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Molecular dynamics simulation of UO2 nanocrystals melting

A.S. Boyarchenkov, S.I. Potashnikov, K.A. Nekrasov, A.Ya. Kupryazhkin
Ural Federal University, 620002, Mira street 19, Yekaterinburg, Russia
arXiv:1103.6277v2 [cond-mat.mtrl-sci]

@article{boyarchenkov2011molecular,

   title={Molecular dynamics simulation of UO2 nanocrystals melting},

   author={Boyarchenkov, AS and Potashnikov, SI and Nekrasov, KA and Kupryazhkin, A.Y.},

   journal={Arxiv preprint arXiv:1103.6277},

   year={2011}

}

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In this article we study melting of uranium dioxide (UO2) nanocrystals (NC) isolated in vacuum (i.e. non-periodic boundary conditions) using molecular dynamics (MD) in the approximation of pair potentials and rigid ions. We calculate the size dependence of the temperature and heat of melting, the density jump for crystals of cubic shape and volumes up to 1000 nm^3 (50000 particles). Linear and parabolic extrapolations of these dependences to macroscopic (infinite) size are considered, the parabolic is found to be better suited for the analysis of data on the temperature and the heat of melting. The closest to the modern experimental data estimates of the melting temperature of macrocrystals are obtained using the interaction potentials Goel-08 (2969K), Yakub-09 (3105K) and MOX-07 (3291K). The density jump at melting is well reproduced by Yakub-09 (8.66%) and MOX-07 (7.97%). The heat of fusion for all sets of the potentials considered is found to be underestimated by 50-75%, possibly because of the excluded heat of superionic phase transition.
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