Showing papers on "Interatomic potential published in 2008"
TL;DR: In this article, the interaction of C atoms with a screw and an edge dislocation is modelled at an atomic scale using an empirical Fe-C interatomic potential based on the embedded atom method and molecular statics simulations.
171 citations
TL;DR: In this paper, a molecular dynamics approach for determination of the internal relaxation displacement in a single-layer graphene sheet under macroscopically homogeneous in-plane deformation was developed.
Abstract: For noncentrosymmetric crystals, internal lattice relaxation must be considered for theoretical predictions of elastic properties. This paper develops a molecular dynamics approach for determination of the internal relaxation displacement in a single-layer graphene sheet under macroscopically homogeneous in-plane deformation. Based on an analytical interatomic potential, a generally nonlinear relationship between the internal relaxation displacement and the applied macroscopic strain is obtained explicitly from molecular dynamics simulations with a rhombic unit cell under finite deformation. A linear relationship is derived for relatively small strains, which can be conveniently incorporated into a continuum description of the elastic behavior of graphene. It is found that the internal relaxation has a strong effect on theoretical elastic moduli of graphene. In addition, the relationship between elastic properties for graphene and carbon nanotubes is discussed.
169 citations
TL;DR: In this paper, a neon-neon interatomic potential energy curve was derived from quantum-mechanical ab initio calculations using basis sets of up to t-aug-cc-pV6Z quality supplemented with bond functions and AB initio methods up to CCSDT(Q).
Abstract: A neon–neon interatomic potential energy curve was derived from quantum-mechanical ab initio calculations using basis sets of up to t-aug-cc-pV6Z quality supplemented with bond functions and ab initio methods up to CCSDT(Q). In addition, corrections for relativistic effects were determined. An analytical potential function was fitted to the ab initio values and utilised to calculate the rovibrational spectra. The quality of the interatomic potential function was tested by comparison of the calculated spectra with experimental ones and those derived from other potentials of the literature. In a following paper the new interatomic potential is applied in the framework of the quantum-statistical mechanics and of the corresponding kinetic theory to determine selected thermophysical properties of neon governed by two-body and three-body interactions.
147 citations
TL;DR: Jager et al. as discussed by the authors proposed an argon-argon interatomic potential energy curve determined from quantum-mechanical ab initio calculations and described with an analytical representation, which was used to calculate the most important thermophysical properties of argon governed by two-body interactions.
Abstract: A recent argon–argon interatomic potential energy curve determined from quantum-mechanical ab initio calculations and described with an analytical representation [B. Jager, R. Hellmann, E. Bich, and E. Vogel, Mol. Phys. 107, 2181 (2009); 108, 105 (2010)] was used to calculate the most important thermophysical properties of argon governed by two-body interactions. Second pressure, acoustic, and dielectric virial coefficients as well as viscosity and thermal conductivity in the limit of zero density were computed for natural argon from 83 to 10,000 K. The calculated values for the different thermophysical properties are compared with available experimental data and values computed for other argon–argon potentials. This extensive analysis shows that the proposed potential is superior to all previous ones and that the calculated thermophysical property values are accurate enough to be applied as standard values for the complete temperature range of the calculations.
139 citations
TL;DR: In this paper, an empirical potential based on insights from density functional theory was proposed to describe short-ranged covalent bonding of the carbon $p$ electrons, and the potential correctly describes the interaction of carbon and iron across a wide range of defect environments.
Abstract: Existing interatomic potentials for the iron-carbon system suffer from qualitative flaws in describing even the simplest of defects. In contrast to more accurate first-principles calculations, all previous potentials show strong bonding of carbon to overcoordinated defects (e.g., self-interstitials, dislocation cores) and a failure to accurately reproduce the energetics of carbon-vacancy complexes. Thus any results from their application in molecular dynamics to more complex environments are unreliable. The problem arises from a fundamental error in potential design---the failure to describe short-ranged covalent bonding of the carbon $p$ electrons. We describe a resolution to the problem and present an empirical potential based on insights from density-functional theory, showing covalent-type bonding for carbon. The potential correctly describes the interaction of carbon and iron across a wide range of defect environments. It has the embedded atom method form and hence appropriate for billion atom molecular-dynamics simulations.
