An Atomistic Study of Surface Vacancy Diffusion

1993 ◽  
Vol 311 ◽  
Author(s):  
L. Zhao ◽  
R. Najafabadi ◽  
D. J. Srolovtz
Keyword(s):  
Film Growth ◽  
Diffusion Mechanism ◽  
Thin Film Growth ◽  
Atomistic Simulations ◽  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Vacancy Diffusion ◽  
Embedded Atom ◽  
Surface Vacancy ◽  
Atomistic Study

ABSTRACTDiffusion of atoms and molecules on surfaces plays an important role in the growth of thin films. In the present study, the surface vacancy diffusion on Cu and Ni (100) and (111) planes is investigated via atomistic simulations. This investigation is performed using the Embedded Atom Method (EAM) interatomic potentials and the finite temperature properties are determined within the local harmonic and quasiharmonic frameworks. This study helps reveal fundamentals of surface vacancy diffusion in the thin film growth. Our results show that the vacancy diffusion is important on (100) surface but it is not the dominant diffusion mechanism on (111) plane.

Atomistic Simulations of fcc Pt75Ni25 and Pt75Re25 Cubo-octahedral Nanoparticles

2004 ◽  
Vol 818 ◽  
Author(s):  
Guofeng Wang ◽  
M.A. Van Hove ◽  
P.N. Ross ◽  
M.I. Baskes
Keyword(s):  
Sandwich Structure ◽  
Surface Segregation ◽  
Atomistic Simulations ◽  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Atomic Shell ◽  
Embedded Atom ◽  
The Monte Carlo Method ◽  
Equilibrium Structures ◽  
Modified Embedded Atom Method

AbstractWe have developed interatomic potentials for Pt-Ni and Pt-Re alloys within the modified embedded atom method (MEAM). Furthermore, we applied these potentials to study the equilibrium structures of Pt75Ni25 and Pt75Re25 nanoparticles at T=600 K using the Monte Carlo method. In this work, the nanoparticles are assumed to have disordered fcc cubo-octahedral shapes (terminated by {111} and {100} facets) and contain from 586 to 4033 atoms (corresponding to a diameter from 2.5 to 5 nm). It was found that, due to surface segregation, (1) the Pt75Ni25 nanoparticles form a surface-sandwich structure: the Pt atoms are enriched in the outermost and third atomic shells, while the Ni atoms are enriched in the second atomic shell; (2) the equilibrium Pt75Re25 nanoparticles adopt a core-shell structure: a Pt-enriched shell surrounding a Pt-deficient core.

Methods for Determining Vacancy Formation Thermodynamic

1992 ◽  
Vol 291 ◽  
Author(s):  
L. Zhao ◽  
R. Najafabadl ◽  
D. J. Srolovitz
Keyword(s):  
Vacancy Concentration ◽  
Excess Entropy ◽  
Vacancy Formation ◽  
Atomistic Simulations ◽  
Embedded Atom Method ◽  
Simple Extension ◽  
Interatomic Potentials ◽  
Harmonic Method ◽  
Embedded Atom ◽  
Formation Thermodynamics

ABSTRACTThe vacancy formation thermodynamics in six fcc metals Ag, Au, Cu, Ni, Pd and Pt are determined from atomistic simulations as a function of temperature. This investigation is performed using the Embedded Atom Method interatomic potentials and the finite temperature properties are determined within the local harmonic and the quasiharmonic frameworks. We find that the temperature dependence of the vacancy formation energy can make a significant contribution to the vacancy concentration at high temperatures. An additional goal of the present study is to evaluate the accuracy of the local harmonic method under circumstances in which the excess entropy associated with the formation of a defect is very small. Our data demonstrate that while the errors associated with determining the vacancy formation entropy in the local harmonic model are large, a simple extension to the local harmonic method yields thermodynamic properties comparable to that obtained in the quasiharmonic model, but with much higher computational efficiency.

