dorsal/arxiv
View SchemaMelting in large sodium clusters: An orbital-free molecular dynamics study
| Authors | Andres Aguado, Jose M. Lopez, Julio A. Alonso, M. J. Stott |
|---|---|
| Categories | |
| ArXiv ID | physics/9911042 |
| URL | https://arxiv.org/abs/physics/9911042 |
Abstract
The melting-like transition in sodium clusters Na_N, with N=55, 92, and 142 is studied by using constant-energy molecular dynamics simulations. An orbital-free version of the Car-Parrinello technique is used which scales linearly with system size allowing investigation of the thermal behaviour of large clusters. The ground state isomer of Na_142 (an uncomplete three-shell icosahedron) melts in two steps: the first one (at approx. 240 K) is characterized by the high mobility of the atoms located on the cluster surface; the second, homogeneous melting (at approx. 270 K), involves diffusive motion of all the atoms across the cluster. For the case of Na_92, the icosahedral structure has a larger number of surface vacancies, and melts in two well separated steps, surface melting at approx. 130 K and homogeneous melting at approx. 240 K. Na_55, a complete two-shell icosahedron, melts in a single stage at approx. 190 K. Our results on homogeneous melting for Na_142 and Na_92 are in excellent agreement with recent experimental determinations of melting temperatures and latent heats. However, the experimentally observed enhancement of the melting temperature around N=55 is not reproduced by the calculations.
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"abstract": "The melting-like transition in sodium clusters Na_N, with N=55, 92, and 142\nis studied by using constant-energy molecular dynamics simulations. An\norbital-free version of the Car-Parrinello technique is used which scales\nlinearly with system size allowing investigation of the thermal behaviour of\nlarge clusters. The ground state isomer of Na_142 (an uncomplete three-shell\nicosahedron) melts in two steps: the first one (at approx. 240 K) is\ncharacterized by the high mobility of the atoms located on the cluster surface;\nthe second, homogeneous melting (at approx. 270 K), involves diffusive motion\nof all the atoms across the cluster. For the case of Na_92, the icosahedral\nstructure has a larger number of surface vacancies, and melts in two well\nseparated steps, surface melting at approx. 130 K and homogeneous melting at\napprox. 240 K. Na_55, a complete two-shell icosahedron, melts in a single stage\nat approx. 190 K. Our results on homogeneous melting for Na_142 and Na_92 are\nin excellent agreement with recent experimental determinations of melting\ntemperatures and latent heats. However, the experimentally observed enhancement\nof the melting temperature around N=55 is not reproduced by the calculations.",
"arxiv_id": "physics/9911042",
"authors": [
"Andres Aguado",
"Jose M. Lopez",
"Julio A. Alonso",
"M. J. Stott"
],
"categories": [
"physics.atm-clus",
"cond-mat"
],
"title": "Melting in large sodium clusters: An orbital-free molecular dynamics study",
"url": "https://arxiv.org/abs/physics/9911042"
},
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