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In our present study, under uniaxial tension, atomistic simulations were conducted to explore the crack propagation mechanism of Square Nickel Plate (SNP) for two distinct shaped cracks (Rectangular and Circular) at center separately. Here, for modeling the inter-atomic potential between atoms, Embedded Atom Model (EAM) was used. In case of both types, the crack size was varied keeping a constant strain rate of 2×109s-1and temperature of 300 k for investigation of the effects of crack geometry and size on the behavior of crack propagation. Along with the size and geometry of crack, the effects of different strain rates (1×109, 2×109and 4×109s-1) and temperatures (300 K, 600 K and 900 k) were also studied. From the simulations, the declination nature of peak stress can be deduced for both of the geometries by increasing the crack size. It can also be concluded that when crack area was same, the peak stresses were higher in SNP with Circular crack than with the SNP with Rectangular one. Besides, increasing and decreasing nature of peak stress were found for two genres with the increment of strain rate and temperature separately.

A combined experimental and simulation study is carried out to compare the properties of amorphous Ni100-x P x alloys obtained by electroless deposition and rapid melt-quenching. The onset of crystallization of experimental electroless deposited amorphous films is measured by differential scanning calorimetry experiments. Classical molecular dynamics simulations using Embedded Atom Model-based interactions are performed to obtain glassy Ni-P by melt-quenching the liquid with various quenching rates, as well as via low-energy chemical deposition to mimic experimental electroless deposition. It is shown that the deposited amorphous and glassy states display similar short-range order. The amorphous deposit corresponds to a glassy state obtained with a cooling rate of 109 K s-1, indicating that deposition yields generally more relaxed amorphous structures. The appearance of phosphorus-enriched surface on the simulated deposited thin film, comparable to experimental observations, is discussed.

Variety of interatomic potentials for magnesium can be found in the literature. Result of computer simulations can be slightly different depending on used potential. Particularly, twin boundary structure with the lowest energy can be different in a frame of different models. Comparison of several popular embedded-atom method potentials is provided. It is shown that either reflection or glide structure of twin boundary has the lowest energy for different potentials.

In previous work, bond-order potentials (BOPs) have been used to establish a general yield criterion, different from the Schmid law, for the glide of 〈1 1 1〉/2 screw dislocations on {1 1 0} planes in body-centered cubic metals, while their applications are restricted to the 2D simulations at 0 K because of their low computational efficiency. On the other hand, embedded-atom-method (EAM) potentials have been generally employed for long dislocation segments at finite temperatures, but there is no study to clarify whether or not they can reproduce the yield criteria revealed by the BOPs. In this work, systematic atomistic simulations with an EAM potential have been performed to calculate the behaviors of 〈1 1 1〉/2 screw dislocations in α-iron under different loading conditions. We find that at 0 K, the simulation results can be well explained by the general yield criterion when the glide is restricted to {1 1 0} planes. Under uniaxial loadings, the activated slip systems are consistent with the experimental observations. At finite temperatures, as a preliminary attempt, the influence of the non-glide stress on the slip planes is presented, which could not be rationalized by the yield criterion at 0 K because extra effect from temperatures has come into the picture.

The wetting characteristics of lithium droplet on different iron surfaces are investigated in details by using molecular dynamics simulations associated with the modified analytic embedded atom model potential. In addition to the wettability of Li droplet on Fe (1 0 0), (1 1 0) and (1 1 2) surfaces, the wetting behavior on a polycrystalline Fe surface is studied. The results show that liquid Li can perfectly wets Fe surfaces, and the wetting behavior of Li droplet is isotropic on Fe (1 0 0) and (1 1 0) surfaces, but anisotropic on Fe (1 1 2) and polycrystalline Fe surfaces. For the Fe (1 1 2) surface, the anisotropic wetting is attributed to the lower energy barriers of Li atom diffusion along the [ 1 1 1 ¯ ] orientation on the Fe (1 1 2) surface. We have proposed a new method for describing the wetting behavior of liquid on substrates in atomic scale by measuring the time-dependent ‘contact atom number’. The unified description of the liquid wetting on both single crystal and polycrystalline surfaces is achieved by this method. Li droplet wetting on the Fe (1 1 0) has the fastest spreading rate, and the spreading rate on the polycrystalline Fe surface is only faster than that on the Fe (1 0 0) surface. In addition, the effect of temperature on the wettability is examined, and it is found that the faster spreading occurred with increasing temperature.

Solidification of the Sm-rich Al–Sm alloys has been studied using a newly developed Al–Sm embedded atom model potential by molecular dynamics (MD) simulations. We use descriptors for glass forming ability that have been previously validated for Al-rich Al–Sm alloys, and we predict that among the Sm-rich alloys the best glass formers have compositions between 65 and 75 at.% of Sm. To test this prediction, Al35Sm65 and Al25Sm75 alloys were synthesized by melt spinning. These alloys have been found to be good glass formers, in agreement with predictions from MD simulations. We also synthesized Al10Sm90, which according to MD results should have a low glass forming ability. Indeed, after the melt spinning, the Al10Sm90 was found to be crystalline as verified by multiple experimental characterization techniques. This is the first time that Sm-rich Al–Sm metallic glasses with enhanced glass forming ability have been experimentally synthesized. Our results also demonstrate the capability of specific structural descriptors to predict glass forming ability of Al-based alloys.

We use the coexisting phases approach to calculate melting phase diagrams of several Fe-C interaction potentials, such as Embedded Atom Method (EAM) potential of Lau et al. [Phys. Rev. Lett. 98 (2007) 215501], EAM potential of Hepburn and Ackland [Phys. Rev. B 78 (2008) 165115], and two flavours of the Analytic Bond Order potential (ABOP) of Henriksson and Nordlund [Phys. Rev. B 79 (2009) 144107]. Melting of both bcc (ferrite) and fcc (austenite) crystals is investigated with C concentrations up to 5 wt%. The results are compared with the experimental data and suggest that the potential of Hepburn and Ackland is the most accurate in reproducing the melting phase diagram of the ferrite, although the austenite cannot be stabilized at any C concentration for this potential. The potential of Lau et al. yields the best qualitative agreement with the real phase diagram in that the ferrite-liquid coexistence at low C concentrations is replaced by the austenite-liquid coexistence at higher C concentrations. However, the crossover C concentration is much larger and the ferrite melting temperature is much higher than in the real Fe-C alloy. The ABOP of Henriksson and Nordlund without the Ziegler-Biersack-Littmark (ZBL) correction correctly predicts the relative stability of ferrite and austenite at melting, but significantly underestimates the solubility of C in the solid phases, while the same potential with the ZBL correction predicts the austenite to be more stable compared to the ferrite at all C concentrations near the melting transition.

