Kinetic Monte Carlo simulation of surface segregation in Pd–Cu alloys

Cheng, Feng; He, Xiang; Chen, Zhao‐Xu; Huang, Yugai

doi:10.1016/j.jallcom.2015.05.286

Cited by 20 publications

(26 citation statements)

References 56 publications

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“…Literature reporting experimental measurements or theoretical calculations for surface segregation of Pd alloys at various temperatures, is restricted to a selection of binary alloys, [42][43][44][45][46][47][48][49][50][51][52]. Literature results of surface segregation of the 1 st atomic layer on (111) plane are summarized in Table 5, to compare with calculations in the present research.…”

Section: Segregation In Vacuummentioning

confidence: 99%

“…However, SRO usually occurs in real alloys, which modifies the probability of nearest neighbours, as well as the segregation enthalpy and entropy. For example, a "Pd cluster" structure has been reported on the surface of Pd-Cu alloy upon segregation at 600 K [49]. In particular, for Pd-Ag and Pd-Cu alloys with negative ω, atoms of the same element tend to form clusters, then the model will underestimate the segregation enthalpy, as well as the surface fraction.…”

Section: Segregation In Vacuummentioning

confidence: 99%

“…Co-adsorption of H and CO is a competitive process [49], which means that the total adsorbate coverage of different gases is basically a constant:…”

Section: Effect Of Co-adsorptionmentioning

confidence: 99%

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Modelling of surface segregation for palladium alloys in vacuum and gas environments

Zhao

Sloof

Böttger

2018

International Journal of Hydrogen Energy

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Surface segregation of a series of forty Palladium-based binary alloys has been investigated using a thermodynamic model based on an atom exchange approach. Their surface segregation behaviour, both in vacuum and in gas environments, were comprehensively estimated. The calculated results are in good agreement with the available experimental and computational data reported in literatures. Effects of mixing enthalpy, temperature, crystal orientation on the surface, elastic strain energy, adsorption and absorption of gases like H 2 , O 2 , CO have been discussed in detail. These results can be considered as basic guidelines to design novel Pd alloys for hydrogen separation membranes, sensors or catalysts. The model itself also offers a convenient and accurate routine to predict the surface segregation of other than Pd-based binary alloys in different gas atmospheres.

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Section: Segregation In Vacuummentioning

confidence: 99%

Section: Segregation In Vacuummentioning

confidence: 99%

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Modelling of surface segregation for palladium alloys in vacuum and gas environments

Zhao

Sloof

Böttger

2018

International Journal of Hydrogen Energy

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“…The temperature is set at 700 K to allow sufficient restructuring events to occur within the 20 ns period. We perform transition state modeling of representative restructuring events for each class, using the Atomic Simulation Environment (ASE) 16,17 with our custom GP calculator. 12 We use the fast inertial relaxation engine (FIRE) algorithm, 18 a damped dynamics method, for all optimizations.…”

Section: Event Energeticsmentioning

confidence: 99%

Evolution of Metastable Structures at Bimetallic Surfaces from Microscopy and Machine-Learning Molecular Dynamics

et al. 2020

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Restructuring of interfaces plays a crucial role in materials science and heterogeneous catalysis. Bimetallic systems, in particular, often adopt very different composition and morphology at surfaces compared to the bulk. For the first time, we reveal a detailed atomistic picture of long-timescale restructuring of Pd deposited on Ag, using microscopy, spectroscopy, and novel simulation methods. By developing and performing accelerated machine-learning molecular dynamics followed by an automated analysis method, we discover and characterize previously unidentified surface restructuring mechanisms in an unbiased fashion, including Pd-Ag place exchange and Ag pop-out, as well as step ascent and descent. Remarkably, layer-by-layer dissolution of Pd into Ag is always preceded by an encapsulation of Pd islands by Ag, resulting in a significant migration of Ag out of the surface and a formation of extensive vacancy pits within a period of microseconds. These metastable structures are of vital catalytic importance, as Ag-encapsulated Pd remains much more accessible to reactants than bulk-dissolved Pd. Our approach is broadly applicable to complex multimetallic systems and enables the previously intractable mechanistic investigation of restructuring dynamics at atomic resolution. File list (2) download file view on ChemRxiv 061220_PdAg_ESI_v5.pdf (13.63 MiB) download file view on ChemRxiv 061220_PdAg_Main_v5.pdf (11.39 MiB)

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“…19,20 These observations suggest pretreatment as a promising way of activating or deactivating bimetallic catalysts. 8 Mechanistic and kinetic studies of surface restructuring at the atomic level are challenging and scarce, [21][22][23][24][25][26][27] but they provide a foundation for engineering surface ensemble distributions toward optimal activity-selectivity balance. 28 Density functional theory enables exploration of reaction pathways on model surfaces, 29 but its high computational cost precludes its use for dynamical simulation of larger systems beyond hundred picoseconds.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Metastable Structures in Bimetallic Catalysts from Microscopy and Machine-Learning Molecular Dynamics

Lim¹,

Vandermause²,

Spronsen³

et al. 2020

Preprint

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Restructuring of interface plays a crucial role in materials science and heterogeneous catalysis. Bimetallic systems, in particular, often adopt very different composition and morphology at surfaces compared to the bulk. For the first time, we reveal a detailed atomistic picture of the long-timescale restructuring of Pd deposited on Ag, using microscopy, spectroscopy, and novel simulation methods. Encapsulation of Pd by Ag always precedes layer-by-layer dissolution of Pd, resulting in significant Ag migration out of the surface and extensive vacancy pits. These metastable structures are of vital catalytic importance, as Ag-encapsulated Pd remains much more accessible to reactants than bulk-dissolved Pd. The underlying mechanisms are uncovered by performing fast and large-scale machine-learning molecular dynamics, followed by our newly developed method for complete characterization of atomic surface restructuring events. Our approach is broadly applicable to other multimetallic systems of interest and enables the previously impractical mechanistic investigation of restructuring dynamics.

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Kinetic Monte Carlo simulation of surface segregation in Pd–Cu alloys

Cited by 20 publications

References 56 publications

Modelling of surface segregation for palladium alloys in vacuum and gas environments

Modelling of surface segregation for palladium alloys in vacuum and gas environments

Evolution of Metastable Structures at Bimetallic Surfaces from Microscopy and Machine-Learning Molecular Dynamics

Evolution of Metastable Structures in Bimetallic Catalysts from Microscopy and Machine-Learning Molecular Dynamics

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