| 239 |
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nanoparticle, while the copper atoms which have local icosahedral |
| 240 |
|
ordering are distributed more evenly throughout the nanoparticles. |
| 241 |
|
Silver, since it has a lower surface free energy than copper, tends to |
| 242 |
< |
coat the skins of the mixed particles. This is true even for |
| 242 |
> |
coat the skins of the mixed particles.\cite{Zhu:1997lr} This is true even for |
| 243 |
|
bimetallic particles that have been prepared in the Ag (core) / Cu |
| 244 |
|
(shell) configuration. Upon forming a liquid droplet, approximately 1 |
| 245 |
|
monolayer of Ag atoms will rise to the surface of the particles. This |
| 246 |
< |
can be seen visually in figure \ref{fig:cross_sections}. Bond order |
| 247 |
< |
parameters for surface atoms are averaged only over the neighboring |
| 246 |
> |
can be seen visually in figure \ref{fig:cross_sections}. This observation is consistent with previous experimental and theoretical studies on bimetallic alloys composed of noble metals.\cite{MainardiD.S._la0014306,HuangS.-P._jp0204206,Ramirez-Caballero:2006lr} |
| 247 |
> |
Bond order parameters for surface atoms are averaged only over the neighboring |
| 248 |
|
atoms, so packing constraints that may prevent icosahedral ordering |
| 249 |
|
around silver in the bulk are removed near the surface. It would |
| 250 |
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certainly be interesting to see if the relative tendency of silver and |
