface and molecular vacancy effects. We observe that the initial decomposition reaction is mainly the rupture of intramolecular chemical bonds, and three primary reaction channels are proposed: cleavage of nitro group (C5 − N5 bond fracture), rupture of C3 − N2 bond in the ring and H atom transfer to carbonyl, in which C5 − N5 bond breaking plays a leading role under high temperature. At molecular vacancy and on surface, we find that the activation barriers of nitro group cleavage and H atoms migration are lower than that in ideal bulk NTO, indicating effective regulations of them on the thermal stability and decomposition reaction kinetics of NTO crystal. The above proposed reaction mechanism and the effects of molecular vacancy and surface are verified from electronic structure calculations and TG-DSC experiment with coarse and fine NTO samples. Our work may shed some light on designing HEDMs with better performance, safety and usability. [ABSTRACT FROM AUTHOR]

In this study, the extreme tension wave front profile (pull speed up to 1.6 km/s) in pure aluminum (density 2.7 g / cm 3 ) is analyzed using the LAMMPS molecular dynamics (MD) code and based on the tension conservation equations of mass, momentum, and energy. The simulation results agree favorably with the theoretical calculation. The profile of the extreme tension wave front is observed from the MD code simulation, and a typical shockless ramp wave front formation is identified during forced extreme tension loading. Further analysis was accomplished based on the formation of the ramp wave front, illustrating the behavior of the isentrope of aluminum under extreme tension loading. [ABSTRACT FROM AUTHOR]

Non-equilibrium molecular dynamics was used to simulate the diffusion behavior and reaction mechanism of elements at the solid–liquid interface of Zn–2.0Al–1.5Mg coating on Fe matrix at 1300 K. The simulation results showed that the solid–liquid interface was controlled first by diffusion and then by reaction. Analyzing the atomic distribution and atomic number density, it was found that the diffusion depth and diffusion rate were Zn > Mg > Fe > Al, which was consistent with the experimental results. The Al atoms aggregated to form the Fe–Al intermetallic compounds layer, and the Mg atoms aggregated in the Fe–Al intermetallic compounds layer in the form of segregation. Then a short-time simulation at 800 K and 50 ps was carried out, and the results showed that the surface of the Fe matrix would melt, and the Fe atoms first entered the liquid phase, and then, the liquid atoms diffused into the solid phase in the form of occupying vacancies. Through the analysis of common neighbor atoms, it was found that the interdiffusion of Zn and Fe atoms produced Fe–Zn intermetallic compounds Fe3Zn10, which had a typical BCC crystal structure; and the formation of Fe–Al intermetallic compounds layer hindered the further diffusion of Zn atoms. The study results provide a theoretical basis for the diffusion and reaction mechanism of the solid–liquid interface in the initial stage of hot-dip plating. [ABSTRACT FROM AUTHOR]

High-temperature proton exchange membranes (HTPEMs) based on arginine-modified phosphoric acid-doped polybenzimidazole (Arginine-PBI-PA) and poly(tetrafluoroethylene) phosphoric acid-doped polybenzimidazole (PTFE-Arginine-PBI-PA) were fabricated and characterized for fuel cell applications. Arginine as filler was used to prepare HTPEMs for the first time, and the Arginine-PBI-PA membrane exhibited an excellent proton conducting ability with 24.1 mS cm−1 at 160 °C while maintaining mechanical strength. Furthermore, Arginine-PBI-PA composite membrane was also appropriate for membrane electrode assemblies (MEAs), and it exhibited better fuel cell performances (0.68 V@400 mA cm−2) compared with the PBI-PA membranes prepared. Molecular dynamics (MD) simulation revealed that the better electrochemical properties of Arginine-PBI-PA membranes over PBI-PA membranes were ascribed to the strong interactions between the basic sites and carboxyl groups of arginine and PA molecules, respectively. In addition, the higher proton conductivity for Arginine-PBI-PA membranes was attributed to the formation of a tighter H-bonding network and the interaction between arginine non-protonated oxygen (O) and PA protons (HPA). Experimental investigation and molecular dynamics simulation of novel arginine/PBI composite membranes for high temperature PEM fuel cells [ABSTRACT FROM AUTHOR]