It is generally accepted that the complicated character of the interparticle interaction in liquid metals is reproduced most correctly by many-particle potentials of the EAM-type (embedded atom model) interparticle interaction. It is shown that in the case of liquid lithium near the melting temperature (Tm = 453.65 K), the spherical pseudopotential provides a better agreement with experimental data on elastic and inelastic X-ray scattering as compared to the known EAM potentials. The calculations of the dynamic structural factor and spectral densities of the longitudinal and transverse atomic currents lead to the conclusion that although the pseudopotential and EAM potentials generate a certain qualitative correspondence in the features of collective dynamics, the interparticle interaction of the spherical type reproduces correctly the general form of the dynamic structure factor in a certain wavenumber range, as well as the dispersion relation for collective excitations.

In this study, molecular dynamics simulations based on the embedded atom model (EAM) potentials were carried out to investigate influences of cooling rate on the ordered atomic structure, especially icosahedral short- and medium-range orders (ISRO and IMRO) in the Cu64Zr36 metallic glass (MG). It is found that potential energy of the system is strongly dependent on the cooling rate during the rapid solidification, and so does the glass transition temperature (Tg) which rises with increasing cooling rate. Both Honeycutt-Anderson bond pair and Voronoi polyhedra analyses indicate that icosahedral clusters are prominent in the Cu64Zr36 MG and the population of icosahedral polyhedra increases with decreasing cooling rate. The size of IMROs constructed by ISROs via the linkage of vertex-, edge-, face-, and intercrossed-shared atoms becomes larger as the cooling rate and temperature descend. The structural evolution with temperature manifests that the development of icosahedral ordering is the structural origin of the glass transition of the modeled alloy. Moreover, we found that the major structural units in the Cu64Zr36 MG are Cu8Zr5 and Zr6Cu10 polyhedra for Cu- and Zr-centered clusters, respectively, which are different from the main competing crystalline phase upon cooling. The good glass-forming ability of the modeled alloy is originated from the chemical and structural discrepancy between these main clusters and the competing phase, which effectively retards the crystal nucleation in the Cu64Zr36 alloy during rapid solidification.

Molecular dynamics with the modified embedded atom model (MEAM) for interatomic interaction is applied to direct simulations of dislocation dynamics in fcc δ-phase Pu-Ga alloys. First, parameters of the MEAM potential are fitted to accurately reproduce experimental phonon dispersion curves and phonon density of states at ambient conditions. Then the stress-velocity dependence for edge dislocations as well as Pierls stress are obtained in direct MD modeling of dislocation motion using the shear stress relaxation technique. The simulations are performed for different gallium concentrations and the dependence of static yield stress on Ga concentration derived demonstrates good agreement with experimental data. Finally, the influence of radiation defects (primary radiation defects, nano-pores, and radiogenic helium bubbles) on dislocation dynamics is investigated. It is demonstrated that uniformly distributed vacancies and nano-pores have little effect on dislocation dynamics in comparison with that of helium bubbles. The results of the MD simulations evidence that the accumulation of the radiogenic helium in the form of nanometer-sized bubbles is the main factor affecting strength properties during long-term storage. The calculated dependence of static yield stress on helium bubbles concentration for fcc Pu 1 w t . % Ga is in good agreement with that obtained in experiments on accelerated aging. The developed technique of static yield stress evaluation is applicable to δ-phase Pu-Ga alloys with arbitrary Ga concentrations.

In this computational work, the mechanical behavior of silicon (Si) samples in the presence of iron (Fe) nanoparticles is investigated by using the Molecular Dynamics (MD) method. Technically, in our simulations, Si sample and Fe nanoparticles are represented by Embedded Atom Model (EAM) for atomic interaction parameter. The MD simulation results on atomic structure’s mechanical behavior have been reported by calculating some physical parameters such as potential energy (per atom), temperature, Young’s modulus, and ultimate strength. The results indicate the atomic stability of the Si-Fe structure just after 5 ns. By inserting the Fe nanoparticles into the pristine Si sample, Young’s modulus of the structure reaches 155.18 GPa, and its ultimate strength increases to 40.30 GPa. On the other hand, as the cross-sectional area of ​​the simulated nanostructure increases, the atomic interaction between the Si sample and the Fe nanoparticles decreases. Therefore, the values of Young’s modulus and the ultimate strength of the structure are decreased. Generally, the results of this simulation show Fe nanoparticles’ significant effect on the pristine Si sample’s mechanical properties, which can be used for industrial applications.

The liquid Fe-C alloy is the most important system in the metallurgical process and the molecular dynamics simulation were carried out to investigate the structure and properties of liquid Fe-C alloy using EAM and MEAM potential. The local structural order, transport properties and fluidity were analyzed. By comparison, the EAM potential is better than MEAM potential to simulate the properties of liquid Fe-C system. In the liquid state, the Fe-C alloy have a short-ranged ordered structure, accompanied by the transformation of Fe4C units to Fe6C units with the carbon content increasing. And the increase in carbon content could increase the complexity of the liquid structure. In terms of transport properties and fluidity, there is an inflection point when carbon content increases to 2 wt%. When the carbon content is less than 2%, the change of Fe atom transport performance is the main factor that leads to the increase of viscosity. On the contrary, when the carbon content is more than 2%, the transportation of C atom dominates.