134 citations
TL;DR: In this article, a finite deformation shell theory for single-wall carbon nanotubes based on the interatomic potential was developed for CNTs, which incorporates the effect of bending moment and curvature for a curved surface, and accurately accounts for the nonlinear, multi-body atomistic interactions as well as the CNT chirality.
Abstract: A finite-deformation shell theory is developed for single-wall carbon nanotubes (CNTs) based on the interatomic potential. The modified Born rule for Bravais multi-lattice is used to link the continuum strain energy density to the interatomic potential. The theory incorporates the effect of bending moment and curvature for a curved surface, and accurately accounts for the nonlinear, multi-body atomistic interactions as well as the CNT chirality. It avoids the amibiguous definition of nanotube thickness, and provides the constitutive relations among stress, moment, strain and curvature in terms of the interatomic potential.
132 citations
TL;DR: It is shown that the average interatomic distances of the nanoparticles are most significantly affected by the creation of oxygen vacancies, and the stability of octahedral ceria particles at small sizes is supported by interatomic potential-based global optimisations probing the low energy isomers of the Ce19O32 nanoparticle.
Abstract: Density functional plane-wave calculations have been performed to investigate a series of ceria nanoparticles (CeO2−x)n, n ≤ 85. Strong correlation effects of the Ce f-electron introduced upon Ce4+ → Ce3+ reduction have been accounted for through the use of an effective on-site Coulomb repulsive interaction within the so-called DFT+U approach. Twelve nanoparticles of up to 2 nm in diameter and of both cuboctahedral and octahedral forms are chosen as representative model systems. Energetic and structural effects of oxygen vacancy formation in these nanoparticles are discussed with respect to those in the bulk and on extended surfaces. We show that the average interatomic distances of the nanoparticles are most significantly affected by the creation of oxygen vacancies. The formation energies of non-stoichiometric nanoparticles (CeO2−x)n are found to scale linearly with the average coordination number of Ce atoms; where x < 0 species, containing partially reduced O atoms, are less stable. The stability of octahedral ceria particles at small sizes, and the predicted strong propensity of Ce cations to acquire a reduced state at lower coordinated sites, is supported by interatomic potential-based global optimisations probing the low energy isomers of the Ce19O32 nanoparticle.
122 citations
TL;DR: In this paper, the modified embedded-atom method (MEAM) interatomic potentials for the Fe-Ti-C and Fe -Ti-N ternary systems have been developed based on the previously developed MEAM potentials.
121 citations
TL;DR: In this article, the authors describe theoretical and computational studies associated with the interface elastic properties of noncoherent metallic bicrystals and derive analytical forms of interface energy, interface stresses, and interface elastic constants in terms of interatomic potential functions.
Abstract: The paper describes theoretical and computational studies associated with the interface elastic properties of noncoherent metallic bicrystals. Analytical forms of interface energy, interface stresses, and interface elastic constants are derived in terms of interatomic potential functions. Embedded-atom method potentials are then incorporated into the model to compute these excess thermodynamics variables, using energy minimization in a parallel computing environment. The proposed model is validated by calculating surface thermodynamic variables and comparing them with preexisting data. Next, the interface elastic properties of several fcc-fcc bicrystals are computed. The excess energies and stresses of interfaces are smaller than those on free surfaces of the same crystal orientations. In addition, no negative values of interface stresses are observed. Current results can be applied to various heterogeneous materials where interfaces assume a prominent role in the systems' mechanical behavior.
112 citations
TL;DR: In this article, a discussion concerning the concept, method and detailed construction procedure of seven interatomic potentials currently available for fcc, bcc and hcp transition metals and their binary alloys is presented.
111 citations
TL;DR: In this article, the authors developed an equilibrium and non-equilibrium extension of the quasicontinuum (QC) method by coupling the local temperature-dependent free energy furnished by the maxent approximation scheme to the heat equation in a joint thermo-mechanical variational setting.
