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This content will become publicly available on February 22, 2019

Title: Modeling of Diffusivity for 2D Vacancy Nanopits and Comparison with 2D Adatom Nanoislands on Metal(100) Surfaces Including Analysis for Ag(100)

Diffusion coefficients, D N, for 2D vacancy nanopits are compared with those for 2D homoepitaxial adatom nanoislands on metal(100) surfaces, focusing on the variation of DN with size, N. Here, N is measured in missing atoms for pits and adatoms for islands. Analysis of D N is based on kinetic Monte Carlo simulations of a tailored stochastic lattice-gas model, where pit and island diffusion are mediated by periphery diffusion, i.e., by edge atom hopping. Precise determination of D N versus N for typical parameters reveals a cyclical variation with an overall decrease in magnitude for increasing moderate O(10 2) ≤ N ≤ O(10 3). Monotonic decay, D N~ N , is found for N ≥ O(10 2) with effective exponents, β = β eff, for both pits and islands, both well below the macroscopic value of βmacro = 3/2. D N values for vacancy pits are significantly lower (higher) than for adatom islands for moderate N in the case of low (high) kink rounding barrier. However, D N values for pits and islands slowly merge, and β eff → 3/2 for sufficiently large N. The latter feature is expected from continuum Langevin formulations appropriate for large sizes. Finally, we comparemore » predictions from our model incorporating appropriate energetic parameters for Ag(100) with different sets of experimental data for diffusivity at 300 K, including assessment of β eff, for experimentally observed sizes N from ~100 to ~1000.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Iowa State Univ., Ames, IA (United States). Dept. of Physics & Astronomy
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Chemistry, and Dept. of Materials Science & Engineering
  4. Iowa State Univ., Ames, IA (United States). Dept. of Physics & Astronomy, and Dept. of Mathematics
Publication Date:
Report Number(s):
IS-J-9530
Journal ID: ISSN 1932-7447; TRN: US1801661
Grant/Contract Number:
AC02-07CH11358; CHE-1507223
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 21; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1422773