Effects of Angular Dependent Terms in the Interatomic Potential on Defect Properties in TiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
Julia Panova ◽  
Diana Farkas
Keyword(s):  
Interatomic Potential ◽  
Stacking Faults ◽  
Core Structure ◽  
Interatomic Potentials ◽  
The Core ◽  
Embedded Atom ◽  
Dependent Term

AbstractInteratomic potentials of the Embedded Atom and Embedded Defect types were used to study the effect of the angular dependent term in the Embedded Defect potential on the properties of defects in TiAl. The defect properties were computed with interatomic potentials developed with and without angular dependent terms. It was found that the inclusion of the angular dependent terms tends to increase the energies of the APB’s and lower the energies of stacking faults. The effects of the angular term on the relaxation around vacancies and antisites in TiAl was also studied, as well as the core structure of several dislocations in this compound.

Atomistic Simulation of Dislocation Motion as Determined by Core Structure

1994 ◽  
Vol 350 ◽  
Author(s):  
Kevin Ternes ◽  
Diana Farkas ◽  
Zhao-Yang Xie
Keyword(s):  
Atomistic Simulation ◽  
Dislocation Core ◽  
Dislocation Motion ◽  
Core Structure ◽  
Planar Structure ◽  
Interatomic Potentials ◽  
Atom Type ◽  
The Core ◽  
Embedded Atom ◽  
Structure And Motion

AbstractTwo different interatomic potentials of the embedded atom type were used to study the relationships between dislocation core structure and mobility. Core structures were computed for a variety of dislocations in B2 NiAl. Several non-planar cores were studied as they reacted to applied stress and moved. The results show that in some cases, the dislocation core transforms to a planar structure before the dislocation glides, whereas in some other cases the core retains the non-planar structure at stresses sufficient to sustain glide. The effects of stoichiometry deviations on the core structure and motion were also studied.

Computer Simulation Study of the Effects of Copper Precipitates on Dislocation Core Structure in Ferritic Steels

1996 ◽  
Vol 439 ◽  
Author(s):  
T. Harry ◽  
D. J. Bacon
Keyword(s):  
Dislocation Core ◽  
Alloy System ◽  
Lattice Parameter ◽  
Transformation Process ◽  
Core Structure ◽  
Metastable Equilibrium ◽  
Precipitate Size ◽  
Ferritic Steels ◽  
Interatomic Potentials ◽  
The Core

AbstractThe small, coherent BCC precipitates of copper that form during fast neutron irradiation of ferritic steels are an important component of in-service irradiation hardening. Many-body interatomic potentials for the Fe-Cu alloy system have been developed and used to simulate the atomic structure of the ½<111> screw dislocation in both pure a-iron and the metastable BCC phase of copper. In iron, the core has the well-known 3-fold form of atomic disregistry. In BCC copper, however, the core structure depends on the lattice parameter. At the metastable equilibrium value, the core is similar to that in iron, but as the lattice parameter is reduced, as in a precipitate, the core becomes delocalised by transformation of the copper. Simulation of dislocated crystals containing precipitates shows that the extent of this effect depends on precipitate size. The energy changes indicate a significant dislocation pinning effect due to this dislocation-induced precipitate transformation process.

Modeling of supersonic crowdion clusters in FCC lattice: Effect of the interatomic potential

2021 ◽  
pp. 2050019
Author(s):  
Igor A. Shelepev ◽  
Ayrat M. Bayazitov ◽  
Elena A. Korznikova
Keyword(s):  
Interatomic Potential ◽  
High Energy ◽  
Propagation Path ◽  
Interatomic Potentials ◽  
Energy Localization ◽  
Many Body ◽  
Embedded Atom ◽  
Fcc Lattice ◽  
The Many ◽  
Body Potential

Among a wide variety of point defects, crowdions can be distinguished by their high energy of formation and relatively low migration barriers, which makes them an important agent of mass transfer in lattices subjected to severe plastic deformation, irradiation, etc. It was previously shown that complexes and clusters of crowdions are even more mobile than single interstitials, which opened new mechanisms for the transfer of energy and mass in materials under intense external impacts. One of the most popular and convenient methods for analyzing crowdions is molecular dynamics, where the results can strongly depend on the interatomic potential used in the study. In this work, we compare the characteristics of a crowdion in an fcc lattice obtained using two different interatomic potentials — the pairwise Morse potential and the many-body potential for Al developed by the embedded atom method. It was found that the use of the many-body potential significantly affects the dynamics of crowdion propagation, including the features of atomic collisions, the evolution of energy localization and the propagation path.

