Embedded Atom Model Research Articles

Molecular Dynamics Model of Liquid Tin in the Scheme of the Embedded Atom Model

Molecular Dynamics Model of Liquid Tin in the Scheme of the Embedded Atom Model

The interplay between size, shape, and surface segregation in high-entropy nanoalloys.

The respective influences of particle shape and size on the energetic stability of five-component multimetallic nanoparticles have been computationally investigated for AlCuFeCrNi and AuCuPdNiCo mixtures at equiconcentration. Using available embedded-atom model potentials, exchange Monte Carlo simulations possibly assisted with systematic quenching, we explore tools to approach ideal phase equilibrium in such high-entropy nanoalloys. In particular, we show how deviations to ideal solid solution behaviors can be characterized using percolation analyses, and how the contribution of alloying fluctuations at finite temperature can be inferred to evaluate the entropy of mixing in such nonideal cases. An approximation to the entropy of mixing based on pair correlations only is also found to capture the behavior of the thermodynamical mixing entropy quite well, and can be used as an order parameter of mixing. While the AlCuFeCrNi mixture appears to mix reasonably well in all cases considered, cobalt and nickel segregate significantly in AuCuPdNiCo nanoparticles, deviating strongly from ideal random mixtures. A simple Gaussian regression model applied to a coarse distribution of concentrations is found to correctly predict conditions for optimising the mixing thermodynamical properties of the miscible AlCuFeCrNi nanoparticle.

Computer simulation of AlCoCuFeNi high-entropy alloy thin film deposition and crystallization

The processes of deposition and crystallization of high-entropy AlCoCuFeNi alloy thin film on a substrate of silicon (100) are studied by classical molecular dynamics simulation. Total simulation time reaches 50 ns. The embedded atom model is used to describe the interaction among Al–Co–Cu–Ni–Fe. Interaction between the atoms of Al, Co, Cu, Fe, Ni, and the Si substrate is described using the Lennard–Jones potential, and the interaction between the silicon atoms was modeled using the Stillinger–Weber potential. It is found that at the first stage of deposition small clusters are formed and the process of crystallization starts after ~ 5 ns of simulation, at the characteristic sizes of clusters of about 2 nm. At the end of the simulation, after the 50 ns of modeling, the simulated film contains a face-centered cubic phase, a body-centered cubic phase, a hexagonal close-packed phase, and an amorphous phase. An analysis of the radial distribution of atoms makes it possible to determine the distances between the nearest neighbors and estimate the lattice parameters of these phases.

Extended Analytic Embedded-Atom Model for BCC Tantalum and Its Application to Determination of Gibbs Free Energy and Thermal Equation of State

Extended Analytic Embedded-Atom Model for BCC Tantalum and Its Application to Determination of Gibbs Free Energy and Thermal Equation of State

An embedded-atom method potential for studying the properties of Fe-Pb solid-liquid interface

A new interatomic potential for Fe-Pb binary system is developed in the framework of an embedded atom model using the force-matching method. Compared with the ab initio calculations and experiment values, the developed Fe-Pb EAM potential can accurately describe the ground state, defects and liquid properties of crystal and Fe-Pb solid-liquid interface, such as equation of state, vacancy and interstitial formation energies, adsorption and escape energies, melting point, radial distribution function and density at high temperature. High accuracy and feasibility of the developed Fe-Pb EAM potential can provide the further reliable studies on the corrosion behavior of liquid Pb on steels used in complicate environment of the irradiation, high temperature, pressure in nuclear reactors.

Experimental and theoretical examination of shock-compressed copper through the fcc to bcc to melt phase transitions

Recent studies show a face-centered cubic (fcc) to body-centered cubic (bcc) transformation along the shock Hugoniot for several metals (i.e., Cu, Au, and Ag). Here, we combine laser-shock compression of Cu foils on nanosecond timescales with in situ x-ray diffraction (XRD) to examine the microstructural changes with stress. We study the fcc phase and the phase transition from fcc to bcc (pressures greater than 180 GPa). Textural analysis of the azimuthal intensities from the XRD images is consistent with transformation into the bcc phase through the Pitsch-distortion mechanism. We use embedded atom model molecular dynamics simulations to determine the stability of the bcc phase in pressure–temperature space. Our results indicate that the bcc phase is stabilized only at high temperatures and remains stable at pressures greater than 500 GPa.