An embedded-atom method interatomic potential for Pd–H alloys

2008 ◽  
Vol 23 (3) ◽  
pp. 704-718 ◽  
Author(s):  
X.W. Zhou ◽  
J.A. Zimmerman ◽  
B.M. Wong ◽  
J.J. Hoyt
Keyword(s):  
Computational Models ◽  
Mechanical Response ◽  
Hydrogen Diffusion ◽  
Interatomic Potential ◽  
Diffusion Mechanism ◽  
Miscibility Gap ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Formidable Challenge ◽  
Embedded Atom Method Potential

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.

Structure and Elastic Properties of Ni/Cu and Ni/Au Multilayers

1992 ◽  
Vol 291 ◽  
Author(s):  
Ademola Taiwo ◽  
Hong Yan ◽  
Gretchen Kalonji
Keyword(s):  
Phase Transformation ◽  
Elastic Properties ◽  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Multilayer Systems ◽  
Lattice Statics ◽  
Embedded Atom ◽  
Hcp Structure ◽  
Fcc Structure ◽  
Coherent Interfaces

ABSTRACTThe structure and elastic properties of Ni/Cu and Ni/Au multilayer systems are investigated as a function of the number of Ni monolayers built into the systems. We employed lattice statics simulations with the interatomic potentials described by the embedded-atom method. For the Ni/Cu systems, coherent interfaces and FCC structure are maintained, and no elastic anomaly is found. For the Ni/Au systems, when the Ni layers are thick enough, they undergo a strain-induced phase transformation from FCC to HCP structure. An enhancement of Young’s modulus of these systems is found to be associated with this structural change.

scholarly journals Controversy Over Elastic Constants Based on Interatomic Potentials

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
L. G. Zhou ◽  
Hanchen Huang
Keyword(s):  
Elastic Constants ◽  
Necessary Condition ◽  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Embedded Atom

A controversy exists among literature reports of constraints on elastic constants. In particular, it has been reported that embedded atom method (EAM) potentials generally impose three constraints on elastic constants of crystals that are inconsistent with experiments. However, it can be shown that some EAM potentials do not impose such constraints at all. This paper first resolves this controversy by identifying the necessary condition when the constraints exist and demonstrating the condition is physically necessary. Furthermore, this paper reports that these three constraints are eliminated under all conditions, by using response EAM (R-EAM) potentials.

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.

The Ehrlich-Schwoebel Effect for Vacancies: Low-Index Faces of Silver

2000 ◽  
Vol 648 ◽  
Author(s):  
Michael I. Haftel
Keyword(s):  
Diffusion Barrier ◽  
Activation Barrier ◽  
Diffusion Barriers ◽  
Step Edge ◽  
Embedded Atom Method ◽  
Vacancy Diffusion ◽  
Exchange Diffusion ◽  
Embedded Atom ◽  
And Diffusion ◽  
Step Edges

AbstractWe employ surface-embedded-atom-method potentials to investigate the diffusion barriers of vacancies diffusing over and near steps on the low index faces of silver. Barriers for vacancy terrace diffusion, diffusion over step-edges, and diffusion along step edges, including around corners, are calculated. Vacancies are significantly less mobile than adatoms and have large Ehrlich-Schwoebel (ES) barriers on all three faces. For Ag(100) the diffusion barrier for vacancies along step-edges is virtually the same (474 meV) as on the terrace. As in diffusion near the step edge, vacancies encounter a significant increase (213 meV) in the activation barrier when diffusing around the corner of a vacancy island (the corner analogue of the ES barrier), but the excess barrier around a kink all but disappears because exchange diffusion is favorable there. The consequences of the vacancy diffusion barriers on 3D pitting and on island diffusion and coarsening are discussed.

Embedded-atom-method interatomic potentials from lattice inversion

2010 ◽  
Vol 22 (37) ◽  
pp. 375503 ◽  
Author(s):  
Xiao-Jian Yuan ◽  
Nan-Xian Chen ◽  
Jiang Shen ◽  
Wangyu Hu
Keyword(s):  
Embedded Atom Method ◽  
Interatomic Potentials ◽  
Embedded Atom
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