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.

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.

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.

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.

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

Atomistic Simulations of the Mechanical Response of Copper/Polybutadiene Joints under Stress

2009 ◽  
Vol 1224 ◽  
Author(s):  
Fidel Orlando Valega Mackenzie ◽  
Barend J. Thijsse
Keyword(s):  
Mechanical Response ◽  
Polymer System ◽  
Atomistic Simulations ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Numerical Studies ◽  
Universal Force Field ◽  
Dynamics Simulations ◽  
Metal Melting Point ◽  
Metal Polymer

AbstractMetal/polymer system joints are widely encountered nowadays in microscopic structures such as displays and microchips. In several critical cases they undergo thermal and mechanical loading, with contact failure due to fracture as a possible consequence. Because of their variety in nature and composition metal/polymer joints have become major challenges for experimental, theoretical, and numerical studies. Here we report on results of molecular dynamics simulations carried out to study the mechanical response of a metal/polymer joint, in this case the Cu/polybutadiene model system. The behavior of Cu and the cross-linked polybutadiene are modeled, respectively, by the Embedded Atom Method (EAM) and the Universal Force Field (UFF). Loading is applied under compression. Different potentials are used to describe the interactions in the metal/polymer interface, which allows us to qualitatively analyze possible mechanisms of failure in these joints, below the metal melting point and above the polymer glass transition temperatures.

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