Numerical study of obstacle effect on atomic behavior of argon fluid flow inside a nanochannel with molecular dynamics approach

Various fluids are implemented for mass/heat transfer procedures in industrial applications. These structures' behavior inside the metallic nanochannels (NCs) in the presence of the obstacle was described. To this end, the Molecular Dynamics Simulation (MDS) is performed using the LAMMPS package. The various atomic forces in defined structures are defined using Universal Force Field (UFF) and Embedded Atom Model (EAM). In addition, physical parameters such as temperature (T), potential energy (PE), Radial Distribution Function (RDF), profiles of density (D)/velocity(V)/T, position histogram, trajectory lines, and interaction energy are reported for description of nanofluid (NF) flow. MDS results display the equilibrium of Ar (as fluid) and Pt (as NC) in the presence of obstacles after t = 20 ns. Also, our simulations predict that the obstacles increase/decrease the average values of fluid adsorption/mobility inside the NC.

The atomic obstacle size influence on the Hydrogen flow inside a nanochannel: A molecular dynamics approach to predict the fluid atomic arrangements

In the current computational work, the atomic behaviour of Hydrogen (H) atoms (as fluid) inside 2D Platinum (Pt) nanochannel (NC) in the presence of obstacles is described using molecular dynamics simulation (MDS) for clinical applications. This simulation method is reported by temperature (T), total energy, profiles of density/velocity/T and interaction energy of simulated compounds. Computationally, a fluid-NC system modelled with Universal Force Field (UFF) and Embedded Atom Model (EAM) potentials (force-fields). MD outputs indicated the potential energy of samples converged to a negative amount after 5 ns. This physical behaviour shows the stability of the defined system at T=300 K. Furthermore, the simulation results show the atomic behaviour of H fluid optimized by atomic obstacle radius optimizing. By using NC with an obstacle, the interaction energy between fluid atoms and NC walls reach -40.44 eV and by this process occur, mass transfer phenomenon optimized for clinical aims.

Atomistic origin of nano-silver paracrystalline structure: molecular dynamics and x-ray diffraction studies

Classical molecular dynamics (MD) and x-ray diffraction (XRD) have been used to establish the origin of the paracrystalline structure of silver nanoparticles at the atomic scale. Models based on the face-centred cubic structure have been computer generated and their atomic arrangements have been optimized by the MD with the embedded-atom model (EAM) potential and its modified version (MEAM). The simulation results are compared with the experimental XRD data in reciprocal and real spaces, i.e. the structure factor and the pair distribution function. The applied approach returns the structural models, defined by the Cartesian coordinates of the constituent atoms. It has been found that most of the structural features of Ag nanoparticles are better reproduced by the MEAM. The presence of vacancy defects in the structure of the Ag nanoparticles has been considered and the average concentration of vacancies is estimated to be 3 at.%. The average nearest-neighbour Ag–Ag distances and the coordination numbers are determined and compared with the values predicted for the bulk Ag, demonstrating a different degree of structural disorder on the surface and in the core, compared to the bulk crystalline counterpart. It has been shown that the paracrystalline structure of the Ag nanoparticles has origin in the surface disorder and the disorder generated by the presence of the vacancy defects. Both sources lead to network distortion that propagates proportionally to the square root of the interatomic distances.

Applying Simple Liquids Theory to Systems with the Potential of the Embedded Atom Model

Applying Simple Liquids Theory to Systems with the Potential of the Embedded Atom Model

Thermal analysis of hydration process in the vicinity of the Copper matrix using molecular dynamics simulation for application in thermal engineering

In this computational work, the Tetrahydrofuran (THF) hydration process in the vicinity of the Copper (Cu) matrix was reported by the molecular dynamics simulation (MDS). Our MDS outcomes are described with various physical parameters like total energy (TE), number of the atomic cage, hydrate layers, and enthalpy value. This study represents all structures by DREIDING, Universal Force Field (UFF), and Embedded Atom Model (EAM) with the atomic arrangement. Computational outcomes display that the TE of samples is converged to a constant value after t=100 ns; this computation indicates the physical stability at a defined initial condition. The temperature (T) increase in simulated structures causes an increase in the mobility of atoms in the MD box. This process decreases the atomic order in the simulated mixture, and so the hydration process is weakened. Numerically, with T enhancement from 260 K to 290 K, atomic cages and hydrate layers decrease from 31 to 16 and 4 to 2, respectively. On the other hand, pressure (P) increasing causes atomic interaction to enlarge in defined systems. This interaction enlarges the cause of atomic order improvement in the MD box. Also, as the P increased from 0 to 50, the number of cages detected in the simulation box increased from 31 to 39. So, the T reduction and increase in the initial P cause an effective hydration process in the MD box. Also, the simulation results show that at 0 bar P, with increasing T from 260 to 290 K, the system’s enthalpy decreases from 21.21 kcal/mol to 16.67 kcal/mol. On the other hand, at 260 K, increasing P from 0 to 50 bar, the system’s enthalpy enhances from 21.21 kcal/mol to 25.48 kcal/mol. These calculations show that the hydration process occurs effectively by initial condition manipulation, which can be important for various purposes such as oil industry applications.

