The Infidence of Defect Concentrations on Migration Energies in AgZn Alloys

1988 ◽  
Vol 128 ◽  
Author(s):  
T. D. Andreadis ◽  
M. Rosen ◽  
J. M. Eridon ◽  
D. J. Rosen
Keyword(s):  
Linear Approximation ◽  
Embedded Atom Method ◽  
Local Defect ◽  
Migration Energy ◽  
New Model ◽  
Impurity Atoms ◽  
Embedded Atom ◽  
Defect Reactions ◽  
Eam Potential ◽  
Formation Energies

ABSTRACTMigration energies in Ag of vacancies, interstitials, Zn impurity atoms, interstitial-iipurity cumplexes, and vacancy-impurity complexes were calculated using Embedded Atom. Method (EAM) potentials in Molecular Statics calculations. A new Zn EAM potential was determined and used in these calculations. The dependence of the migration energies on local defect concentrations was determined in a linear approximation. Binding and formation energies of defects are also presented. A new model for the migration energy appropriate for defect reactions is introduced.

scholarly journals A numerical fitting procedure for the embedded atom method interatomic potential and a bridged finite element-molecular dynamics method for large atomic systems

2021 ◽  
Author(s):  
Karthik Narayan
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Embedded Atom Method ◽  
Discretization Scheme ◽  
Element Discretization ◽  
Atomic Systems ◽  
Embedded Atom ◽  
Fitting Procedure ◽  
Numerical Fitting ◽  
Eam Potential

This thesis presents a powerful numerical fitting procedure for generating Embedded Atom Method (EAM) inter-atomic potentials for pure Face Centred Cubic (FCC) and Body Centred Cubic (BCC) metals. The numerical fitting procedure involves assuming a reasonable parameterized form for a portion of the EAM potential, and then fitting the remaining portion to select thermal and elastic properties of the metal. Molecular Dynamics (MD) simulation is used to effect the fitting procedure. The procedure is used to generate an EAM potential for copper, an FCC metal. This resulting EAM potential is used to conduct MD simulations of perfect copper crystals containing voids of different geometries. Following this, a bridged Finite Element-Molecular Dynamics (FE-MD) method is presented, which can be used to simulate large atomic systems much more efficiently than MD simulation alone. The method implements a novel element discretization scheme proposed by the author that is so general that it can be applied to any system of objects interacting with each other via any potential (simple or complex, EAM or otherwise). This bridged FE-MD method is used to reanalyze the voids in the copper crystal lattice. The resulting virial stress increment patterns are found to agree remarkably with the earlier MD simulation results. Furthermore, the bridged FE-MD method is much quicker than the pure MD simulation. These two facts prove the power and usefulness of the bridged FE-MD method, and validate the proposed element discretization scheme

Point defect study of CuTi and CuTi2

1991 ◽  
Vol 6 (3) ◽  
pp. 473-482 ◽  
Author(s):  
J.R. Shoemaker ◽  
R.T. Lutton ◽  
D. Wesley ◽  
W.R. Wharton ◽  
M.L. Oehrli ◽  
...  
Keyword(s):  
Atomistic Simulation ◽  
Formation Energy ◽  
Antisite Defect ◽  
Two Dimensional ◽  
Migration Energy ◽  
Vacancy Migration ◽  
Embedded Atom ◽  
Antisite Defects ◽  
Formation Energies ◽  
Vacancy Migration Energy

The energies and configurations of interstitials and vacancies in the ordered compounds CuTi and CuTi2 were determined using atomistic simulation with realistic embedded-atom potentials. The formation energy of an antisite pair was found to be 0.385 and 0.460 eV in CuTi and CuTi2, respectively. In both compounds, the creation of a vacancy by the removal of either a Cu or Ti atom resulted in a vacant Cu site, with an adjacent antisite defect in the case of the Ti vacancy. The vacant Cu site in CuTi was found to be very mobile within two adjacent (001) Cu planes, with a migration energy of 0.19 eV, giving rise to two-dimensional migration. The vacancy migration energy across (001) Ti planes, however, was 1.32 eV, which could be lowered to 0.75 or 0.60 eV if one or two Cu antisite defects were initially present in these planes. In CuTi2, the vacancy migration energy of 0.92 eV along the (001) Cu plane was significantly higher than in CuTi. The effective vacancy formation energies were calculated to be 1.09 eV and 0.90 eV in CuTi and CuTi2, respectively. Interstitials created by inserting either a Cu or Ti atom had complicated configurations in which a Cu 〈111〉 split interstitial was surrounded by two or three Ti antisite defects. The interstitial formation energy was estimated to be 1.7 eV in CuTi and 1.9 eV in CuTi2.