In order to investigate how cutting parameters affect the nano-cutability of Ni-based high-temperature alloy GH4169, molecular dynamics (MD) simulations of the material have been conducted on a large-scale atomic molecular/massively parallel simulator (LAMMPS) for different cutting speeds and cutting depths. EAM potential is used between Ni, Fe and Cr, whereas Moses potential is used between the workpiece and the tool or between the tools. The results show that at the cutting depth of 1 nm, the chip shape has a tensile necking with increasing cutting speed; at the cutting depth of 3 nm, the shear line width increases with increasing cutting distance and there is an abrupt change in the evolution of both FCC and amorphous atoms at all cutting speeds. At the same cutting depth, the cutting area temperature increases with increasing cutting speed; at the same cutting speed, the cutting area temperature increases markedly with increasing cutting depth, too.The dislocation density of 1/6 Shockley with a cutting depth of 1 nm is higher than that of other depths at the same cutting speed,and the dislocation density of 1/6 Shockley is obviously positively correlated to cutting speeds at the same cutting depth.

The structure and dynamics of the Zr48Cu36Ag8Al8 alloy were investigated by molecular dynamics simulation method using the embedded atom method (EAM) and tight-binding (TB) potentials. Total structure factors and pair distribution functions calculated from both potentials are in good agreement with the reported experimental data. The glass transition temperature was determined more easily by using the Wendt-Abraham parameter, which we modified with small changes. The fraction of 1551-bonded pairs and Zr-, Cu-, Ag- and Al-centered icosahedral-like clusters increased with decreasing temperature. High fractions of Cu-, Ag- and Al-centered perfect icosahedra and Zr-centered icosahedra-like clusters were detected in both supercooled liquids and glasses. The critical temperature was determined to be ~760.65 K from mode coupling theory. Although the results for the EAM and TB potentials were largely consistent with the experiment, aggregations were detected in the Ag and Al atoms at low temperatures for the EAM potential.

Aluminum (Al) nanoparticles effects on the atomic behavior of Argon (Ar) fluid inside the zigzag nanochannel are described in this study. For this purpose, Molecular Dynamics (MD) approach is used with a LAMMPS package. Computationally, Ar base fluid and Ar Al nanofluid is modeled with Universal Force Field (UFF) and Embedded Atom Model (EAM). Total energy, density, velocity, and temperature profiles for the atomic behavior of base fluid/nanofluid are presented. Results show that the Al nanoparticles cause increasing of the density, velocity, and temperature profiles value to 0.106 atom/A3, 0.044 A/ps, and 551.02 K, respectively. So we conclude the Al nanoparticles adding to Ar atoms in non-ideal (zigzag) nanochannel can change atomic behavior of the base fluid effectively and optimize the Ar performance for heat/mass transfer applications.

A modified embedded-atom model (MEAM) is developed for cesium to reproduce its high-pressure phase transition and compared with the embedded-atom model (EAM) and the PBE (Perdew-Burke-Ernzerhof) functional. The MEAM reproduces successfully the high-pressure phase transition from body-centered cubic (bcc) structure to face-centered cubic (fcc) structure at 0 K in terms of formation energy as a function of pressure, and the evaluated compression curve agrees satisfactorily with the experimental observations reported in literatures. Though the EAM can also reproduce the high-pressure phase transition, it behaves much stiffer than experimental observations and is almost uncompressible below 0.2 GPa at 0 K. On the other hand, the PBE functional cannot reproduce the high-pressure phase transition and the calculated results become unstable under high pressure. Finally, the elastic constants, Poisson’s ratio, radial distribution function, lattice constant, vacancy formation energy, interstitial formation energy, and melting point are evaluated using molecular dynamics simulation based on the MEAM.

Molecular dynamics (MD) simulation-based studies of tensile test and structural evolution of Cu-5 at.% Zr alloy under asymmetric cyclic loading (i.e., ratcheting behavior) considering various stress ratios such as − 0.2, − 0.4 and − 0.6 for different temperatures, viz.≈ 100, 300 and 500 K have been performed using embedded atom model Finnis–Sinclair potential. According to obtained stress–strain response from MD calculation, Cu-5 at.% Zr alloy specimen is pristine in nature as sudden drop in stress just after yield stress and subsequent elastic type deformation are observed for this alloy. Predicted ratcheting strain by MD simulation for Cu-5 at.% Zr alloy varies from 4.5 to 5%. Significant increase in ratcheting strain has been observed with the increase in temperature. Slight reduction in crystallinity is identified at the middle of the each loading cycle from the performed radial distribution function analysis and cluster analysis.

The modified analytic embedded atom model (EAM) potentials considering farther neighbor atoms are improved for the noble metals (Ag, Au, Pt, Pd, Rh) and Cu. We not only adopt an end processing function and an enhanced smooth continuous condition for the pair potential, but also adjust the model parameters of multi-body potential by fitting a cohesive energy, a mono-vacancy formation energy, the Rose equation curve for the cohesive energy as a function of lattice parameter, a structure energy difference, elastic parameters and an equilibrium condition of crystal. The calculation results of structure energy differences misfit the experiment data for the noble metals and Cu in the unimproved EAM, because anyone of these differences have not been considered in the calculation of its model parameters. After the modification, the model showed better simulation results for the noble metals and Cu.

Models of mercury were constructed by molecular dynamics using the interparticle potential of the embedded atom model (EAM) at temperatures below 10 000 K and pressures below 2.5 GPa. The thermodynamic properties of the models were presented on the isobars of 0.5, 1.0, 1.5, 2.0, and 2.5 GPa. The compressibility factors Z = pV/(RT) were calculated; the coordinates of the inversion points of the Joule–Thomson coefficient below 5600 K were found from the positions of minima on the Z(p, T) isobars. At densities above 8–9 g/cm3, the results of simulation agreed well with experiment; at lower densities there were discrepancies associated with a loss of metal properties by real mercury. The behavior of the models was analyzed in the region of the van der Waals loop. The calculated critical temperature of mercury was found to be significantly overestimated relative to the experiment. Modeling the “meta-mercury” with the EAM potential with excluded embedded potential contribution gave better agreement with the equation of state of mercury at lower densities. The states with Z = 1 can be observed below 1.0 GPa. The calculated temperature of the inversion of the Joule–Thomson coefficient increased monotonically to 5600 K as the pressure increased to 2.5 GPa.

