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Thermodynamics of CuPt nanoalloys

Rossi, K., Partay, L., Csanyi, G. and Baletto, F. (2018) Thermodynamics of CuPt nanoalloys. Scientific Reports, 8. 9150. ISSN 2045-2322

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To link to this item DOI: 10.1038/s41598-018-27308-1

Abstract/Summary

The control of structural and chemical transitions in bimetallic nanoalloys at finite temperatures is one of the challenges for their use in advanced applications. Comparing Nested Sampling and Molecular Dynamics simulations, we investigate the phase changes of CuPt nanoalloys with the aim to elucidate the role of kinetic effects during their solidification and melting processes. We find that the quasi-thermodynamic limit for the nucleation of (CuPt)309 is 965 ± 10 K, but its prediction is increasingly underestimated when the system is cooled faster than 109 K/s. The solidified nanoparticles, classified following a novel tool based on Steinhardt parameters and the relative orientation of characteristic atomic environments, are then heated back to their liquid phase. We demonstrate the kinetic origin of the hysteresis in the caloric curve as (i) it closes for rates slower than 108 K/s, with a phase change temperature of 970 K ± 25 K, in very good agreement with its quasi-thermodynamic limit; (ii) the process happens simultaneously in the inner and outer layers; (iii) an onion-shell chemical order - Cu-rich surface, Pt-rich sub-surface, and mixed core - is always preserved.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:77734
Publisher:Nature Publishing Group

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