Kinetics of chemical ordering in a Ag-Pt nanoalloy particle via first-principles simulations

Negreiros, Fábio R.; Taherkhani, Farid; Parsafar, Gholamabbas; Caro, A.; Fortunelli, Alessandro

doi:10.1063/1.4759507

Cited by 21 publications

(16 citation statements)

References 42 publications

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“…[113][114][115] Circumventing the limited time scales of atomistic simulations is possible by using rate theories, and only recently such approaches have been applied to the rearrangement kinetics in model nanoalloys. 116,117 By construction, and although some authors have discussed the kinetics of phase transformation in relation to the time needed to cross the nucleation barrier, 110 classical thermodynamic models assume thermal equilibrium and are unable to describe particles explicitly prepared in metastable states. Molecular simulation, on the other hand, can simulate arbitrary systems even away from their known low-energy structure.…”

Section: Discussionmentioning

confidence: 99%

Thermodynamics of nanoalloys

Calvo

2015

Phys. Chem. Chem. Phys.

135

102

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This article reviews recent advances in our understanding of how temperature affects the structure and the phase of multimetallic nanoparticles. Focusing on bimetallic systems, we discuss the interplay of size, shape and chemical order on the stable configurations at thermal equilibrium. Besides some considerations about experimental evidence for thermally-induced transformations, most insight is generally gained from theory and computation. The perspectives offered by mesoscopic approaches (i.e. corrected from the bulk) and atomistic simulations complement each other and often provide detailed information about the respective roles of coordination, composition and more generally surface effects to be evaluated. Order-disorder transitions and the melting phase change are strongly altered in nanoscale systems, and we describe how they possibly impact entire phase diagrams.

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Section: Discussionmentioning

confidence: 99%

Thermodynamics of nanoalloys

Calvo

2015

Phys. Chem. Chem. Phys.

135

102

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“…In the Ag-Pt bimetallic system, the surface energy of Ag is much less than that of Pt, which favors surface enrichment of Ag. [61][62][63][64][65][66][67][68][69] The lattice constant of fcc Ag (4.09 A) is much larger than that of Pt (3.91 A), thus the segregating of Ag atoms from the bulk to the surface will decrease the elastic strain energy. [66][67][68][69] In addition, the positive heat of formation of bulk Ag-Pt alloys also facilitates atomic segregation.…”

Section: Metropolis MC Simulationsmentioning

confidence: 99%

Morphology, dimension, and composition dependence of thermodynamically preferred atomic arrangements in Ag–Pt nanoalloys

et al. 2013

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The present article is on Metropolis Monte Carlo simulations coupled with semiempirical potentials to obtain the thermodynamically preferred configurations of Ag-Pt nanoalloys. The effects of particle size, morphology or alloy composition on the surface segregation and the chemical ordering patterns were investigated. Surface segregation of Ag is observed in all Ag-Pt nanoalloys. Such segregation develops quickly as the increase of particle sizes or global Ag composition. Generally, Ag surface enrichment is more apparent for more open particles except for large sized icosahedron (ICO) nanoalloys. The most energetically favorable chemical ordering patterns gradually evolve from Pt-core/Ag-shell to onion-like structures when the global Ag composition increases. Due to the site preference of Ag segregation, the presence of partly alloyed facets and Ag blocked vertices or edges at low global Ag compositions can modify the electronic and geometric structures on the nanoalloys' surface. The coupling between Pt and Ag sites is a topic of particular interest for catalysis. The detailed atomistic understanding of atomic arrangements in Ag-Pt nanoalloys is essential to intelligently design robust and active nanocatalysts with a low cost.

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“…Interestingly, our conclusion regarding the paths where an adatom is filling a hole on a planar facet of an Au − 20 cluster is quite analogous to their observation of a concerted move sequence between two fcc-minima in Au 55 . We further note that rearrangement paths involving collective moves also appear to be dominant paths in small nanoalloys [131][132][133].…”

Section: Dynamical Evolutionmentioning

confidence: 67%

Exploring energy landscapes at the DFTB quantum level using the threshold algorithm: the case of the anionic metal cluster Au$$_{20}^{-}$$

2021

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We report the combination of the threshold algorithm with the Density Functional based Tight Binding method (DFTB) allowing for the exploration of complex potential energy surfaces and the evaluation of probability flows between their regions, at the quantum level. This original scheme is used to explore the energy landscape of an anionic 20-atom gold cluster, Au − 20 . On the basis of the relevant structures, 19 structural groups are highlighted, all of them being variations about the pyramidal shape : (i) distorted pyramids, (ii) pyramids in which the atom of one of the facets has been removed, leaving a hole, and placed at different positions on the cluster and (iii) pyramids on which an atom located at a vertex has been removed and placed on an edge or on a facet. Upper limits of the energies required to connect the basins of the 19 groups on the potential energy surface are evaluated. Moreover, the attractive basins are identified on the basis of the analysis of the probability flows on the landscape. The comparison of the disconnectivity tree with the results of the flux analysis provides a consistent representation of the Au − 20 basins' proximity. Finally, we show how the new scheme allowed for the identification of counter-intuitive transition pathways.

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Kinetics of chemical ordering in a Ag-Pt nanoalloy particle via first-principles simulations

Cited by 21 publications

References 42 publications

Thermodynamics of nanoalloys

Thermodynamics of nanoalloys

Morphology, dimension, and composition dependence of thermodynamically preferred atomic arrangements in Ag–Pt nanoalloys

Exploring energy landscapes at the DFTB quantum level using the threshold algorithm: the case of the anionic metal cluster Au$$_{20}^{-}$$

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