Lattice-switch Monte Carlo (LSMC) is a method for evaluating the free energy between two given solid phases. LSMC is a general method, being applicable to a wide range of problems and interatomic potentials . Furthermore it is extremely efficient, ostensibly more efficient than other existing general methods. Here we introduce a package, monteswitch , which can be used to perform LSMC simulations. The package can be used to evaluate the free energy differences between pairs of solid phases, including multicomponent phases, via LSMC for atomic (i.e., non-molecular) systems in the NVT and NPT ensembles. It could also be used to evaluate the free energy cost associated with interfaces and defects. Regarding interatomic potentials, monteswitch currently supports various commonly-used pair potentials, including the hard-sphere, Lennard-Jones, and Morse potentials , as well as the embedded atom model. However the main strength of the package is its versatility : it is designed so that users can easily implement their own potentials. Program summary Program Title: monteswitch Program Files doi: http://dx.doi.org/10.17632/zzy7jh9ynk.1 Licensing provisions: MIT Programming language: Fortran 95, MPI Nature of problem: Calculating the free energy difference between two solid systems. Solution method: Lattice-switch Monte Carlo (LSMC) [1] is a versatile and efficient method for evaluating the free energy difference between two solid phases. The package presented here allows LSMC simulations to be performed for a variety of interatomic potentials, including commonly-used pair potentials and the embedded atom model. Furthermore the package is designed so that users can easily implement their own potentials. The package supports LSMC simulations in the NVT and NPT ensembles, and can treat multicomponent systems. A version of the main program is included which is parallelised using MPI. This program parallelises the LSMC calculation by simulating multiple replicas of the system in parallel. External routines/libraries: To perform parallel simulations MPI is required (but MPI is not required to perform serial simulations). Restrictions: monteswitch cannot treat molecular systems, i.e., systems in which the particles exhibit rotational degrees of freedom, and is restricted to systems which can be represented within an orthorhombic supercell . Furthermore, the interatomic potential is ‘hard-coded’ in the sense that implementing a different potential requires that the package be recompiled. Additional comments: monteswitch includes programs to assist with the creation of input files and the post-processing of output files created by the main Monte Carlo programs. A user manual, a suite of test cases, a worked example, and a collection of plug-ins to implement various commonly-used interatomic potentials are also included with the package. [1] A.D. Bruce, N.B. Wilding & G.J. Ackland, Phys. Rev. Lett. 79 3002 (1997)

A new interatomic potential for graphite and graphene based on embedded atom method is proposed in this paper. Potential parameters were determined by fitting to the equilibrium lattice constants, the binding energy, the vacancy formation energy and elastic constants. The agreement between the calculated properties of graphite and experimental data is very good. In addition, the proposed potential quite accurately reproduces the surface energy of graphite and the binding energies of carbon atom in fullerene C60 and in SWNTs. The proposed potential is computationally more efficient than the existing widely used carbon potentials. It is intended for use in large-scale molecular dynamics simulations of carbon structures.

Slip transfer via sequential pile-up dislocations across grain boundaries (GBs) plays an important role in plastic deformation in polycrystalline face-centered cubic (FCC) metals. In this work, large scale concurrent atomistic-continuum (CAC) method simulations are performed to address the slip transfer of mixed character dislocations across GBs in FCC Ni. Two symmetric tilt GBs, a Σ3{111} coherent twin boundary (CTB) and a Σ11{113} symmetric tilt GB (STGB), are investigated using five different fits to the embedded-atom method (EAM) interatomic potential to assess the variability of predicted dislocation-interface reaction. It is shown that for the Σ3 CTB, two of these potentials predict dislocation transmission while the other three predict dislocation absorption. In contrast, all five fits to the EAM potential predict that dislocations are absorbed by the Σ11 STGB. Simulation results are examined in terms of several slip transfer criteria in the literature, highlighting the complexity of dislocation/GB interactions and the significance of multiscale modeling of the slip transfer process.

The stability of the body- and face-centered cubic lattices corresponding to the α and γ phases of Fe, respectively, as well as the transformation of one phase to the other were investigated by atomistic simulations. Two interatomic potentials were used: the embedded atom method (EAM) potential of Meyer and Entel and the bond order potential (BOP) developed by Muller et al. The suitability of the potentials for investigating structural transformations in Fe was verified using nonequilibrium free energy calculations and molecular dynamics simulations. The results showed that the EAM potential is capable of describing the bcc → fcc and fcc → bcc transformations whereas no transformation was observed for the computationally more expensive BOP potential with the simulation set up used.

This research work reviews the milling of copper using molecular dynamics (MD) simulation to study underlying core mechanisms experienced during the cutting process. The inconsistency in the machinability of one material relative to another is based on both physical and mechanical properties it possesses. Improved studies of the sub-surface mechanismsoccurring during cutting are required as it depicts a clearer picture for condition prediction. In this study, the classical molecular dynamics simulation was performed to investigate the deformation in the machining of copper. This approach employs the use of the Morse potential to represent the interatomic forces between the atoms of the copper work piece and the tool as well as the EAM potential between work piece atoms. Owing to the malleable and ductile nature of copper, the influence of some machining conditions on the mechanical properties was also analysed. Conditions such as thermodynamic form, energy and temperature were observed. Relations to strain effects and dislocations within the simulated copper block have been associated to force variation obtained during milling. This is seen from the gradual increase in energy and force correlations during simulations. Representation of the actual milling process was done to validate the results obtained from the simulation. From the results, it was found that the MD simulations provided an adequate representation of the sub-surface and surface effects experienced in the milling of copper. Further analysis into the tool chips and chip formation was also performed.

The embedded atom model (EAM) potentials are proposed, enabling the description of liquid gallium and tin under conditions typical to shock compression. The potentials reported earlier to describe metals under pressures close to normal and the experimental data on shock compression are used. Series of models are constructed 2000 or 2048 atoms in size in a basic cube at compression ratios Z up to 0.5 of the initial volume under pressures up to 385 GPa and temperatures up to 32000 K. These potentials give a satisfactory description of liquid gallium and tin under shock compression. The thermodynamic properties of the metals at compression ratios up to 0.5 and temperatures up to 20000 K are calculated and given in tabular form. In the case of gallium, a small compression of models with normal density decreases the total energy at 300, 500, 15000, and 20000 K, and, for tin, this effect is observed only at 20000 K. The energy and pressure of the FCC metal models are markedly lower than those of noncrystalline models. The cold pressure for the states at temperatures between 0 and 298 K is evaluated. The EAM potential of tin leads to a lowering of the cold pressure of an FCC lattice with respect to the amorphous phase at Z < 0.75.

