ORCID Profile
0000-0003-2764-356X
Current Organisation
Fritz-Haber-Institut der Max-Planck-Gesellschaft
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Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3NH00140G
Abstract: Size-dependent diffusion of supported faceted nanoclusters is mediated by disassembly & reassembly of outer layers of facets. A mean-field picture (random independent motion of surface atoms) fails to capture behavior.
Publisher: AIP Publishing
Date: 27-11-2017
DOI: 10.1063/1.5008424
Abstract: The dynamics of nanoscale clusters can be distinct from macroscale behavior described by continuum formalisms. For diffusion of 2D clusters of N atoms in homoepitaxial systems mediated by edge atom hopping, macroscale theory predicts simple monotonic size scaling of the diffusion coefficient, D
Publisher: AIP Publishing
Date: 08-03-2023
DOI: 10.1063/5.0138266
Abstract: Shape stability is key to avoiding degradation of performance for metallic nanocrystals synthesized with facetted non-equilibrium shapes to optimize properties for catalysis, plasmonics, and so on. Reshaping of facetted nanocrystals is controlled by the surface diffusion-mediated nucleation and growth of new outer layers of atoms. Kinetic Monte Carlo (KMC) simulation of a realistic stochastic atomistic-level model is applied to precisely track the reshaping of Pd octahedra and nanocubes. Unexpectedly, separate constrained equilibrium Monte Carlo analysis of the free energy profile during reshaping reveals a fundamental failure of the classical nucleation theory (CNT) prediction for the reshaping barrier and rate. Why? Nucleation barriers can be relatively low for these processes, so the system is not locally equilibrated before crossing the barrier, as assumed in CNT. This claim is supported by an analysis of a first-passage problem for reshaping within a master equation framework for the model that reasonably captures the behavior in KMC simulations.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0NR07024F
Abstract: Metal nanoclusters encapsulated beneath the graphite surface present novel surface nanostructures and open opportunities to investigate and control interfacial properties.
Publisher: American Chemical Society (ACS)
Date: 04-06-2019
DOI: 10.1021/ACS.CHEMREV.8B00582
Abstract: Self-assembly of supported 2D or 3D nanocrystals (NCs) by vacuum deposition and of 3D NCs by solution-phase synthesis (with possible subsequent transfer to a support) produces intrinsically nonequilibrium systems. In idual NCs can have far-from-equilibrium shapes and composition profiles. The free energy of NC ensembles is lowered by coarsening which can involve Ostwald ripening or Smoluchowski ripening (NC diffusion and coalescence). Preservation of in idual NC structure and inhibition of coarsening are key, e.g., for avoiding catalyst degradation. This review focuses on postsynthesis evolution of metallic NCs. Atomistic-level modeling typically utilizes stochastic lattice-gas models to access appropriate time and length scales. However, predictive modeling requires incorporation of realistic rates for relaxation mechanisms, e.g., periphery diffusion and intermixing, in numerous local environments (rather than the use of generic prescriptions). Alternative coarse-grained modeling must also incorporate appropriate mechanisms and kinetics. At the level of in idual NCs, we present analyses of reshaping, including sintering and pinch-off, and of compositional evolution in a vacuum environment. We also discuss modeling of coarsening including diffusion and decay of in idual NCs and unconventional coarsening processes. We describe high-level modeling integrated with scanning tunneling microscopy (STM) studies for supported 2D epitaxial nanoclusters and developments in modeling for 3D NCs motivated by in situ transmission electron microscopy (TEM) studies.
Publisher: IOP Publishing
Date: 05-2020
Abstract: We use a variety of experimental techniques to characterize Cu clusters on bulk MoS 2 formed via physical vapor deposition of Cu in ultrahigh vacuum, at temperatures ranging from 300 K to 900 K. We find that large facetted clusters grow at elevated temperatures, using high Cu exposures. The cluster size distribution is bimodal, and under some conditions, large clusters are surrounded by a denuded zone. We propose that defect-mediated nucleation, and coarsening during deposition, are both operative in this system. At 780 K, a surprising type of facetted cluster emerges, and at 900 K this type predominates: pyramidal clusters with a triangular base, exposing (311) planes as side facets. This is a growth shape, rather than an equilibrium shape.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR05845A
Abstract: Complex oscillatory decay in diffusivity of epitaxially supported 3D fcc metal nanoclusters contrasting simple monotonic decay on the macroscale.
Publisher: American Chemical Society (ACS)
Date: 22-02-2018
Publisher: American Chemical Society (ACS)
Date: 08-07-2020
Publisher: IOP Publishing
Date: 10-08-2020
Publisher: American Chemical Society (ACS)
Date: 19-03-2019
Publisher: American Chemical Society (ACS)
Date: 07-07-2021
Publisher: Elsevier BV
Date: 10-2020
Publisher: American Chemical Society (ACS)
Date: 20-02-2020
Publisher: American Physical Society (APS)
Date: 06-2020
No related grants have been discovered for King Chun Lai.