In this work, coating of various metals on carbon nanotubes was carried out by magnetron sputtering and molecular dynamics simulation. Transmission electron microscopy and simulation studies reveal that three modes of metal nucleation on the carbon nanotube surface: particle growth, island growth and film growth. The nucleation mode was mainly affected by three factors: the initial energy of the metal before reaching the carbon nanotube surface, the energy required for carbon nanotube to bond with metal, and the diffusion energy of metal atoms on the carbon nanotube surface. Based on the analysis of the jump trajectory, potential energy and temperature change of metal atoms in molecular dynamics simulation, the method of improving deposition ratios by alloying and increasing deposition rate was proposed and verified by simulation and experiments. These results provided us a new way to regulate the interface structure and nucleation model of carbon nanotubes and metals. [ABSTRACT FROM AUTHOR]

Additive-free nano-polycrystalline diamond (nPCD) composite was sintered by using a mixture of micro-diamond (MD) and onion-like carbon (OLC) as raw materials at 4–6 GPa/1000–1400 °C/5–30-min holding time. The composition, morphology, microstructure, density, and hardness of the nPCD composite were measured by XRD, FESEM, HRTEM, Archimedes principle, and Vickers hardness tester. Molecular dynamics of OLC with MD addition phase transition to nPCD at HPHT was calculated. The effect of MD and high-pressure sintering parameters on the OLC transformation process and the composition, microstructure, properties of nPCD composite were studied. The results showed that the MD was uniformly distributed in the nPCD composite. MD acted as the nucleus to promote the conversion of OLC to diamond. The increase in sintering pressure enhanced the density and hardness of the nPCD composite. When the sintering pressure was raised from 4 to 6 GPa, the density of the nPCD composite was increased from 2.72 to 3.02 g/cm3, and the hardness was increased from 41.85 to 56 GPa. The increase in sintering temperature and holding time made the density and hardness of the nPCD composite increase first and then decrease. Nanotwinned diamond with 10-nm size appeared in the nPCD region in the nPCD composite. The presence of nanotwinned diamonds increased the hardness of the nPCD composite. [ABSTRACT FROM AUTHOR]

In this contribution, molecular dynamics method is used to accurately add quantitative Co atoms in the grain boundary (GB) region of nano-polycrystalline Ni to study the effect of solute atoms on the GB and the deformation mechanism of the material. It was found that adding an appropriate amount of Co atoms at the GBs can improve the tensile strength of the material to a certain extent through solid solution strengthening. However, excessive introduction of solute atom will increase the activity of GB atoms, destroy the stability of GBs, and accelerate the appearance of material yielding. At the same time, the Co atoms at the GB gradually detached from the GB region and diffused into the grains. In addition, the dislocations are distributed in a grid at the GBs, and with the increase in strain, the number and length of dislocations gradually increase, forming a large number of entanglements. Moreover, the Shockley dislocation interacts with other dislocations to form a more stable dislocation structure by hindering the generation and movement of other dislocations, which greatly enhances the strength of the system. [ABSTRACT FROM AUTHOR]

Here we contrast the molecular dynamics of epoxy nanocomposites filled with three different types of silica-based nanoparticles with different architectures, namely solid core, core–shell and hollow and with varying degree of crystallinity. The samples are characterised by Fourier transform infrared spectroscopy, differential scanning calorimetry, broadband dielectric spectroscopy and dynamic mechanical analysis (DMA). Widely known relaxations such as α, β, γ, normal mode and interfacial polarisation are observed and discussed. An additional relaxation named omega (ω) is also observed, whose dielectric strength is inversely correlated to the crystallinity of the nanoparticles. We suggest that this may be attributed to the polarizing interaction of the hydroxyl groups of silanols with the hydroxy ether groups of the polymer chain. The ω is absent in DMA confirming it as a polarisation phenomenon. At lower concentration of silanols, the ω largely overlaps with β, effectively becoming an integral part of it. Finally, two interfacial polarisation relaxations are observed in the case of core–shell structures, originating from the core–shell and shell–polymer interface but, due to the similar real permittivity values of the core, shell and the polymer, their dielectric strength is weak. [ABSTRACT FROM AUTHOR]

The Hall–Petch relationship and deformation process in Ti3Al nano-polycrystalline alloys are investigated using molecular dynamics simulations in this research. The impact of different grain sizes and temperatures on mechanical characteristics was considered. Different Hall–Petch relations were detected for samples with the grain sizes ranging from 2 to 20 nm, inverse Hall–Petch relations in big grain sizes ranges, and positive Hall–Petch relations in the medium grain size region, respectively. A transition zone formed at the interception of positive and inverse Hall–Petch relations, which will vanish as the temperature rises. The critical grain size of the positive Hall–Petch relation decreases as the temperature rises from 10 to 600 K. With the grain size increases in the smaller grain size range, the yield stress increases, which is made by the grain boundary motion and rotation. Besides, temperatures affect mechanical characteristics. The rising temperatures lead to the decreasing dislocation density and a high grain boundary fraction. [ABSTRACT FROM AUTHOR]