Empirical Interatomic Potentials for L1O Tial and B2 Nial

1990 ◽  
Vol 213 ◽  
Author(s):  
Satish I. Rao ◽  
C. Woodward ◽  
T.A. Parthasarathy
Keyword(s):  
Interatomic Potential ◽  
Dislocation Core ◽  
Interatomic Potentials ◽  
Electronic Effects ◽  
Bulk Properties ◽  
Embedded Atom ◽  
Fitting Procedure ◽  
Planar Fault ◽  
Potential Methods ◽  
Semi Empirical

ABSTRACTRecent studies have suggested a particular relationship between the degree of covalent bonding in TiAl and the mobility of dislocation[1,2]. Ultimately such electronic effects In ordered compounds must dictate the dislocation core structures and at the same time the dislocation mobility within a given compound. However, direct modelling of line defects Is beyond the capability of todays electronic structure techniques. Alternatively, significant steps toward extending our understanding of the flow behaviour of structural intermetallics may come through general application of empirical interatomic potential methods for calculating the structure and mobility of defects. Toward this end, we have constructed semi-empirical interatomic potentials within the embedded atom formalism for L1O and B2 type structures. These potentials have been determined by fitting to known bulk structural and elastic properties of TIAl and NiAl, using least squares procedures. Simple expressions that relate the parameters of the potentials to the bulk properties are used in the fitting procedure. Calculations of dislocation core structures and planar fault energies using these potentials are considered. The differences between the optimized bulk properties predicted from the potentials and the values for these properties are discussed in terms of non-spherical nature of the electron density distribution. Empirical methods which incorporate these effects into interatomic potentials are briefly discussed.

Beyond the Embedded Atom Interatomic Potential

1988 ◽  
Vol 141 ◽  
Author(s):  
Eduardo J. Savino ◽  
R. Pasianot
Keyword(s):  
Interatomic Potential ◽  
Bond Angle ◽  
Computer Time ◽  
Pair Interaction ◽  
Realistic Model ◽  
Scattering Data ◽  
Interatomic Potentials ◽  
Elastic Neutron ◽  
Embedded Atom ◽  
Defect Simulation

AbstractWe briefly discuss some of the advantages and limitations of using embedded atom interatomic potentials for simulating the static configuration and dynamics of lattice defects. In metals, the embedded atom potentials provide a physically more realistic approximation than simple pair interaction potentials without a significant increase in computer time needed for defect simulation studies. However, in some cases, n-body shear forces, i.e bond angle interatomic forces may be needed for fitting experimental results related to defect configuration. One such example is the elastic neutron scattering data from N interstitials in Nb [1]. Also, such bond angle forces must be included in a realistic model of atomic interactions in metals, expecially in highly anisotropic bee transition metals. Extending the concept of the embedded atom method, we propose a new form for the interatomic potential in metals which includes bond angle forces. General expressions for the elastic constants in bee and fee structures are deduced.

scholarly journals Revealing and Controlling the Core of Screw Dislocations in BCC Metals

2021 ◽  
Author(s):  
Zhaoxuan Wu ◽  
Rui Wang ◽  
Lingyu Zhu ◽  
Subrahmanyam Pattamatta ◽  
David Srolov
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Dislocation Core ◽  
Core Structure ◽  
Valence Electron Concentration ◽  
Interatomic Potentials ◽  
Structure Transition ◽  
The Core ◽  
Bcc Metals ◽  
Dislocation Core Structure

Abstract Body-centred-cubic (BCC) transition metals (TMs) tend to be brittle at low temperatures, posing significant challenges in their processing and major concerns for damage tolerance in critical load-carrying applications. The brittleness is largely dictated by the screw dislocation core structure; the nature and control of which has remained a puzzle for nearly a century. Here, we introduce a universal model and a physics-based material index χ that guides the manipulation of dislocation core structure in all pure BCC metals and alloys. We show that the core structure, commonly classified as degenerate (D) or non-degenerate (ND), is governed by the energy difference between BCC and face-centred cubic (FCC) structures and χ robustly captures this key quantity. For BCC TMs alloys, the core structure transition from ND to D occurs when χ drops below a threshold, as seen in atomistic simulations based on nearly all extant interatomic potentials and density functional theory (DFT) calculations of W-Re/Ta alloys. In binary W-TMs alloys, DFT calculations show that χ is related to the valence electron concentration at low to moderate solute concentrations, and can be controlled via alloying. χ can be quantitatively and efficiently predicted via rapid, low-cost DFT calculations for any BCC metal alloys, providing a robust, easily applied tool for the design of ductile and tough BCC alloys.