The molecular dynamics simulations with embedded atom model (EAM) potential had performed to investigate the icosahedral network connectivity in Mg70Zn30 alloy. The microstructure was detected with a new precise method of largest standard cluster analysis. It was validated that the EAM potential is succeed in reflecting the objective physical nature of Mg-Zn alloy systems. Results shows that large amount of nanoclusters consist of ICOIs, which shows large connectivity variations, formed in the system with decreasing temperature. And the ICOIs connect over extended range act as backbone for a networked structure.

Interatomic potentials based on neural-network machine learning (ML) approach to address the long-standing challenge of accuracy versus efficiency in molecular-dynamics simulations have recently attracted a great deal of interest. Here, utilizing Pd-Si system as a prototype, we extend the development of neural-network ML potentials to compounds exhibiting various types of bonding characteristics. The ML potential is trained by fitting to the energies and forces of both liquid and crystal structures first-principles calculations based on density-functional theory (DFT). We show that the generated ML potential captures the structural features and motifs in $\mathrm{P}{\mathrm{d}}_{82}\mathrm{S}{\mathrm{i}}_{18}$ and $\mathrm{P}{\mathrm{d}}_{75}\mathrm{S}{\mathrm{i}}_{25}$ liquids more accurately than the existing interatomic potential based on embedded-atom method (EAM). The ML potential also describes the solid-liquid interface of these systems very well. Moreover, while the existing EAM potential fails to describe the relative energies of various crystalline structures and predict wrong ground-state structures at $\mathrm{P}{\mathrm{d}}_{3}\mathrm{Si}$ and $\mathrm{P}{\mathrm{d}}_{9}\mathrm{S}{\mathrm{i}}_{2}$ composition, the developed ML potential predicts correctly the ground-state structures from genetic algorithm search. The efficient ML potential with DFT accuracy from our study will provide a promising scheme for accurate atomistic simulations of structures and dynamics of complex Pd-Si system.

The adhesion feature of graphene on metal substrates is important in graphene synthesis, transfer and applications, as well as for graphene-reinforced metal matrix composites. We investigate the adhesion energy of graphene nanosheets (GNs) on iron substrate using molecular dynamic (MD) simulations. Two Fe&ndash, C potentials are examined as Lennard&ndash, Jones (LJ) pair potential and embedded-atom method (EAM) potential. For LJ potential, the adhesion energies of monolayer GN are 0.47, 0.62, 0.70 and 0.74 J/m2 on the iron {110}, {111}, {112} and {100} surfaces, respectively, compared to the values of 26.83, 24.87, 25.13 and 25.01 J/m2 from EAM potential. When the number of GN layers increases from one to three, the adhesion energy from EAM potential increases. Such a trend is not captured by LJ potential. The iron {110} surface is the most adhesive surface for monolayer, bilayer and trilayer GNs from EAM potential. The results suggest that the LJ potential describes a weak bond of Fe&ndash, C, opposed to a hybrid chemical and strong bond from EAM potential. The average vertical distances between monolayer GN and four iron surfaces are 2.0&ndash, 2.2 &Aring, from LJ potential and 1.3&ndash, 1.4 &Aring, from EAM potential. These separations are nearly unchanged with an increasing number of layers. The ABA-stacked GN is likely to form on lower-index {110} and {100} surfaces, while the ABC-stacked GN is preferred on higher-index {111} surface. Our insights of the graphene adhesion mechanics might be beneficial in graphene growing, surface engineering and enhancement of iron using graphene sheets.

We present a package to simulate long-term diffusive mass transport in systems with atomic scale resolution. The implemented framework is based on a non-equilibrium statistical thermo-chemo-mechanical formulation of atomic systems where effective transport rates are computed using a kinematic diffusion law. Our implementation is built as an add-on to the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code, it is compatible with other LAMMPS’ functionalities, and shows a good parallel scalability and efficiency. In applications involving diffusive mass transport, this framework is able to simulate problems of technological interest for exceedingly large time scales using an atomistic description, which are not reachable with the state-of-the-art molecular dynamics techniques. Several examples, involving complex diffusive behavior in materials, are investigated with the framework. We found good qualitative and quantitative comparison with known theories and models, with Monte Carlo methods, as well as with experimental results. Thus, our implementation can be used as a tool to understand diffusive behavior in materials where experimental characterization is difficult to perform. Program summary Program Title: MXE package Program Files doi: http://dx.doi.org/10.17632/s2mhjb8hyk.1 Licensing provisions: GNU GPLv3 Programming language: c++ Supplementary material: The user manual and examples are provided along with the source code. External routines: MPI, LAMMPS, 12 December 2018 ( http://lammps.sandia.gov/ ) Nature of problem: The simulation of diffusive mass transport in atomistic systems, involving vacancies, interstitials and solute atoms, is often challenging due to the exceedingly large time scale involved in these slow processes. Thus, molecular dynamics, a preferred technique to simulate atomistic systems, is not capable of accessing these long-term diffusive timescale, hindering its application to this kind of phenomena. Solution method: We present an implementation for simulating diffusive mass transport in atomic system. The methodology is based on two main pillars: (i) A non-equilibrium thermodynamic formulation of atomic system (Venturini et al., 2014); and (ii) Fokker–Planck master equation that encompasses the time evolution of the atomic molar fraction field in atomic systems (Ponga and Sun, 2018). The proposed implementation is built as a user package of the popular Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The implementation is flexible and robust, shows good parallel scalability and efficiency, and is compatible with all features available in LAMMPS. Additional comments including restrictions and unusual features: Unique features of the implementation involve the simulation of vacancy, interstitial, solutes and substitutional alloys for exceedingly large time scales. The current implementation in this package is limited to the Embedded Atom Model potentials. References [1] G. Venturini, K. Wang, I. Romero, M. Ariza, M. Ortiz, Journal of the Mechanics and Physics of Solids 73 (2014) 242–268. [2] M. Ponga, D. Sun, Modeling and Simulation in Materials Science and Engineering 26 (2018) 035014.