The influence of ionic liquids (ILs) on the friction of diamond-like carbon (DLC) films is investigated via molecular dynamics simulation. The effects of load, amount of ILs molecules, roughness and sliding velocity are considered. It is found that a large amount of ILs films can prevent the formation of C–C bonds between sliding interfaces. The friction in this case increases with loads, due to a closer arrangement of ILs and high cohesive energy between ILs and DLC films. Moreover, for the cases with a small amount of ILs under a large load, the ILs molecules are locally distributed, inducing the transition of the lubrication state from fluid lubrication into boundary lubrication, which promotes the interfacial C–C bonds formation and accounts for large friction. Furthermore, the integrity of ILs films is broken by high sliding velocity, but the friction is almost unchanged. This is because the graphitization level of DLC films increased by the high velocity can eliminate the friction enhancement by the bond formation between these films. Fast Fourier transform (FFT) analyses show that the frequency of friction oscillations generally agrees well with that of the velocity of center of mass, demonstrating that the intrinsic diffusion properties of ILs determine the friction mechanisms. [ABSTRACT FROM AUTHOR]

The martensitic transformation in pure Fe and its alloys has been studied over many decades. Several theoretical models have been proposed to describe the atomic motion that leads to the fcc-to-bcc martensitic transformation. However, such models do not account for the effect of pre-existing planar defects such as twin boundaries and stacking faults, present in the high-temperature austenite phase prior to the transformation process. This work systematically studies the role of nano-spaced planar faults with different inter-spacing on the martensitic transformation using molecular dynamics simulations. Research shows that the investigated planar defects affect the nucleation and growth mechanisms during martensite formation, the morphology of the resulting microstructure, the specific atomic path leading to the phase transformation, and the martensite start temperatures. Martensite variants were identified by the analysis of the atomic shears and slip systems during the transformation process. A crystallographic analysis is done to explain the existence of different shear mechanisms of martensite transformation at different locations in the fcc austenite. The present investigation provides fundamental insights into the martensitic transformation process in presence of pre-existing planar defects and can be applied to other material systems, e.g., Fe alloys. [ABSTRACT FROM AUTHOR]

Imidazole-substituted thiazolyl[5,4-d]thiazole (TTz) based on two [3.3.0] thiazole-fused rings was synthesized with the advantages of one-step synthesis, easy separation and purification. The inhibition effect and the mechanism on the corrosion behavior of mild steel in 1 M HCl solution was investigated by means of weight loss tests, electrochemical measurements, morphology analysis and theoretical calculation methods. The maximum corrosion inhibition efficiencies of 2-ImTTz and 4-ImTTz are 95.79% and 90.03%, respectively. The measurement of EIS indicated that the corrosion inhibition process is controlled by charge transfer. Quantum chemical calculations revealed the relationship between corrosion inhibition and global reactivity descriptors. Molecular dynamics simulation showed the parallel adsorption of the corrosion inhibitor on the Fe(110) surface in both neutral and protonated forms. The corrosion inhibition mechanism was proposed and discussed. [ABSTRACT FROM AUTHOR]

Nanostructured tantalum (Ta)-based dental implants have recently attracted significant attention thanks to their superior biocompatibility and bioactivity as compared to their titanium-based counterparts. While the biological and chemical aspects of Ta implants have been widely studied, their mechanical features have been investigated more rarely. Additionally, the mechanical behavior of these implants and, more importantly, their plastic deformation mechanisms are still not fully understood. Accordingly, in the current research, molecular dynamics simulation as a powerful tool for probing the atomic-scale phenomena is utilized to explore the microstructural evolution of pure polycrystalline Ta samples under tensile loading conditions. Various samples with an average grain size of 2–10 nm are systematically examined using various crystal structure analysis tools to determine the underlying deformation mechanisms. The results reveal that for the samples with an average grain size larger than 8 nm, twinning and dislocation slip are the main sources of any plasticity induced within the sample. For finer-grained samples, the activity of grain boundaries—including grain elongation, rotation, migration, and sliding—are the most important mechanisms governing the plastic deformation. Finally, the temperature-dependent Hall–Petch breakdown is thoroughly examined for the nanocrystalline samples via identification of the grain boundary dynamics. [ABSTRACT FROM AUTHOR]