Abstract: The aim of this paper is the development of equilibrium and non-equilibrium extensions of the quasicontinuum (QC) method. We first use variational mean-field theory and the maximum-entropy (max-ent) formalism for deriving approximate probability distribution and partition functions for the system. The resulting probability distribution depends locally on atomic temperatures defined for every atom and the corresponding thermodynamic potentials are explicit and local in nature. The method requires an interatomic potential as the sole empirical input. Numerical validation is performed by simulating thermal equilibrium properties of selected materials using the Lennard–Jones (LJ) pair potential and the embedded-atom method (EAM) potential and comparing with molecular dynamics results as well as experimental data. The max-ent variational approach is then taken as a basis for developing a three-dimensional non-equilibrium finite-temperature extension of the QC method. This extension is accomplished by coupling the local temperature-dependent free energy furnished by the max-ent approximation scheme to the heat equation in a joint thermo-mechanical variational setting. Results for finite-temperature nanoindentation tests demonstrate the ability of the method to capture non-equilibrium transport properties and differentiate between slow and fast indentation.
TL;DR: Ackland et al. as mentioned in this paper investigated the effect of the dislocation segment in the 70°-mixed orientation with the interatomic potential on the critical line shape at which the dislocations breaks from the void and found that the effect on the line shape does not arise from anisotropy of the elastic line tension.
Abstract: Atomic processes and strengthening effects due to interaction between edge dislocations and voids in α-iron have been investigated by means of molecular dynamics with a recently developed interatomic potential (Ackland et al 2004 J. Phys.: Condens. Matter 16 S2629) and compared with those obtained earlier with an older potential (Ackland et al 1997 Phil. Mag. A 75 713). Differences between the interactions for the two models are insignificant at temperature T≥100 K, thereby confirming the validity of the previous results. In particular, voids are relatively strong obstacles because for large voids and/or low temperature, the initially straight edge dislocation is pulled into screw orientation before it breaks away at the critical shear stress, τc. Differences between the core structures and glide planes of the screw dislocation for the two potentials do not affect τc in this temperature range. The only significant difference between the dislocation–void interactions in the two models occurs at low temperature in static or pseudo-static conditions (T≤1 K). It arises from the influence of the dislocation segment in the 70°-mixed orientation with the (Ackland et al 2004 J. Phys.: Condens. Matter 16 S2629) potential and is seen in the critical line shape at which the dislocation breaks from the void. It affects τc for some combinations of void size and spacing. The effect on the line shape does not arise from anisotropy of the elastic line tension: it is due to the high Peierls stress of the 70° dislocation. When this effect does not control breakaway, the dependence of τc on void size and spacing follows an equation first found by modelling the Orowan process in the approximation of linear elasticity.
TL;DR: In this paper, an atomistic-based finite-deformation shell theory was proposed to approximate SWCNTs as thin shells, which avoids the shell thickness and Young's modulus, but links the tension and bending rigidities directly to the interatomic potential.
Abstract: Single-wall carbon nanotubes (SWCNT) have been frequently modeled as thin shells, but the shell thickness and Young's modulus reported in literatures display large scattering. The order of error to approximate SWCNTs as thin shells is studied in this paper via an atomistic-based finite-deformation shell theory, which avoids the shell thickness and Young's modulus, but links the tension and bending rigidities directly to the interatomic potential. The ratio of atomic spacing ( Δ ≈0.14 nm) to the radius of SWCNT, Δ / R , which ranges from zero (for graphene) to 40% [for a small (5,5) armchair SWCNT ( R =0.35 nm)], is used to estimate the order of error. For the order of error O [( Δ / R ) 3 ], SWCNTs cannot be represented by a conventional thin shell because their constitutive relation involves the coupling between tension and curvature and between bending and strain. For the order of error O [( Δ / R ) 2 ], the tension and bending (shear and torsion) rigidities of SWCNTs can be represented by an elastic orthotropic thin shell, but the thickness and elastic modulus cannot. Only for the order of error O ( Δ / R ), a universal constant shell thickness can be defined and SWCNTs can be modeled as an elastic isotropic thin shell.
TL;DR: In this article, the mesoscopic vacancy dislocation loops observed in ion-irradiated materials are, without exception, metastable with respect to the transformation into spherical voids, but the rate of this transformation and even the specific type of the transformation mechanism depend on the defect size and the properties of the material.
