1 |
chuckv |
3208 |
\title{Simulations of laser-induced glass formation in Ag-Cu nanoparticles} |
2 |
|
|
\author{Charles F. Vardeman~II and J. Daniel Gezelter \\ |
3 |
|
|
Department of Chemistry and Biochemistry\\ |
4 |
|
|
University of Notre Dame\\ |
5 |
|
|
Notre Dame, Indiana 46556} |
6 |
|
|
|
7 |
|
|
\date{\today} |
8 |
|
|
\maketitle |
9 |
|
|
\begin{abstract} |
10 |
gezelter |
3247 |
Using Molecular Dynamics simulations, we have simulated the rapid |
11 |
|
|
cooling experienced by bimetallic nanoparticles following laser |
12 |
|
|
excitation at the plasmon resonance and find evidence that glassy |
13 |
|
|
beads, specifically Ag-Cu bimetallic particles at the eutectic |
14 |
|
|
composition (60\% Ag, 40\% Cu), can be formed during these |
15 |
|
|
experiments. The bimetallic nanoparticles are embedded in an implicit |
16 |
|
|
solvent with a viscosity tuned to yield cooling curves that match the |
17 |
|
|
experimental cooling behavior as closely as possible. Since the |
18 |
|
|
nanoparticles have a large surface-to-volume ratio, experimentally |
19 |
|
|
realistic cooling rates are accessible via relatively short |
20 |
|
|
simulations. The presence of glassy structural features was verified |
21 |
|
|
using bond orientational order parameters which are sensitive to the |
22 |
|
|
formation of local icosahedral ordering in condensed phases. As the |
23 |
|
|
particles cool from the liquid droplet state into glassy beads, a |
24 |
|
|
silver-rich monolayer develops on the outer surface, and local |
25 |
|
|
icosahedra can develop around the silver atoms in this monolayer. |
26 |
|
|
However, we observe a strong preference for the local icosahedral |
27 |
|
|
ordering around the copper atoms in the particles. As the particles |
28 |
|
|
cool, these local icosahedral structures grow to include a larger |
29 |
|
|
fraction of the atoms in the nanoparticle, eventually leading to a |
30 |
|
|
glassy nanosphere. |
31 |
chuckv |
3208 |
\end{abstract} |