Monte Carlo Simulations of Solute-Atom Segregation at [001] Symmetrical Twist Boundaries in the Ni-Pi System

1992 ◽  
Vol 278 ◽  
Author(s):  
D. Udler ◽  
D. N. Seidman
Keyword(s):  
Phase Diagram ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Solute Atom ◽  
Atom Concentration ◽  
Embedded Atom ◽  
Pt Alloy ◽  
Solute Atoms ◽  
Rich Side ◽  
Twist Boundaries

AbstractAtomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have been carried out for a series of symmetrical [001] twist boundaries in Pt-3 at.% Ni and Ni-3 at.% Pt alloy bicrystals at 850 K throughout the misorientation range 0° to 45°. The results demonstrate enhancement of the solute-atom concentration at twist boundaries for both alloys; the interfacial Gibbsian excess is a factor of two greater on the Ni-rich side of the phase diagram. The spatial distributions of solute atoms in the vicinity of the interfaces are found to be markedly different on the two sides of the Ni-Pt phase diagram. For low-angle boundaries on the Pt-rich side solute atoms tend to segregate in hourglass-like regions along the cores of the primary grain boundary screw dislocations, while in the case of Ni-3 at.% Pt they occupy bipyramidal regions centered on the cells of the dislocation grid. The former behavior explains the oscillatory solute-atom concentration profiles nomnal to the plane of an intetface.

Solute-atom segregation is high-angle (002) twist boundaries in dilute Au–Pt alloys

1995 ◽  
Vol 10 (8) ◽  
pp. 1933-1941 ◽  
Author(s):  
D. Udler ◽  
D.N. Seidman
Keyword(s):  
Phase Diagram ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Solute Atom ◽  
Perfect Crystal ◽  
High Angle ◽  
Structural Units ◽  
Crystal Type ◽  
Rich Side ◽  
Twist Boundaries

Solute-atom segregation is studied by Monte Carlo simulations for three high-angle symmetrical (002) twist boundaries in Au-1 at. % Pt and Pt-1 at. % Au alloys at T = 850 K. It complements our previous study, that focused mainly on low-angle boundaries in the same alloys. Solute enhancement occurs on the Pt-rich side of the phase diagram, while on the Au-rich side net depletion in solute is observed. Following the trend observed for low-angle boundaries, Au as a solute prefers the structural units of the perfect crystal type, while Pt as a solute is depleted at those sites. The solutc concentration at structural units depends on the planar fraction of those units in the boundary.

Superficial Phase Transitions in Nanoalloys

2011 ◽  
Vol 172-174 ◽  
pp. 658-663 ◽  
Author(s):  
Mohamed Briki ◽  
Jérôme Creuze ◽  
Fabienne Berthier ◽  
Bernard Legrand
Keyword(s):  
Phase Diagram ◽  
Monte Carlo ◽  
Phase Transitions ◽  
Monte Carlo Simulations ◽  
Bimetallic Nanoparticles ◽  
Bimodal Distribution ◽  
The Other ◽  
Nanoparticle Assembly ◽  
Interatomic Potentials ◽  
Grand Canonical

In order to build the phase diagram of Cu-Ag nanoalloys, we study a 405-atom nanoparticle by means of Monte Carlo simulations with relaxations usingN-body interatomic potentials. We focus on a range of nominal concentrations for which the cluster core remains Cu-pure and the (001) facets of the outer shell exhibit two original phenomena. Within the (N,mAg-mCu,P,T) ensemble, a structural and chemical bistability is observed, which affects all the (001) facets together. For a nanoparticle assembly, this will result in a bimodal distribution of clusters, some of them having their (001) facets Cu-rich with the usual square shape, the other ones having their (001) facets Ag-rich with a diamond shape. This bistability is replaced in the (NAg,NCu,P,T) ensemble by a continuous evolution of both the structure and the concentration of the (001) facets from Cu-rich square-shaped to Ag-rich diamond-shaped facets as the number of Ag atoms increases. For a nanoparticle assembly, this will result in an unimodal distribution of the cluster population concerning the properties of the (001) facets. This comparison between pseudo grand canonical and isothermal-isobaric results shows that the distribution of a population of bimetallic nanoparticles depends strongly on the conditions under it is elaborated.

ASYMMETRIC EXCLUSION PROCESSES ON LATTICES WITH A JUNCTION: THE EFFECT OF UNEQUAL INJECTION RATES

2009 ◽  
Vol 20 (06) ◽  
pp. 967-978 ◽  
Author(s):  
XIONG WANG ◽  
RUI JIANG ◽  
KATSUHIRO NISHINARI ◽  
MAO-BIN HU ◽  
QING-SONG WU
Keyword(s):  
Phase Diagram ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Exclusion Processes ◽  
Asymmetric Exclusion ◽  
Asymmetric Exclusion Processes ◽  
Injection Rates

Asymmetric exclusion processes (ASEP) on lattices with a junction, in which two or more parallel lattice branches combine into a single one, is important as a model for complex transport phenomena. This paper investigates the effect of unequal injection rates in ASEP with a junction. It is a generalization of the work of Pronina and Kolomeisky [J. Stat. Mech. P07010 (2005)], in which only equal injection rates are considered. It is shown that the unequal rates give rise to new phases and the phase diagram structure is qualitatively changed. The phase diagram and the density profiles are investigated by using Monte Carlo simulations, mean field approximation and domain wall approach. The analytical results are in good agreement with Monte Carlo simulations.

ATOMIC RESOLUTION STUDIES OF SOLUTE-ATOM SEGREGATION AT GRAIN BOUNDARIES : EXPERIMENTS AND MONTE CARLO SIMULATIONS

1990 ◽  
Vol 51 (C1) ◽  
pp. C1-47-C1-57 ◽  
Author(s):  
D. N. SEIDMAN ◽  
J. G. HU ◽  
S.-M. KUO ◽  
B. W. KRAKAUER ◽  
Y. OH ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Grain Boundaries ◽  
Solute Atom ◽  
Atomic Resolution
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