Finite-Temperature Properties From a Single Zero-Temperature Energy Minimization

1992 ◽  
Vol 278 ◽  
Author(s):  
J. M. Rickman ◽  
R. Najafabadi ◽  
D. J. Srolovitz
Keyword(s):  
Free Energy ◽  
Free Surface ◽  
Energy Minimization ◽  
Formation Energy ◽  
Excess Free Energy ◽  
Lattice Parameter ◽  
Embedded Atom Method ◽  
Zero Temperature ◽  
Embedded Atom ◽  
Eam Potential

AbstractA method for calculating the thermodynamic properties of both perfect crystals and defects from a single zero-temperature energy minimization is described. The validity of the method is demonstrated by determining the free energy and the lattice parameter of a perfect Au crystal, as modelled by an embedded-atom method (EAM) potential. In addition, we determine the temperature dependence of the vacancy formation energy and the excess free energy of a (100) free surface.

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.

Atomistic Simulations of Dislocation-Interface Interactions in the Cu-Ni Multilayer System

1999 ◽  
Vol 578 ◽  
Author(s):  
Satish I. Rao ◽  
Peter M. Hazzledine
Keyword(s):  
Yield Strength ◽  
Elastic Moduli ◽  
Lattice Parameter ◽  
Stacking Fault ◽  
Chemical Effect ◽  
Atomistic Simulations ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Coherency Strains ◽  
Stacking Fault Energies

AbstractMultilayered Cu-Ni has a peak yield strength four orders of magnitude higher than either Cu or Ni because the multitude of interfaces obstruct glissile dislocations. The barrier strengths of the interfaces may be traced to four mismatches across an interface: modulus, lattice parameter, chemical and slip geometry. This paper describes sample embedded atom method (EAM) simulations of dislocations crossing interfaces, designed to separate the effects of the four mismatches. The results confirm some classical calculations and emphasize the importance of three new effects (i) an interface-chemical effect in which dislocations are trapped by core spreading in the interface, (ii) a coherency-chemical effect caused by coherency strains changing effective stacking fault energies and (iii) a coherency-modulus effect in which coherency strains change elastic moduli (and hence the Koehler stress) significantly.

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

Calculation of Material Properties Using Molecular Dynamics Simulation

2007 ◽  
Author(s):  
Y. H. Park ◽  
J. Tang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Melting Point ◽  
Material Properties ◽  
Morse Potential ◽  
Formation Energy ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Dynamics Method

This paper describes the calculation of material properties of copper (Cu) using the molecular dynamics method. Vacancy formation energy, bulk modulus, surface energy and melting point are calculated using different potentials such as the Morse potential and Embedded Atom Method (EAM). Results obtained from different potentials are discussed and compared with experimental results.

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.

Some Thermodynamic Properties of NiAl Calculated by Molecular Dynamics Simulations

1988 ◽  
Vol 133 ◽  
Author(s):  
P. C. Clapp ◽  
M. J. Rubins ◽  
S. Charpenay ◽  
J. A. Rifkin ◽  
Z. Z. Yu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Boundary Energy ◽  
Alloy System ◽  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Surface Energies ◽  
Embedded Atom ◽  
Dynamics Simulations ◽  
Anti Phase Boundary

ABSTRACTCalculations of the surface free energy and anti-phase boundary energy as a function of low index orientations and temperature have been determined for equiatomic perfectly ordered bcc NiAl via molecular dynamics computer simulations. The simulations utilized an Embedded Atom Method calculation of the interatomic potentials and volume forces in the Ni-As alloy system. Values of about 0.95, 1.6, 1.9 and 2.0 J/m2 were found for surface energies of the {100}, {110}, {112} and {111} orientations:, respectively. APB energies of about 0.24 and 0.38 J/m2 were determined for {110} and {112} boundaries, respectively. In addition, we have examined the phase stability and relative energies of the ordered bcc, fcc and bct phases at low temperature, and find a bct phase with c/a = 1.32 slightly lower in energy than the bcc, presaging the martensitic transformation that occurs at finite temperatures in more nickel rich alloys.

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.

Stability of tight-packed metals with the embedded-atom method

1992 ◽  
Vol 7 (4) ◽  
pp. 883-887 ◽  
Author(s):  
R.A. Johnson
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Cohesive Energy ◽  
Input Data ◽  
Formation Energy ◽  
Stacking Faults ◽  
Embedded Atom Method ◽  
Distance Curve ◽  
Embedded Atom ◽  
Cutoff Distance

Relationships between embedded-atom method parameters and the energies of fcc-hcp stability and intrinsic and extrinsic fcc stacking-faults were studied for Cu, Ag, Au, Ni, Pd, and Pt. It was found that the relative magnitudes of these energies for different metals are determined primarily by the physical input data and are almost independent of the cutoff distance and the functions used in the model. These energies increase with increasing vacancy formation energy, decrease with increasing atomic volume and shear modulus, and are almost independent of variations in the cohesive energy and the bulk modulus. However, the shape of the energy versus cutoff distance curve is almost the same for all six metals and is determined primarily by the cutoff distance and the functions used in the model. The shape for a given model is almost independent of the physical input parameters used for fitting to specific metals, can yield either positive or negative values (determined primarily by the cutoff distance), and is similar for all three energies.

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.

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