Communication: Striking dependence of diffusion kinetics in Ag–Cu nanoalloys upon composition and quantum effects

Asgari, Mehdi; Negreiros, Fábio R.; Sementa, Luca; Barcaro, Giovanni; Behnejad, Hassan; Fortunelli, Alessandro

doi:10.1063/1.4891564

Cited by 10 publications

(6 citation statements)

References 40 publications

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“…A few studies investigated the dynamics of chemical reordering, targeting only subnanometer nanoalloys. 31,32 They identified two possible rearrangement mechanisms: surface peeling and atomic inter-diffusion. 33 The former consists of elementary steps of surface diffusion and displacements and leads to segregated-segregated transformations.…”

Section: Introductionmentioning

confidence: 99%

The effect of chemical ordering and lattice mismatch on structural transitions in phase segregating nanoalloys

Rossi

Baletto

2017

Phys. Chem. Chem. Phys.

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We elucidate the effect of lattice mismatch and chemical ordering on structural transitions in bimetallic nanoalloys of ∼1.5 nm. We show that collective screw dislocation motions happen in small mismatch shell@core systems while strongly mismatched ones favour incomplete outer shell rearrangements. Cooperative transitions can also become hindered when the chemical ordering breaks the geometrical symmetry. Escaping from an unfavourable morphological basin occurs first via re-arrangements of the geometry and then changes towards a better chemical pattern. We observe that the chemical re-ordering mechanisms are independent of system composition and stoichiometry but hinge on the initial and final chemical arrangements.

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Section: Introductionmentioning

confidence: 99%

The effect of chemical ordering and lattice mismatch on structural transitions in phase segregating nanoalloys

Rossi

Baletto

2017

Phys. Chem. Chem. Phys.

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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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“…Asagari et al [63] determined the kinetic rates of atomistic inter-diffusion mechanisms leading to putative global minima in metastable configurations exhibiting single-atom misplacements due, e.g., to imperfect synthesis. These rates vary with the adopted reordering behaviour by 10-11 orders of magnitude in rates at room temperature in narrow intervals of size and composition.…”

Section: Reassessment Of Some Experimental Results: Case Of the Cu-ag...mentioning

confidence: 99%

Alloying nanoparticles by discharges in liquids: a quest for metastability

Nominé¹,

Tarasenka²,

Nevar³

et al. 2021

Plasma Phys. Control. Fusion

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Resorting to ultrafast processes to synthesize alloy nanoparticles far from thermodynamic equilibrium is subjected to phase transformations that keep particles at a given temperature for periods of time that are usually long with respect to the process pulse durations. Then, reaching non-equilibrium conditions is not straightforwardly associated with the process, as fast as it can be, but rather to heat transfer mechanisms during phase transformations. This latter aspect is dependent on nanoparticle size. Furthermore, other important phenomena, like chemical ordering, are essential to explain the final structure adopted by an alloy nanoparticle. In this work, a specific attention is paid to suspensions submitted either to electrical discharges or to ultrashort laser excitations. After discussing thermodynamic considerations that give the frame beyond which non-equilibrium alloys form, a description of the heating processes at stake is provided. This leads to maximum temperature reached for particles with nanometric sizes and specific conditions to fulfil practically during the quenching step. The way solidification must be processed in that purpose is discussed next. The example of the Cu-Ag system is finally considered to illustrate the advantage of better controlling processes that are currently used to create homogeneously-alloyed nanoparticles made of immiscible elements, but also to show the actual limitations of these approaches.

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Communication: Striking dependence of diffusion kinetics in Ag–Cu nanoalloys upon composition and quantum effects

Abstract: A refined polarizable water model for the coarse-grained MARTINI force field with long-range electrostatic

Cited by 10 publications

References 40 publications

The effect of chemical ordering and lattice mismatch on structural transitions in phase segregating nanoalloys

The effect of chemical ordering and lattice mismatch on structural transitions in phase segregating nanoalloys

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

Alloying nanoparticles by discharges in liquids: a quest for metastability

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