The corrosion inhibition behaviors of dodecylpyridinium chloride (DPC), hexadecylpyridinium chloride monohydrate (HDPC), and the rosin amino acid surfactants dehydroabietic acylamino sodium (6-DAS) and compounds (6-DAS/DPC and 6-DAS/HDPC) were investigated by weight loss measurements and electrochemical testing. Besides, corrosion inhibition performance was further verified by combining a series of surface properties analyses and theoretical calculations. The weight loss results showed that the increase in inhibition efficiency was mainly attributed to its high concentration and revealed that the inhibition efficiency of compound inhibitors was higher than that of single inhibitor 6-DAS (92.23%), which was up to 95.86% and 96.72% of 6-DAS/DPC and 6-DAS/HDPC at 1:8 concentration ratio, respectively. The potential polarization curve potential demonstrated that single inhibitor 6-DAS and compound inhibitors (6-DAS/DPC and 6-DAS/HDPC) were both mixed-type corrosion inhibitors dominated by the anode. Thus, among the three, 6-DAS/HDPC had the best corrosion inhibition performance, and the average inhibition efficiency was 96.90%. Surface studies presented the adsorption of inhibitor molecules adhered on the Fe surface, while the adsorption performance of compound inhibitors appeared to be superior to single inhibitor 6-DAS. Moreover, it was found that there were a few excellent data from molecular dynamics simulation about the adsorption energies of inhibitors that could also explain the corrosion inhibitor performance, the results of which had good agreement with the experimental data, which provided strong evidence for the close relationship between the molecular structure of inhibitor and its inhibition efficiency. [ABSTRACT FROM AUTHOR]

The fretting wear behaviors and mechanism of a high Nb–TiAl alloy with full lamellar microstructure at ambient temperature were investigated. The fretting wear mechanism of the alloy under different loads and displacement amplitudes was revealed using experiments and molecular dynamics simulations. The results showed that the load and displacement amplitude significantly affected fretting wear behaviors and the mechanism of the Ti–45Al–9Nb alloy. Higher load and lower displacement amplitude could effectively reduce the fretting wear of the alloy. Molecular dynamics simulation results showed that the order-twin lamellar interface hindered the deformation and dislocation movement of twins, improved the mechanical properties of the material, and improved the wear resistance of such alloy. The wear mechanism of Ti–45Al–9Nb alloy was adhesive wear and surface fatigue wear. [ABSTRACT FROM AUTHOR]

Employing isothermal molecular dynamics, we simulated the self-assembly of core-shell nanostructures in the course of quenching binary Ni–Al nanoparticles (NPs) with initially homogeneous distributions of both components. The process of quenching was reproduced via the uniform rapid cooling of initial configurations from temperatures of 1000 K down to 0.001 K. To increase the reliability of the simulation results, we used two independently developed computer programs (our own and the well-known open program LAMMPS) in conjunction with the tight-binding potential (TBP) model and the embedded atom method (EAM). Simulations employing both force fields predict the self-assembly of the core-shell nanostructures whose shells consist of Al atoms. However, involving TBP predicts the formation of more perfect Ni@Al structures, in which the central area (core) consists almost completely of Ni atoms, whereas EAM simulations predict formation of a more complex integral structure Ni–Al@Ni@Al. In the last case, the first (outer) monolayer also entirely consists of Al atoms, the second—of Ni atoms, while the core is comprised of both types of atoms. At the same time, the core is enriched by Ni atoms. It is concluded that the spontaneous surface segregations of Al atoms should be considered as the main driving force for the formation of the core-shell structures during quenching of Ni–Al NPs with initially homogeneous distributions of components. [ABSTRACT FROM AUTHOR]

The deformation behavior of neutron-irradiated metallic glasses (MGs) has been conducted by strategically hybridizing synchrotron radiation experiments with molecular dynamics simulations. A unique and phenomenal mechanism of rejuvenation in MGs has been found in contrast to the inherent degradation in plasticity that undermines the performance of crystalline nuclear alloys. By neutron irradiation, the induced atomic structural disordering evoked an increase in free volumes with an associated reduction in densely packed Voronoi clusters, forcing the precipitation of some local regions with high irradiation-induced potential. Upon stress activation, these local regions were energized by an atomic flux to trigger a multifold of shear transition zones (STZs). The propagation of STZs along more than one orientations to form the cross blocking of shear bands and consequently evolved a novel plasticity-enhanced rejuvenation effect. The implication of this study is far-reaching upon the discovery of a definitive correlation between irradiation-induced structural mechanisms and the unique structural responses of MGs, which can feasibly be extended to other amorphous systems in advancing the design and application of novel nuclear structural materials. [ABSTRACT FROM AUTHOR]