Abstract: The most recent observations of dynamical time-dependent fluctuating behaviour of mesoscopic radiation defects in body-centred cubic metals (Arakawa et al 2006 Phys. Rev. Lett. 96 125506; 2007 Science 318 956–9; Yao et al 2008 Phil. Mag. at press) have highlighted the need to develop adequate quantitative models for the structural stability of defects in the mesoscopic limit where defects are accessible to direct in situ electron microscope imaging. In pursuit of this objective, we investigate and compare several types of mesoscopic vacancy and interstitial defects in iron and tungsten by simulating them using recently developed many-body interatomic potentials. We show that the mesoscopic vacancy dislocation loops observed in ion-irradiated materials are, without exception, metastable with respect to the transformation into spherical voids, but that the rate of this transformation and even the specific type of the transformation mechanism depend on the defect size and the properties of the material.
TL;DR: A semi-empirical interatomic potential for carbon has been developed, based on the modified embedded atom method formalism, which describes the structural properties of various polytypes of carbon, elastic, defect and surface properties of diamonds as satisfactorily as the well-known Tersoff potential as discussed by the authors.
Abstract: A semi-empirical interatomic potential for carbon has been developed, based on the modified embedded atom method formalism. The potential describes the structural properties of various polytypes of carbon, elastic, defect and surface properties of diamonds as satisfactorily as the well-known Tersoff potential. Combined with the Lennard-Jones potential, it can also reproduce the physical properties of graphite and amorphous carbon reasonably well. The applicability of the present potential to atomistic approaches on carbon nanotubes and fullerenes is also shown. The potential has the same formalism as previously developed MEAM potentials for bcc, fcc and hcp elements, and can be easily extended to describe various metal–carbon alloy systems.
TL;DR: In this article, the authors studied the indentation response of Ni thin films of thicknesses in the nanoscale using molecular dynamics simulations with embedded atom method (EAM) interatomic potentials.
TL;DR: In this paper, an existing palladium embedded-atom method potential was extended to construct a new Pd-H embedded atom method potential by normalizing the elemental embedding energy and electron density functions.
Abstract: Palladium hydrides have important applications. However, the complex Pd–H alloy system presents a formidable challenge to developing accurate computational models. In particular, the separation of a Pd–H system to dilute (α) and concentrated (β) phases is a central phenomenon, but the capability of interatomic potentials to display this phase miscibility gap has been lacking. We have extended an existing palladium embedded-atom method potential to construct a new Pd–H embedded-atom method potential by normalizing the elemental embedding energy and electron density functions. The developed Pd–H potential reasonably well predicts the lattice constants, cohesive energies, and elastic constants for palladium, hydrogen, and PdHx phases with a variety of compositions. It ensures the correct hydrogen interstitial sites within the hydrides and predicts the phase miscibility gap. Preliminary molecular dynamics simulations using this potential show the correct phase stability, hydrogen diffusion mechanism, and mechanical response of the Pd–H system.
TL;DR: An analytic approach is established to determine the tensile and bending stiffness of a hexagonal boron-nitride (h-BN) monolayer and single- and multi-wall boronsnitride nanotubes (BNNTs) directly from the interatomic potential.
Abstract: We establish an analytic approach to determine the tensile and bending stiffness of a hexagonal boron-nitride (h-BN) monolayer and single- and multi-wall boron-nitride nanotubes (BNNTs) directly from the interatomic potential. Such an approach enables one to bypass atomistic simulations and to give the tensile and bending stiffness in terms of the parameters in the potential. For single- and multi-wall BNNTs, the stiffness also depends on the (inner most or outer most) wall radius and the number of the walls. The thickness of h-BN monolayer is also discussed.
TL;DR: In this article, a surface Cauchy-Born approach is proposed to model non-centrosymmetric, semiconducting nanostructures such as silicon that exist in a diamond cubic lattice structure.
TL;DR: In this article, the effect of adding a Hubbard Ueff term to the gradient-corrected (GGA) functional is investigated, but whereas good agreement is shown with experimental data when pure GGA (Ueff = 0) is employed, for values of Ueff greater than zero the solution becomes unphysical, indicating that the Fe valence electrons within mackinawite are delocalized.