One of the recurring anomalies in the hydrogen induced fracture of high strength steels is the apparent disconnect between their toughness and uniaxial tensile strength in identical hydrogen environments. Here we propose, supported by detailed atomistic and continuum calculations, that unlike macroscopic toughness, hydrogen-mediated tensile failure is a result of a fast-fracture mechanism. Specifically, we show that failure originates from the fast propagation of cleavage cracks that initiate from cavities that form around inclusions such as carbide particles. The failure process occurs in two stages. In stage-A, hydrides rapidly form around the roots of stressed notches on the cavity surfaces with hydrogen fed from the hydrogen gas within the cavity. These hydrides promote cleavage fracture with the cracks propagating at >100 ms^(-1) until the hydrogen gas in the cavity is exhausted. Predictions of this hydrogen-assisted crack growth mechanism are supported by atomistic calculations of binding energies, mobility barriers and molecular dynamics calculations of the fracture process. Typically, cracks grow by less than 1 μm via this hydrogen-assisted mechanism and thus insufficient to cause macroscopic fracture of the specimen. However, this stage is then followed by a stage-B process where these fast propagating cracks can continue to grow, now in the absence of hydrogen supply, given an appropriate level of remote tensile stress. This is surprising because the fracture energy is now that of Fe in the absence of H and cleavage fracture requires opening tractions on the order of 15 GPa to be generated. Thus, fracture is usually precluded due to plasticity around the crack-tip. Here we show via macroscopic continuum crack growth calculations in a rate dependent elastic-plastic solid with fracture modelled using a cohesive zone that cleavage is possible if the crack propagates fast enough. This is because strain-rates at the tips of fast propagating cracks are sufficiently high for the drag on the motion of dislocations resulting from phonon scattering to limit plasticity. This combined atomistic/continuum model is used to explain a host of well-established experimental observations including (but not limited to): (i) insensitivity of the strength to the concentration of trapped hydrogen; (ii) the extensive microcracking in addition to the final cleavage fracture event and (iii) the higher susceptibility of high strength steels to hydrogen embrittlement. Importantly, we also show that the stage-A hydrogen-assisted fracture process only occurs in certain crystallographic orientations with crack-tip plasticity processes, such as twinning, blunting cracks in other orientations. This inhibits the fast-fracture mechanism in a macroscopic toughness on a polycrystalline material and thus explains the apparent contradiction between the hydrogen-assisted macroscopic toughness and tensile strength of steels.

We develop an embedded-atom method (EAM) model to perform classical molecular-dynamics computer simulations of a model of Zr-Ni-Al ternary melts, based on the existing binary ones. The EAM potential is validated against a broad range of experimental data for the liquid melt, including both static-structure factors and dynamical data on the mass-transport coefficients. We use our simulation model to address the structural and dynamical changes induced by a systematic replacement of Zr by Al in ${\mathrm{Zr}}_{75\ensuremath{-}x}{\mathrm{Ni}}_{25}{\mathrm{Al}}_{x}\phantom{\rule{4pt}{0ex}}(x=0--30)$ ternary alloys. We find strong chemical-ordering effects exhibited as the locally preferred structure when the Al-concentration ${c}_{\text{Al}}$ is increased. Along with the chemical effects, effective-power-law relations are found between the self-diffusion coefficients in the melts, with an exponent that monotonically decreases with increasing Al concentration. The associated Stokes-Einstein relation between diffusivity and viscosity breaks down at higher temperature upon Al addition. We also address the influence of Al admixture on the vibrational spectrum of the melt. With increasing ${c}_{\text{Al}}$, sound waves move faster, and an optical vibrational mode is found.

The idea that shape and structure determines functionality is one of the leiv-motifs that drives research and applications on fields such as catalysis and plasmonics. The growth and stability of metallic clusters is extensively discussed through faceting and energy minimization mechanisms, respectively. Facet truncations on the regular Mackay-icosahedron (m-Ih) give rise to two sub-families exhibiting five-fold symmetry and external decahedral shape. Such successive truncations made to the regular m-Ih, led to a decahedral motif called 'Decmon' (Montejano's decahedron). This structure expose facets (111) and (100), that after a total energy minimization through molecular dynamics simulations using the embedded atom model, proved to be thermally stable. This result has been confirmed by using nano-thermodynamics. The surface energy competition between the (111) and (100) facets explains its stability at some given cluster sizes, and this truncation path permits to glimpse the potential energy surface in the growth path of nanoparticles from the decahedral (s-Dh) to icosahedral (m-Ih) structures.

In the paper, the process of Ti6–Al4–V aging phase transition and diffusion bonding was studied by molecular dynamics method. The EAM potential combined with more potential was employed to deal with the interaction between the atoms of Ti–Al–V ternary alloy. The radial distribution function of Ti6–Al4–V and the relative content of different crystal structures were analyzed. The results show that the structural changes of Ti6–Al4–V in the aging phase transition are mainly manifested in the new phase of metastable phase. In the process of diffusion, the titanium atoms near the interface are mainly diffused, and vanadium atomic diffusion is secondary, while aluminum atom is relatively few. Under the same conditions, the diffusion connection width and thermal insulation temperature are in a good linear relationship. In addition, the diffusion coefficient of titanium is exponentially related to the temperature of heat preservation. The simulation results are good agreement with the experiment.

In order to explore how cutting parameters affect the evolution of subsurface defect of single crystal copper during nanocutting process, a nanocutting model is constructed based on LAMMPS; the nanocutting process of single crystal copper is investigated through molecular dynamics (MD) simulations for different cutting speeds and cutting depths, using EAM potential between Cu atoms and Morse potential between Cu atoms and the tool atoms. The results show that at the same cutting depth, cutting speed does not make much difference to the subsurface dislocation form; at the same cutting speed, cutting depth makes a great difference to the subsurface dislocation form and it also affects the crystal structure type of the defect layer very significantly. Under any cutting parameters, the dislocation form of 1/6 is dominant. With the increase of cutting speed and cutting depth, the dislocation of 1/6 and 1/3 of subsurface layer increased obviously, and the length of dislocation line also increased.

