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