Abstract: The iron sulfide mackinawite (FeS) is modeled by density functional theory calculations, the results of which are used to derive a set of interatomic potentials for this material. We have investigated the effect of adding a Hubbard Ueff term to the gradient-corrected (GGA) functional, but whereas good agreement is shown with experimental data when pure GGA (Ueff = 0) is employed, for values of Ueff greater than zero the solution becomes unphysical, an indication that the Fe valence electrons within mackinawite are delocalized. This property is further evidenced by the density of states, which confirms a metallic nature from delocalization of the Fe d orbital at all Ueff values. Mackinawite is calculated to be a nonmagnetic material, in accord with experiment. We have also derived a set of interatomic potentials by fitting to observables including geometry, phonon frequencies, and elastic constants, which were calculated for isolated mackinawite layers using DFT. The derived potential model is used to calc...
TL;DR: In this paper, an electron-temperature-dependent empirical interatomic potential for tungsten has been developed, which can be used to model such phenomena using classical molecular dynamics simulations.
Abstract: Irradiation of a metal by lasers or swift heavy ions causes the electrons to become excited. In the vicinity of the excitation, an electronic temperature is established within a thermalization time of 10-100 fs, as a result of electron-electron collisions. For short times, corresponding to less than 1 ps after excitation, the resulting electronic temperature may be orders of magnitude higher than the lattice temperature. During this short time, atoms in the metal experience modified interatomic forces as a result of the excited electrons. These forces can lead to ultrafast nonthermal phenomena such as melting, ablation, laser-induced phase transitions, and modified vibrational properties. We develop an electron-temperature-dependent empirical interatomic potential for tungsten that can be used to model such phenomena using classical molecular dynamics simulations. Finite-temperature density functional theory calculations at high electronic temperatures are used to parametrize the model potential.
TL;DR: In this paper, an interatomic potential for gold, based on the ReaxFF framework, is presented and compared to existing gold potentials available in the literature, which is an attractive basis for extending to the complete AuSCH-system.
Abstract: Atomistic simulations of the chemistry of thiol-gold-systems have been restricted by the lack of interatomic interaction models for the involved elements. The ReaxFF framework already has potentials for hydrocarbons, making it an attractive basis for extending to the complete AuSCH-system. Here, an interatomic potential for gold, based on the ReaxFF framework, is presented and compared to existing gold potentials available in the literature.
TL;DR: In this article, high pressure angle dispersive x-ray diffraction measurements are carried out on LuVO4 in a diamond anvil cell up to 33 GPa at the Elettra synchrotron radiation source.
Abstract: High pressure angle dispersive x-ray diffraction measurements are carried out on LuVO4 in a diamond anvil cell up to 33 GPa at the Elettra synchrotron radiation source. The measurements show that LuVO4 undergoes a zircon to scheelite structure phase transition with a volume change of about 11% at about 8 GPa. A second transition to a monoclinic fergusonite structure occurs above 16 GPa. The data are also recorded while releasing the pressure, and indicate that the scheelite phase is metastable under ambient conditions. The equations of state and changes in internal structural parameters are reported for various phases of LuVO4. Lattice dynamical calculations based on a transferable interatomic potential were also performed and the results support the stability of the scheelite structure at high pressures. The calculated structure, equation of state and bulk modulus for all the phases are in fair agreement with the experimental observations.
TL;DR: In this paper, the authors used the quasicontinuum method to examine the mechanical behavior and underlying mechanisms of surface plasticity in nanocrystalline aluminum with a grain diameter of 7nm deformed under wedge-like cylindrical contact.
TL;DR: In this paper, the potentials of UO 2 fuel are investigated on their applicability to model structural stabilities beyond fluorite phase by comparing with ab initio results, and a high pressure cotunnite phase and loosely stacking virtual crystal are involved in order to get a primary confidence for large-scale deformation modelings of uO 2 under irradiation damages.
TL;DR: In this article, the melting points and other thermal properties of several semiconducting and metallic elements are modeled by different empirical interatomic potential models, including the Stillinger-Weber, the embedded-atom method, the Finnis-Sinclair and the modified-embedded-atom methods.
