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Published on: December 6, 2021
Structure and chemical ordering in CoPt nanoalloys
G Rossi1, R Ferrando, C Mottet
1" INFM and IMEM/CNR, Dipartimento di Fisica dell'Universitá di Genova, via Dodecaneso 33, 16146 Genova, Italy.
Faraday Discussions
|May 2, 2008
Summary
This study explores cobalt-platinum (CoPt) nanocluster structures. CoPt nanoclusters exhibit unique atomic arrangements and chemical ordering, transitioning from icosahedral to decahedral symmetries with increasing size.
Area of Science:
- Materials Science
- Computational Chemistry
- Nanotechnology
Background:
- Understanding the structure and chemical ordering of bimetallic nanoclusters is crucial for their application in catalysis and magnetic storage.
- Cobalt-Platinum (CoPt) nanoclusters are of particular interest due to their unique magnetic and catalytic properties.
Purpose of the Study:
- To investigate the atomic structure and chemical ordering of CoPt nanoclusters in the 1-3 nm size range.
- To determine the influence of cluster size on structural transitions and chemical ordering.
- To explore the surface segregation behavior of cobalt and platinum atoms.
Main Methods:
- Global optimization methods were employed to determine stable atomic structures.
- Monte Carlo simulations using a many-body potential derived from the tight-binding model were utilized.
- Canonical Monte Carlo simulations were used to study the L1(0)-ordered/disordered transition.
Main Results:
- Smaller CoPt nanoclusters (N < 100) adopt polyicosahedral-like structures with specific surface chemical configurations.
- A transition to decahedral symmetry occurs around N = 100 atoms, exhibiting a pseudo L1(0) ordered phase.
- For larger clusters (201 < N < 1289), the critical disordering temperature of the L1(0) phase decreases with increasing cluster size.
- Cobalt surface segregation was observed, particularly at edges and facets, depending on cluster size and symmetry.
Conclusions:
- CoPt nanoclusters exhibit size-dependent structural and chemical ordering transitions.
- The L1(0) ordering is sensitive to cluster size, with a decreasing critical temperature for larger clusters.
- Surface segregation of cobalt plays a significant role in the overall cluster properties.
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