Barrier size influences on the thermal behavior of Ar/Cu nanofluid are reported in this simulation work. Molecular dynamics method is implemented with a large molecular/atomic parallel simulator. Furthermore, Ar/Cu nanofluid is simulated with Universal Force Field (UFF) and Embedded Atom Model (EAM) force fields and these force fields are appropriate to our thermal study. For the thermal behavior of this nanofluid, we record the physical parameters like total energy, thermal conductivity of nanofluid, density, the number of nanofluid atoms in the gas phase, and atomic temperature. Simulation results show that atomic structures have thermal stability with −318 eV value for total energy parameter. Physically, the atomic barrier causes the atomic phase transition phenomena to happen in a shorter time. Numerically, this parameter varies from 0.61 ns to 0.55 ns when the Platinum (Pt) barriers height increases from 5 A to 10 A. We calculated that the maximum density of nanofluid atoms reaches to 0.00025 Atom/A3 by atomic barriers enlarging. So, we conclude that, by increasing the received heat flux with Ar/Cu nanofluid, the thermal conductivity converged in shorter simulation time. Numerically, the thermal conductivity of simulated structures converges to 0.016400 W/m.K after 0.63 ns.

The validity of Stokes−Einstein (SE) relations obtained from both slip and stick boundary conditions has been investigated for an extending temperature range approximately 250 K from the melting points of liquid Fe, Co and Ni using Dzugutov scaling scheme for transport coefficients. The basic ingredients of Dzugutov scaling scheme are the temperature dependent effective hard-sphere (HS) diameter, σ(T), and the excess entropy, Sex(T). Sex is calculated considering both two (S2) and many body approximations (ST) of liquid atoms. For both ingredients, we have applied variational modified hypernetted chain (VMHNC) integral equation theory in conjunction with both Brettonet−Silbert (BS) pseudopotential and many body potential obtained from embedded atom method (EAM). Calculated transport coefficients using the combination of EAM and ST are in better agreement with available literature values than any other applied combinations. We observe that SE relation holds for the studied representative systems when the combination of EAM potential and ST has been considered.

We use quantum mechanical ab initio simulation to inform a model which predicts the structures of coherent Cu nanoprecipitates that are thought to form in low-alloy reactor pressure vessel (RPV) steels. Using density functional theory (DFT) we calculated the interfacial energy densities of {1 0 0}, {1 1 0}, {1 1 1}, {2 1 0}, {2 1 1} and {2 2 1} orientated Fe-Cu interfaces. These energy density values were used in an optimisation model to predict low energy Cu nanoprecipitate geometries for nominal radii ranging from 1 to 5 nm. Strain states parallel to the Fe-Cu interface were calculated using an embedded atom method (EAM) potential for similarly sized Cu nanoprecipitates. Fe-Cu interfacial energy densities under equivalent strains were calculated using DFT allowing comparison with the predictions of the EAM potential. The DFT calculations revealed the lowest energy Fe-Cu interface orientation to be the {1 1 0}. Accordingly, the geometry prediction optimisations found that regardless of size the predicted Cu nanoprecipitate surface geometries were dominated by the {1 1 0} orientation. Notably, as the Cu nanoprecipitates increased in size the ratio of the surface made up of non-{1 1 0} orientations was observed to proportionally increase. This allows the nanoprecipitate to take a more spherical form so reducing its total surface area. Additionally, the Fe-Cu interface strains predicted by the EAM potential for all Cu nanoprecipitate radii are sufficiently small that they do not significantly alter the calculated interfacial energy density values. This finding suggests interfacial strain does not play a significant role in determining the morphology of Cu nanoprecipitates.

In this work, we study the distribution of potential energies for the embedded atom model (EAM), commonly associated with monoatomic metals, in nanoscopic systems of the order of tens of particles. Classical molecular dynamics simulations in the microcanonical ensemble, both in solid and liquid phases, were used to produce samples of potential energy at different total energies. We characterize the shape of these fluctuations of potential energy and, in this context, we propose a model for the configurational density of states (CDOS) capable of describing the melting phase transition of a nanoscopic system. Our results show the shape of the fluctuations outside and within the range of the solid–liquid phase transition, and demonstrate the accuracy of the CDOS model for EAM systems.

Anisotropic core-shell model of a nano-grained polycrystal is extended to estimate the effective elastic stiffness of several metals of hexagonal crystal lattice symmetry. In the approach the bulk nanocrystalline material is described as a two-phase medium with different properties for a grain boundary zone and a grain core. While the grain core is anisotropic, the boundary zone is isotropic and has a thickness defined by the cutoff radius of a corresponding atomistic potential for the considered metal. The predictions of the proposed mean-field model are verified with respect to simulations performed with the use of the Large-scale Atomic/Molecular Massively Parallel Simulator, the Embedded Atom Model, and the molecular statics method. The effect of the grain size on the overall elastic moduli of nanocrystalline material with random distribution of orientations is analyzed.

In this computational work, we focus on spherical barrier effects on the thermal behaviour of Ar/Cu nanofluid with molecular dynamics simulation. LAMMPS software is implemented in our study with Universal Force Field and Embedded Atom Model force field for various atomic structures in the simulation box. The thermal behaviour study of Ar/Cu nanofluid is done with physical parameters calculations such as atomic temperature, total energy, number of nanofluid atoms at gas phase, radial distribution function, and thermal conductivity of Ar/Cu nanofluid. By atomic barrier adding to our simulated plates, the atomic phase transition occurs in fewer time steps. Numerically, phase transition in the simulated nanofluid occurs in 610,000-time steps by Pt spherical barriers simulation (with 15 A radius). By increasing the atomic barrier size, the number of nanofluid atoms in which phase transition occur in them is increased. From these simulations results, we conclude that, heat flux in Ar/Cu nanofluid increases but thermal conductivity of the foremost constant. Numerically, the thermal conductivity of Ar/Cu nanofluid reaches to 0.016 W/m.K by atomic barrier radius increasing to 15 A.