Abstract: We report melting points and other thermal properties of several semiconducting and metallic elements as they are modeled by different empirical interatomic potential models, including the Stillinger–Weber, the embedded-atom method, the Finnis–Sinclair and the modified-embedded-atom method. The state-of-the-art free energy methods are used to determine the melting points of these models within a very small error bar, so that they can be cross-compared with each other. The comparison reveals several systematic trends among elements with the same crystal structure. It identifies areas that require caution in the application of these models and suggests directions for their future improvement.
TL;DR: In this paper, an efficient interatomic potential for PbTiO3 in the framework of the shell model was developed by fitting its parameters to reproduce both the mechanical and ferroelectric properties derived from ab initio density functional theory calculations.
Abstract: We have developed an efficient interatomic potential for PbTiO3 in the framework of the shell model by fitting its parameters to reproduce both the mechanical and ferroelectric properties derived from ab initio density functional theory calculations The optimized potential successfully yields the crystal structures, elastic properties and phonon dispersion curves, whereas the spontaneous polarization and effective charges are slightly underestimated It reproduces well characteristic ferroelectric (FE) and antiferrodistortive (AFD) instabilities closely associated with the structural phase transition in PbTiO3, and is reliable under high tension and compression along the [001] direction Furthermore, the potential is effective enough to describe 180? and 90? domain walls as well as the PbO-terminated surface with c(2 ? 2) reconstruction where the FE and AFD distortions coexist This significant success widely extends the applicable range of atomic-level simulations of ferroelectrics based on the shell model potential
TL;DR: In this paper, an interatomic potential for ruthenium based on the embedded atom method framework with the Finnis/Sinclair representation was developed and validated for a stable hcp lattice with reasonable lattice and elastic constants and surface and stacking fault energies.
Abstract: We develop and validate an interatomic potential for ruthenium based on the embedded atom method framework with the Finnis/Sinclair representation. We confirm that the potential yields a stable hcp lattice with reasonable lattice and elastic constants and surface and stacking fault energies. We employ molecular dynamics simulations to bring two surfaces together, one flat and the other with a single asperity. We compare the process of asperity contact formation and breaking in Au and Ru, two materials currently in use in microelectromechanical system switches. While Au is very ductile at 150 and 300 K, Ru shows considerably less plasticity at 300 and 600 K (approximately the same homologous temperature). In Au, the asperity necks down to a single atom thick bridge at separation. While similar necking occurs in Ru at 600 K, it is much more limited than in Au. On the other hand, at 300 K, Ru breaks by a much more brittle process of fracture/decohesion with limited plastic deformation.
TL;DR: A modified embedded-atom method (MEAM) interatomic potential for the Cu-Zr system has been developed based on the previously developed MEAM potentials for pure Cu and Zr as mentioned in this paper.
Abstract: A modified embedded-atom method (MEAM) interatomic potential for the Cu–Zr system has been developed based on the previously developed MEAM potentials for pure Cu and Zr. The potential describes fundamental physical properties and alloy behavior of the Cu–Zr binary system reasonably well. The applicability of the potential to atomistic investigations of mechanical and deformation behavior for the Cu–Zr binary and Cu–Zr-based multicomponent amorphous alloys is also demonstrated by showing that fully relaxed and realistic amorphous structures can be generated by molecular dynamics simulations.
TL;DR: In this paper, an angle-dependent interatomic potential has been developed for the Cu-Ta system by crossing two existing potentials for pure Cu and Ta, and the cross-interaction functions have been fitted to first-principles data generated in this work.
Abstract: An angle-dependent interatomic potential has been developed for the Cu-Ta system by crossing two existing potentials for pure Cu and Ta. The cross-interaction functions have been fitted to first-principles data generated in this work. The potential has been extensively tested against first-principles energies not included in the fitting database and applied to molecular dynamics simulations of wetting and dewetting of Cu on Ta. We find that a Cu film placed on a Ta (110) surface dewets from it, forming a Cu droplet on top of a stable Cu monolayer. We also observe that a drop of liquid Cu placed on a clean Ta (110) surface spreads over it as a stable monolayer, while the extra Cu atoms remain in the drop. The stability of a Cu monolayer and instability of thicker Cu films are consistent with recent experiments and first-principles calculations. This agreement demonstrates the utility of the potential for atomistic simulations of Cu-Ta interfaces.