MOLECULAR DYNAMICS SIMULATION OF COHESIVE ENERGIES AND ITS CORRESPONDING LATTICE PARAMETER OF SOME NANOCRYSTALS

Bulk solids have a microstructure that differs significantly from nanoscale materials. In modern era, new devices are always produced at nano-scale level and existing ones are quantized to fit the global demand. To achieve this, there is a need to understand the behaviour of materials at atomic level. As a result, examining the properties of nanoparticles can help in understanding the nature of small-scale material behavior. The cohesive energy and lattice constant are essential physical quantities that can be used to predict other material properties. In this research, the equilibrium cohesive energies and its corresponding lattice constants of three nanosized crystals (Al, Cu and Ni), were investigated using molecular dynamics simulation method with a semi-empirical embedded atom model (EAM) potential function. The simulated results reveal that the three nanocrystals’ lattice constant match the experimental data. Besides, Al, Cu and Ni have cohesive energies of -3.40 eV, -3.55 eV, -4.44 eV respectively. Cu’s cohesive energy differs from experimental data unlike Al and Ni. The findings in the current research are in good agreement with those obtained utilizing the First principle calculation method.

The computational study of microchannel thickness effects on H2O/CuO nanofluid flow with molecular dynamics simulations

Microchannels are promising structures for the different processes such as mass and heat transfer processes. Previous researches indicated the atomic behavior of nanofluids in these structures improved appreciably. In the current numerical study, the atomic behavior of H2O-CuO nanofluid inside Pt microchannel is described using Molecular Dynamics simulation. The results are reported by calculating physical properties such as temperature, total energy, density, velocity, temperature profile, and aggregation time. In our simulations, H2O-CuO nanofluid inside Pt microchannel is represented by Universal Force Field, TIP4P, and Embedded Atom Model. The simulation results show that the total energy of atomic structures converged to −509910 eV value after 10 ns. This calculation estimated the atomic stability of structures. Also, simulations predicted microchannel thickness is an important parameter for nanofluid flow. By increasing microchannel thickness, the absorption force between Pt atoms and nanofluid particles increases. Numerically, by increasing microchannel thickness to 15, the maximum density, velocity, and temperature profiles reach 1.23 g/cm3, 0.0065 Å/ps, and 264 K, respectively. Furthermore, by microchannel thickness increasing from 5 to 15, CuO nanoparticles’ aggregation time and potential energy increase from 1.32 ns and −659328 eV to 2.11 ns and −721583 eV. Physically, because of the amplitude of the atomic displacement, this atomic process occurs and decreases with the enlargement of the atomic layers. The movement atomic of various particles of H2O/CuO nanofluid increases by microchannel walls thickening and nanoparticles aggregation phenomenon occur in higher time.

The Molecular Dynamics study of atomic structure behavior of LL-37 peptide as the antimicrobial agent, derived from the human cathelicidin, inside a nano domain filled by the aqueous environment

The LL-37 peptide is an antimicrobial agent derived from human cathelicidin. In addition to their antimicrobial properties, these peptides can activate the immune system through various mechanisms and contribute to autoimmune diseases. In the current study, we describe the atomic behavior of this protein in an aqueous environment inside of metallic nanochannel (Fe nanochannel). For this purpose, Molecular Dynamics (MD) approach was implemented in equilibrium conditions. A Large Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is used in this computational study. Computationally, the various atoms interaction described by Universal Force Field (UFF), TIP4P, and Embedded Atom Model (EAM). Furthermore, physical factors like potential energy, temperature, Radial Distribution Function (RDF), density/velocity/temperature profiles, and protein volume were calculated for atomic behavior description of the LL-37 protein-water system. MD outputs indicated the atomic stability of protein structure in an aqueous environment inside metallic nanochannels. Numerically, the LL-37 protein volume changes from 3906.81 Å3 to 3900.11 Å3 value after t = 10 ns. Also, the maximum density and velocity/temperature profiles reach 0.0225 atoms/Å3 and 0.0124 Å/fs/435.22 K (respectively), values detected in the initial/final and middle bins MD box.