Grain Boundary Migration in Nanocrystalline Iron

2007 ◽  
Vol 129 ◽  
pp. 145-150 ◽  
Author(s):  
Tomasz Wejrzanowski ◽  
M. Spychalski ◽  
Roman Pielaszek ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Boundary Migration ◽  
3D Models ◽  
Embedded Atom Method ◽  
Interface Motion ◽  
Embedded Atom ◽  
The Matrix ◽  
Nanocrystalline Iron ◽  
Eam Potential ◽  
The Relationship ◽  
Misorientation Angles

In this study a series of 3D models for curved [100] grain boundaries (GBs) in pure α-iron have been constructed. Each model consisted of a spherical grain, with an initial size of about 9 nm, surrounded by a large single-crystal. Different orientations have been assigned to the grain and the matrix in order to obtain interfaces with misorientation angles in the range of 5-45 degrees in steps of 5 degrees. The molecular dynamics with Embedded Atom Method (EAM) potential have been performed for investigation of the temporal changes in GB migration and grain rotations at temperature of 1000 K. The relationship between GB misorientation and its mobility has been found. It was also discovered that the density of the material decreases with a reduction of GB area. The effect of a triple junction on the interface motion has been also studied by introducing a bi-crystal matrix instead of a singlecrystal one. The results are discussed in terms of grain growth investigations in nanometals.

Cascade Overlap in hcp Zirconium: Defect Accumulation and Microstructure Evolution with Radiation using Molecular Dynamics Simulations

2013 ◽  
Vol 1514 ◽  
pp. 37-42 ◽  
Author(s):  
Prithwish K. Nandi ◽  
Jacob Eapen
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Microstructure Evolution ◽  
Stacking Faults ◽  
Embedded Atom Method ◽  
Shockley Partial Dislocation ◽  
Embedded Atom ◽  
Defect Accumulation ◽  
Dynamics Simulations ◽  
Eam Potential

ABSTRACTMolecular dynamics simulations are performed to investigate the defect accumulation and microstructure evolution in hcp zirconium (Zr) – a material which is widely used as clad for nuclear fuel. Cascades are generated with a 3 keV primary knock-on atom (PKA) using an embedded atom method (EAM) potential with interactions modified for distances shorter than 0.1 Å. With sequential cascade simulations we show the emergence of stacking faults both in the basal and prism planes, and a Shockley partial dislocation on the basal plane.

scholarly journals Fatigue crack growth characteristics of Fe and Ni under cyclic loading using a quasi-continuum method

2018 ◽  
Vol 9 ◽  
pp. 1000-1014 ◽  
Author(s):  
Ren-Zheng Qiu ◽  
Yi-Chen Lin ◽  
Te-Hua Fang
Keyword(s):  
Fatigue Crack ◽  
Cyclic Loading ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Loading Modes ◽  
Eam Potential ◽  
Atomic Stress ◽  
Initial Geometry

A quasi-continuum (QC) method based on the embedded atom method (EAM) potential was employed to investigate the fatigue crack growth and expansion characteristics of single-crystal Fe and Ni under cyclic loading modes I and II. In particular, the crack growth and expansion characteristics of Fe and Ni under cyclic loading were evaluated in terms of atomic stress fields and force–distance curves. The simulation results indicated that under cyclic loading, the initially damaged area of the crack will coalesce again after compression or shear to the initial geometry leading to a strengthening of the material. If no coalescence appears, the crack spreads rapidly and the material breaks. Moreover, under the cyclic loading of shear at any orientation, the slip dislocation observed in the materials considerably affects the release of stress.

Molecular Dynamics Simulation of the Elastic Deformation of Nanometer Diameter Metal Clusters

1994 ◽  
Vol 332 ◽  
Author(s):  
Dilip Y. Paithankar ◽  
Julian Talbot ◽  
Ronald P. Andres
Keyword(s):  
Elastic Deformation ◽  
Bulk Material ◽  
Gold Clusters ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Static Compression ◽  
Deformation Curves ◽  
Octahedral Clusters ◽  
Embedded Atom ◽  
Eam Potential

ABSTRACTIndentation using the AFM is a powerful method for determining elastic properties of small supported clusters. However, a theoretical framework has yet to be developed to interpret such measurements. The elastic deformation of nanometer sized gold clusters are modeled using the Embedded Atom Method (EAM) potential of Foiles et al. [1]. Force versus deformation curves are obtained for a series of truncated octahedral clusters having FCC symmetry (N=38, 201, 586, 1289, 2406). It is found that the MD results both for static compression and for harmonic vibration can be analytically estimated by using an elastic constant for the clusters analogous to the elastic modulus of a bulk material. However MD predictions for static compression are not in agreement with the deformation results of Schaefer et al. [2].