J Mater Sci, 1-15 13 Coutinho YA, Kunwar A and Moelans N (2022) Phase-field approach to simulate BCC-B2 phase separation in the AlnCrFe2Ni2 medium-entropy alloy. J Mater Sci, 1-13 14 Siddique AB and Khraishi TA (2022) Multi-scale modeling of solute atom strengthening using 3D discrete dislocation dynamics. [Extracted from the article]

Understanding the deformation behavior of metallic materials at high strain rates requires the characterization of plasticity contributors, such as twins, phase transformed regions, and dislocations. However, predicting the contributions from phase transformation and twinning relies on a complete understanding of the selection of variants for various loading orientations and the evolution of their volume fractions. This manuscript presents a new virtual texture (VirTex) analysis approach to characterize phase transformation and twinning variants in deformed microstructures generated using molecular dynamics (MD) simulations. The VirTex method involves the construction of a rotation matrix to calculate the angle/axis pairs and misorientation angles for each atom in the microstructure. Any changes in the orientation angle from angle/axis pairs and/or structure types are analyzed to determine the nucleation and evolution of variants in the microstructure. The study uses shock deformed single-crystal Fe, Ta, and Cu to analyze the variant selections for phase transformation or twinning or both in BCC and FCC systems. In addition, the VirTex analysis is able to characterize the phase transformation and twinning variants in nanocrystalline Fe and Ta microstructures. Besides characterizing variants, orientation mapping also provides an accelerated and on-the-fly approach for quantifying twin fractions in MD microstructures. [ABSTRACT FROM AUTHOR]

Computational tools to study thermodynamic properties of magnetic materials have, until recently, been limited to phenomenological modeling or to small domain sizes limiting our mechanistic understanding of thermal transport in ferromagnets. Herein, we study the interplay of phonon and magnetic spin contributions to the thermal conductivity in α -iron utilizing non-equilibrium molecular dynamics simulations. It was observed that the magnetic spin contribution to the total thermal conductivity exceeds lattice transport for temperatures up to two-thirds of the Curie temperature after which only strongly coupled magnon-phonon modes become active heat carriers. Characterizations of the phonon and magnon spectra give a detailed insight into the coupling between these heat carriers, and the temperature sensitivity of these coupled systems. Comparisons to both experiments and ab initio data support our inferred electronic thermal conductivity, supporting the coupled molecular dynamics/spin dynamics framework as a viable method to extend the predictive capability for magnetic material properties. [ABSTRACT FROM AUTHOR]

Mass transport along grain boundaries in alloys depends not only on the atomic structure of the boundary, but also its chemical make-up. In this work, we use molecular dynamics to examine the effect of Cr alloying on interstitial and vacancy-mediated transport at a variety of grain boundaries in Ni. We find that, in general, Cr tends to reduce the rate of mass transport, an effect which is greatest for interstitials at pure tilt boundaries. However, there are special scenarios in which it can greatly enhance atomic mobility. Cr tends to migrate faster than Ni, though again this depends on the structure of the grain boundary. Further, grain boundary mobility, which is sometimes pronounced for pure Ni grain boundaries, is eliminated on the time scales of our simulations when Cr is present. We conclude that the enhanced transport and grain boundary mobility often seen in this system in experimental studies is the result of non-equilibrium effects and is not intrinsic to the alloyed grain boundary. These results provide new insight into the role of grain boundary alloying on transport that can help in the interpretation of experimental results and the development of predictive models of materials evolution. [ABSTRACT FROM AUTHOR]

We examine the mechanism of pyrolysis and charring of large (> 10,000 atom) phenol–formaldehyde resin structures produced using pseudo-reaction curing techniques with formaldehyde/phenol ratios of 1.0, 1.5 and 2.0. We utilise Reactive Molecular Dynamics (RMD) with a hydrocarbon oxidation parameter set to simulate the high-temperature thermal decomposition of these resins at 1500, 2500 and 3500 K. Our results demonstrate that the periodic removal of volatile pyrolysis gasses from the simulation box allows us to achieve near complete carbonisation after only 2 ns of simulation time. The RMD simulations show that ring openings play a significantly larger role in thermal decomposition than has previously been reported. We also identify the major phases of phenolic pyrolysis and elucidate some of the possible mechanisms of fragment formation and graphitisation from the RMD trajectories and compute the thermal and mechanical properties of the final pyrolysed structures. [ABSTRACT FROM AUTHOR]