Atomistic simulation of α-Fe(100)-lead-bismuth eutectic (LBE) solid-liquid interface

Behaviors of body centered cubic (bcc) Fe(100)-liquid lead-bismuth eutectic (LBE) solid-liquid interface have been studied by classical molecular dynamics simulation (MD) with embedded-atom model potential under anaerobic conditions. Both static and dynamic simulation results indicate that Fe atoms prefer to bind with Bi atoms rather than Pb atoms. Trajectories of Bi and Pb perpendicular to the interface show obvious thermal vibrations of both liquid components at the time scale of about 0.9 ns for atoms Bi, and about 0.3 ns for atoms Pb, respectively. Temperature effect on penetration of liquid atoms into bulk Fe and dissolution of Fe into liquid in the solid-liquid interface system show that interactions between the bcc Fe(100) and liquid LBE mount perceptibly in the temperature range of 823 to 873 K. This result indicates that the critical temperature of the interaction between the bcc Fe(100) and liquid LBE is between 823 K and 873 K, which is consistent with the designed operating temperature for LBE coolant.

Development of data-driven spd tight-binding models of Fe—parameterisation based on QSGW and DFT calculations including information about higher-order elastic constants

Quantum-mechanical (QM) simulations, thanks to their predictive power, can provide significant insights into the nature and dynamics of defects such as vacancies, dislocations and grain boundaries. These considerations are essential in the context of the development of reliable, inexpensive and environmentally friendly alloys. However, despite significant progress in computer performance, QM simulations of defects are still extremely time-consuming with ab-initio/non-parametric methods. The two-centre Slater–Koster (SK) tight-binding (TB) models can achieve significant computational efficiency and provide an interpretable picture of the electronic structure. In some cases, this makes TB a compelling alternative to models based on abstraction of the electronic structure, such as the embedded atom model. The biggest challenge in the implementation of the SK method is the estimation of the optimal and transferable parameters that are used to construct the Hamiltonian matrix. In this paper, we will present results of the development of a data-driven framework, following the classical approach of adjusting parameters in order to recreate properties that can be measured or estimated using ab-initio or non-parametric methods. Distinct features include incorporation of data from QSGW (quasi-particle self-consistent GW approximation) calculations, as well as consideration of higher-order elastic constants. Furthermore, we provide a description of the optimisation procedure, omitted in many publications, including the design stage. We also apply modern optimisation techniques that allow us to minimise constraints on the parameter space. In summary, this paper introduces some methodological improvements to the semi-empirical approach while addressing associated challenges and advantages.

Free energies of iron phases at high pressure and temperature: Molecular dynamics study

The crystal structure of iron, the major component of the Earth's inner core (IC), is unknown under the IC high pressure (P) (3.3--3.6 Mbar) and temperature (T) (5000--7000 K). Experimental and theoretical data on the phase diagram of iron at these extreme PT conditions are contradictory. Applying quasi-ab initio and ab initio molecular dynamics we computed free energies of the body-centered cubic (bcc), hexagonal close-packed (hcp), and liquid phases. The ionic free energies, computed for the embedded-atom model, were corrected for electronic entropy. Such correction brings the melting temperatures of the hcp iron in very good agreement with previous ab initio data. This validates the calculation of the bcc phase, where fully ab initio treatment is not technically possible due to large sizes required for convergence. The resulting phase diagram shows stabilization of the bcc phase prior to melting in the pressure range of the IC. The melting temperature of the bcc phase is equal to 7190 K at the pressure 360 GPa.

Molecular dynamics study of the mechanical properties of reinforced silicon structure with iron nanoparticles

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.

Lattice ground states for embedded-atom models in 2D and 3D

The Embedded-Atom Model (EAM) provides a phenomenological description of atomic arrangements in metallic systems. It consists of a configurational energy depending on atomic positions and featuring the interplay of two-body atomic interactions and nonlocal effects due to the corresponding electronic clouds. The purpose of this paper is to mathematically investigate the minimization of the EAM energy among lattices in two and three dimensions. We present a suite of analytical and numerical results under different reference choices for the underlying interaction potentials. In particular, Gaussian, inverse-power, and Lennard-Jones-type interactions are addressed.

Calculation of elastic constants of embedded-atom-model potentials in the NVT ensemble

A method for the calculation of elastic constants in the NVT ensamble using molecular dynamics (MD) simulation with a realistic many-body embedded-atom-model (EAM) potential is studied in detail. It is shown that, in such NVT MD simulations, the evaluation of elastic constants is robust and accurate because it gives the elastic tensor in a single simulation which converges using a small number of time steps and particles. These results highlight the applicability of this method in (i) the calculation of local elastic constants of nonhomogeneous crystalline materials and (ii) the calibration of interatomic potentials, as a fast and accurate alternative to the common method of explicit deformation, which requires a set of consistent simulations at different conditions. The method is demonstrated for the calculation of the elastic constants of copper in the temperature range of 0-1000K, and results agree with the target values used for the potential calibration. The various contributions to the values of the elastic constants, namely, the Born, stress fluctuation, and ideal gas terms, are studied as a function of temperature.