Vacancy diffusion along twist grain boundaries in copper

1991 ◽  
Vol 6 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Miki Nomura ◽  
Sing-Yun Lee ◽  
James B. Adams
Keyword(s):  
Grain Boundaries ◽  
Activation Energies ◽  
Vacancy Formation ◽  
Embedded Atom Method ◽  
Vacancy Diffusion ◽  
High Angle ◽  
Self Diffusion ◽  
Embedded Atom ◽  
And Migration ◽  
Formation Energies

Vacancy diffusion along two different high-angle twist grain boundaries (Σ5 and Σ13) was studied using the Embedded Atom Method (EAM). Vacancy formation energies in all the possible sites were calculated and found to be directly related to the degree of coincidence with the neighboring crystal planes. Optimal migration paths and migration energies were determined and found to be very low. The activation energies for self-diffusion at the boundaries were found to be less than half of the bulk value.

Studies of the structure and the atomic diffusion properties of the Σ = 5 [001] twist GB in B2-type intermetallic compound NiAl

2011 ◽  
Vol 89 (7) ◽  
pp. 745-751 ◽  
Author(s):  
Yan-Ni Wen ◽  
Jian-Min Zhang
Keyword(s):  
Intermetallic Compound ◽  
Dynamics Simulation ◽  
Atomic Diffusion ◽  
Embedded Atom Method ◽  
Vacancy Mechanism ◽  
Embedded Atom ◽  
Formation Energies ◽  
Intermetallic Compound Nial ◽  
Diffusion Behaviors ◽  
Diffusion Properties

The structural properties, the formation energies and the atoms’ diffusion behaviors by vacancy mechanism near the Σ = 5 [001] twist GB of the B2-type intermetallic compound NiAl have been investigated by using the modified analytical embedded-atom method and a molecular dynamics simulation. Both the largest displacement and rippling effect occur at the first layer near the GB. The Ni vacancies at uncoincident sites are most easily formed on the first and second layers of the Ni- and Al-terminations, respectively. Furthermore, the Ni vacancy at an uncoincident site on the second layer of the Al-termination tends to migrate to the coincident Ni site of the first layer of the Ni-termination along a six-step jump path. The Ni vacancies at either the coincident or uncoincident site of the first layer tend to migrate in the first layer and finally return to their original site. Therefore, there is a collective tendency for the Ni vacancies to appear in the GB without local disorder.

Quasicontinuum Analysis of Dislocation Propagation during Nanocontact

2014 ◽  
Vol 941-944 ◽  
pp. 470-478
Author(s):  
Hong Sheng Wang ◽  
Yu Shan Ni ◽  
Huai Bao Lu
Keyword(s):  
Formation Mechanism ◽  
Multiscale Model ◽  
Deformation Twinning ◽  
Embedded Atom Method ◽  
Multiscale Simulations ◽  
Embedded Atom ◽  
Planar Fault ◽  
Sheer Stress ◽  
Subsequent Withdrawal ◽  
Eam Potential

Multiscale simulations using the quasicontinuum (QC) method with the embedded-atom method (EAM) potential are performed to investigate the process of nanocontact including sliding and subsequent withdrawal between Ni tip and Au substrate. The multiscale model reveals that deformation twinning in Au substrate is induced not only by the sheer stress but also by the adhesive stress. Combining with the generalized planar fault energy (GPF) curve of Au, the underlying formation mechanism of deformation twinning is studied in detail. During the withdrawal process, the dislocation degeneration and the vacancy evolution are observed.

A Simple Palladium Hydride Embedded Atom Method Potential for Hydrogen Energy Applications

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Iyad Hijazi ◽  
Yang Zhang ◽  
Robert Fuller
Keyword(s):  
Elevated Temperatures ◽  
Clean Energy ◽  
Md Simulations ◽  
Miscibility Gap ◽  
Embedded Atom Method ◽  
Hydrogen Energy ◽  
Hydrogen Purification ◽  
Palladium Hydride ◽  
Embedded Atom ◽  
Eam Potential

When hydrogen is produced from a biomass or coal gasifier, it is necessary to purify it from syngas streams containing components such as CO, CO2, N2, CH4, and other products. Therefore, a challenge related to hydrogen purification is the development of hydrogen-selective membranes that can operate at elevated temperatures and pressures, provide high fluxes, long operational lifetime, and resistance to poisoning while still maintaining reasonable cost. Palladium-based membranes have been shown to be well suited for these types of high-temperature applications and have been widely utilized for hydrogen separation. Palladium's unique ability to absorb a large quantity of hydrogen can also be applied in various clean energy technologies, like hydrogen fuel cells. In this paper, a fully analytical interatomic embedded atom method (EAM) potential for the Pd-H system has been developed, that is easily extendable to ternary Palladium-based hydride systems, such as Pd-Cu-H and Pd-Ag-H. The new potential has fewer fitting parameters than previously developed EAM Pd-H potentials and is able to accurately predict the cohesive energy, lattice constant, bulk modulus, elastic constants, melting temperature, and the stable Pd-H structures in molecular dynamics (MD) simulations with various hydrogen concentrations. The EAM potential also well predicts the miscibility gap, the segregation of the palladium hydride system into dilute (α), and concentrated (β) phases.

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