Embedded - Atom - Method Interatomic Potentials for BCC - Iron

1992 ◽  
Vol 291 ◽  
Author(s):  
G. Simonelli ◽  
R. Pasianot ◽  
E.J. Savino
Keyword(s):  
Point Defects ◽  
Interatomic Potential ◽  
Lattice Parameter ◽  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Embedded Atom ◽  
Bcc Iron ◽  
Defect Energies ◽  
Functional Fitting ◽  
Formation Energies

ABSTRACTAn embedded-atom-method (EAM) interatomic potential [1] for bcc-iron is derived. It is fitted exactly to the lattice parameter, elastic constants, an approximation to the unrelaxed vacancy formation energy, and Rose's expression for the cohesive energy [2]. Formation energies and relaxation volumes of point defects are calculated. We find that the relative energies of the defect configurations depend on the functional fitting details of the potential considered, mainly its range: the experimental interstitial configuration of lowest energy can be reproduced by changing this parameter. This result is confirmed by calculating the same defect energies using other EAM potentials, based on the ones developed by Harrison et al. [3].

Reliability of EAM potentials for FCC metals properties prediction

2020 ◽  
Author(s):  
◽  
Seyed Moein Rassoulinejad Mousavi
Keyword(s):  
Interatomic Potential ◽  
Elastic Stiffness ◽  
Dynamics Simulation ◽  
Interatomic Potentials ◽  
Validity Of Results ◽  
University Of Missouri ◽  
Embedded Atom ◽  
Different Temperatures ◽  
Experimental Values ◽  
The Right

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI--COLUMBIA AT REQUEST OF AUTHOR.] A perfectly transferable interatomic potential that works for different materials and systems of interest is lacking. This work considers the transferability of several existing interatomic potentials by evaluating their capability at various temperatures, to determine the range of accuracy of these potentials in atomistic simulations. A series of embedded-atom-method (EAM) based interatomic potentials has been examined for precious and popular metals in nanoscale studies. The potentials have been obtained from various credible and trusted repositories and were compared to tackle the lack of a comparison between several existing models. The interatomic potentials designed for the single elements, binary, trinary and higher order compounds were tested for each species using molecular dynamics simulation. Validity of results arising from each potential was investigated against experimental values at different temperatures from a temperature range around Debye temperature to melting point. The data covers accuracy of all studied potentials for prediction of the single crystals' elastic stiffness constants as well as the bulk, shear and Young's modulus of the polycrystalline specimens. As testing and benchmarking results for users is a necessity before running a new simulation, results of this work increase their assurance and lead them to the right model by a way to easily look up data. Referring to this work also prevents any inaccurate prediction by an atomistic simulation due to use of an inappropriate interatomic potential.

The core structure of extrinsic stacking faults in silicon

1978 ◽  
Vol 32 (8) ◽  
pp. 451-453 ◽  
Author(s):  
O. L. Krivanek ◽  
D. M. Maher
Keyword(s):  
Stacking Faults ◽  
Core Structure ◽  
The Core

Quantifying Parameter Sensitivity and Uncertainty for Interatomic Potential Design: Application to Saturated Hydrocarbons

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Mark A. Tschopp ◽  
B. Chris Rinderspacher ◽  
Sasan Nouranian ◽  
Mike I. Baskes ◽  
Steven R. Gwaltney ◽  
...  
Keyword(s):  
Interatomic Potential ◽  
Fractional Factorial ◽  
Interatomic Potentials ◽  
Latin Hypercube Design ◽  
Training Set ◽  
Saturated Hydrocarbons ◽  
Bond Angles ◽  
Embedded Atom ◽  
The Relationship ◽  
Potential Parameters

The research objective herein is to understand the relationships between the interatomic potential parameters and properties used in the training and validation of potentials, specifically using a recently developed modified embedded-atom method (MEAM) potential for saturated hydrocarbons (C–H system). This potential was parameterized to a training set that included bond distances, bond angles, and atomization energies at 0 K of a series of alkane structures from methane to n-octane. In this work, the parameters of the MEAM potential were explored through a fractional factorial design and a Latin hypercube design to better understand how individual MEAM parameters affected several properties of molecules (energy, bond distances, bond angles, and dihedral angles) and also to quantify the relationship/correlation between various molecules in terms of these properties. The generalized methodology presented shows quantitative approaches that can be used in selecting the appropriate parameters for the interatomic potential, selecting the bounds for these parameters (for constrained optimization), selecting the responses for the training set, selecting the weights for various responses in the objective function, and setting up the single/multi-objective optimization process itself. The significance of the approach applied in this study is not only the application to the C–H system but that the broader framework can also be easily applied to any number of systems to understand the significance of parameters, their relationships to properties, and the subsequent steps for designing interatomic potentials under uncertainty.

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