Modeling of Ir adatoms on Ir surfaces
- Institute of Physics, Academia Sinica, Nankang, Taipei, 11529 Taiwan, Republic of (China)
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
We used the embedded-atom method potential to study the structures, adsorption energies, binding energies, migration paths, and energy barriers of the Ir adatom and small clusters on fcc Ir (100), (110), and (111) surfaces. We found that the barrier for single-adatom diffusion is lowest on the (111) surface, higher on the (110) surface, and highest on the (100) surface. The exchange mechanisms of adatom diffusion on (100) and (110) surfaces are energetically favored. On all three Ir surfaces, Ir{sub 2} dimers with nearest-neighbor spacing are the most stable. On the (110) surface, the Ir{sub 2} dimer diffuses collectively along the {l_angle}110{r_angle} channel, while motion perpendicular to the channel walls is achieved by successive one-atom and correlated jumps. On (111) surface, the Ir{sub 2} dimer diffuses in a zigzag motion on hcp and fcc sites without breaking into two single atoms. On the (100) surface, diffusion of the Ir{sub 2} dimer is achieved by successive one-atom exchange with the substrate atom accompanying by a 90{degree} rotation of the Ir{sub 2} dimer. This mechanism has a surprisingly low activation energy of 0.65 eV, which is 0.14 eV lower than the energy for single adatom exchange on the (100) surface. Trimers were found to have a one-dimensional (1D) structure on (100) and (110) surfaces, and a 2D structure on the (111) surface. The observed abrupt drop of the diffusion barrier of tetramer, {ital I}{sub {gamma}{sub 4}} on the Ir (111) surface was confirmed theoretically. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 404039
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 23 Vol. 54; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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