A new high-precision angular-dependent potential of the Ni–Pd system was obtained by fitting the experimental data and first-principles calculations. Then, the element segregation characteristics and thermal stability of Ni–Pd bimetallic nanoparticles were investigated by Monte Carlo method and molecular dynamics method. The results show that the chemical ordering pattern of PdxNi1 − x nanoparticle is the result of the competition of surface energy, strain energy, bond energy and interface energy. When a small amount of Pd atoms are substitutionally doped into the Ni nanoparticle, all the Pd atoms will be segregated on the surface and dispersed. The synergistic effect of Ni atoms and Pd atoms in the surface will improve the catalytic activity and carbon deposition resistance of PdxNi1 − x nanoparticle catalyst in methane dry reforming reaction. Increasing the doping amount of Pd atoms will gradually reduce the melting point of PdxNi1 − x nanoparticle, thereby reducing its sintering resistance. [ABSTRACT FROM AUTHOR]

The interaction mechanisms between dislocations and coherent twin boundary (CTB) were determined with molecular dynamics simulations. The dislocation slip rate is found to depend on the temperature and the shear rate. The edge and screw dislocations displayed different mechanisms when they interacted with the CTB. The edge dislocation could pass through the CTB, leaving a twinning dislocation to heal the boundary, while the screw dislocation was absorbed by the CTB. The activation energy of overcoming the CTB was also calculated. The energy barrier for the edge dislocation to pass through the CTB was much higher than that needed for the screw one to be absorbed. [ABSTRACT FROM AUTHOR]

The electrically conductive and optically transparent flexible nanocomposites made of polymers and multi-walled carbon nanotube (MWCNT) have the potential to be used as a transparent substrate for optoelectronic applications. In this investigation, we have fabricated a series of nanocomposites of MWCNT, used as conductive filler, with a copolymer of methyl methacrylate and acrylonitrile as a matrix, and solution blending method was used to achieve suitable dispersions. The MWCNT content varied sequentially in these nanocomposite thin films. A detailed study about the dispersion of MWCNTs in the matrix was done by attenuated total reflectance-infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The surface roughness is continuously increasing with an increase in the amount of conductive filler in the polymer matrix. However, it never exceeds 10 nm, which is very small compared to the MWCNT length, and also confirmed nearly complete embedding of conducting filler in the insulating matrix. The diffusion coefficient of nanocomposite was investigated for O2 and H2O with Molecular Dynamics simulations and found to decrease with increasing load percentage of MWCNT. The thin film's optical transmittance and electrical conductivity are characterized thoroughly. An optimized formulation of nanocomposite with 0.25% MWCNT has shown enhanced conductivity of 10–2 S/cm (semiconductive range) with ~ 94% optical transparency at 550 nm. [ABSTRACT FROM AUTHOR]

The bonding performance between epoxy resin and cement-based materials affects the load transfer capacity between fiber-reinforced polymers (FRP) and concrete. FRP-reinforced concrete structures are inevitably exposed to aggressive environments during service, triggering interfacial deterioration and premature structural failure. To assess the stress state of FRP-reinforced concrete structures and to predict their long-term durability, a fundamental investigation of the bonding performance of the epoxy/concrete interface in aggressive environments is required. In this study, the bonding performance between epoxy resin and calcium silicate hydrate (CSH) in water and salt environments is investigated using molecular dynamics (MD) simulations. The adhesion energy of epoxy/CSH interface calculated via combine MD simulation and Bell's model theory is dramatically reduced in water and salt environments. Analysis of the static structures and dynamic properties reveals that the adhesion between the epoxy resin and CSH matrix is mainly dependent on the O–Ca–O and H-bond connections, while the water and salt environments significantly weaken these connections and disrupt the integrity of the epoxy/CSH interface. This study provides a molecular-level understanding of the bonding degradation at the epoxy/CSH interface in aggressive environments. This study provides a molecular level understanding of the bonding degradation between epoxy and CSH matrix in aggressive environments. [ABSTRACT FROM AUTHOR]