The fundamental mechanism of the precipitation kinetics and stability of nano-sized Cu-precipitates are crucial to the development of ultra-high strength low carbon ferritic steels. The effects of Al on the formation and stabilization of B2 Cu-rich precipitates in Fe–Cu based steels were studied using experimental method combining the first-principles calculations and molecular dynamics simulations. With increasing aging time, the Cu-rich particles with B2 structure precipitated in the ferritic matrix with cube-on-cube and coherent relationship, and Al addition leads to a relatively higher precipitation hardening effect. The first-principle calculations indicate that the metastable B2 FeCu phase has relatively higher mixing energy and small lattice mismatch with the ferritic matrix, and the addition of Al leads to the lower mixing energy of B2 precipitates and the B2 structure Fe(CuAl) compound possesses more smaller lattice mismatch with ferritic matrix. To better understanding the effect of Al on the evolution process of Cu-rich particles, it is essential to investigate the migration and clustering process of Cu atoms during the isothermal tempering at the atomic scale. To this end, we first developed a new interatomic potential of Fe–Cu–Al using the force-matching method based on ab initio calculations, then the formation and evolution of Cu clusters in the Fe–Cu–Al ternary were studied using molecular dynamics method with the new EAM potential. The simulation results indicate that Al addition promotes the clustering of Cu atoms due to the attractive interaction between Cu and Al atoms which enhances nucleation rate of the Cu-rich precipitates.

The thermodynamic and kinetic behaviors of gold nanoparticles confined between two-layer graphene nanosheets (two-layer-GNSs) are examined and investigated during heating and cooling processes via molecular dynamics (MD) simulation technique. An EAM potential is applied to represent the gold–gold interactions while a Lennard–Jones (L–J) potential is used to describe the gold–GNS interactions. The MD melting temperature of 1345 K for bulk gold is close to the experimental value (1337 K), confirming that the EAM potential used to describe gold–gold interactions is reliable. On the other hand, the melting temperatures of gold clusters supported on graphite bilayer are corrected to the corresponding experimental values by adjusting the eAu–C value. Therefore, the subsequent results from current work are reliable. The gold nanoparticles confined within two-layer GNSs exhibit face center cubic structures, which is similar to those of free gold clusters and bulk gold. The melting points, heats of fusion, and heat capacities of the confined gold nanoparticles are predicted based on the plots of total energies against temperature. The density distribution perpendicular to GNS suggests that the freezing of confined gold nanoparticles starts from outermost layers. The confined gold clusters exhibit layering phenomenon even in liquid state. The transition of order–disorder in each layer is an essential characteristic in structure for the freezing phase transition of the confined gold clusters. Additionally, some vital kinetic data are obtained in terms of classical nucleation theory.

Gold (Au) nanoparticles are widely used in diagnosing cancer, imaging, and identification of therapeutic methods due to their particular quantum characteristics. This research presents different types of aqueous models and potentials used in TIP3P, to study the effect of the particle size and density of Au clusters in aquatic environments; so it can be useful to facilitate future investigation of the interaction of proteins with Au nanoparticles. The EAM potential is used to model the structure of gold clusters. It is observed that in the systems with identical gold/water density and different cluster radii, gold particles are distributed in aqueous environment almost identically. Thus, Au particles have identical local densities, and the root mean square displacement (RMSD) increases with a constant slope. However in systems with constant cluster radii and different gold/water densities, Au particle dispersion increases with density; as a result, the local density decreases and the RMSD increases with a larger slope. In such systems, the larger densities result in more blunted second peaks in gold–gold radial distribution functions, owing to more intermixing of the clusters and less FCC crystalline features at longer range, a mechanism that is mediated by the competing effects of gold–water and gold–gold interactions.

The conductive pastes containing Ag particles are used for patterning the electrodes of electronic devices such as solar cells and touch screen panels. Although Cu@Ag type metal particles have been tried as a substitute instead of Ag for cost reduction, the dewetting of Ag from Cu core during the processes has limited the use of Cu as a core metal. In this work, to investigate the Cu-Ni alloys as the core metal, we analyze the surface structures of Cu-Ni alloys and measure the compatibility between Ag and Cu-Ni alloys as wells as Cu and Ni by calculating the contact angles of Ag droplet on the metal surfaces using molecular dynamics simulations. As the Ni content of Cu-Ni alloys increases, the contact angle decreases: the contact angles for Cu, Cu 3 Ni, CuNi, CuNi 3 , and Ni are 69.6, 52.6, 50.5, 45.1, and 8.9°, respectively. Therefore, the wettability of Ag on the Cu-Ni alloys is improved with the Ni content in the Cu-Ni alloys. This result indicates that the Cu-Ni alloys could be good candidates as the core metal to be used in the metal particles for the conductive pastes.

A molecular dynamic (MD) simulation has been performed to study the creep behavior and structural evaluation during creep process of nano-joint of nano-crystalline (NC) Ni and Fe–Ni–Cr alloy (18 at.% Cr, 8 at.% Ni and rest Fe) using EAM potential. A simulation box of 14.4 × 14.4 × 14.4 nm dimension having 254,407 atoms is taken for performing MD simulation. MD simulation of creep of this nano-joint has been performed for different temperatures and different applied load. Centro-symmetry parameter (CSP) analysis, common neighbor analysis (CNA), radial distribution function (RDF), Wigner–Seitz defect analysis, and Voronoi cluster analysis (VCs) have been performed to study structural evolution during creep process. Dislocation also plays a role along with the grain boundary diffusion at least for primary and secondary regime of creep process of this nano-joint between NC Ni and Fe–Ni–Cr alloy. The average displacement of the atoms in the regions (±1 nm, ±2 nm, and ±3 nm) adjacent to the interface during creep process is calculated using traction and separation method to study the atomic movement near the interface. The atoms are observed to be displaced more which are nearer to the interface during creep of this nano-joint system. Keywords: Molecular dynamics, Creep, Interface, Nano-joint, Voronoi polyhedra

Structural and transport properties of the liquid Al80Cu20 alloy have been investigated performing molecular dynamics simulations using a new parametrization of modified embedded atom model (MEAM) potential method retained to the available ab initio molecular dynamics (AIMD) and experimental data. Local atomic structural changes, including chemistry and topology, have been studied and discussed with the literature data. Strong chemical bonding of unlike atoms in comparison to like-ones is found and confirmed by the available literature data. High degree of topological complexity and icosahedron-like type atomic clusters of increasing abundance with temperature decrease are observed, and their influence on short-range chemical ordering as well as transport properties have been defined. Almost perfect agreement between experimental data and the presented MEAM-MD simulations has been registered for the self-diffusion coefficient of Cu atoms in comparison to significant underestimation of experimentally determined inter-diffusion coefficient of the liquid Al80Cu20 alloy. Viscosities simulated, using two MD-based methods, exhibit a slight overestimation of experimental data.