dorsal/arxiv
View SchemaMelting behavior of large disordered sodium clusters
| Authors | Andrés Aguado |
|---|---|
| Categories | |
| ArXiv ID | physics/0005045 |
| URL | https://arxiv.org/abs/physics/0005045 |
| DOI | 10.1007/s100530170169 |
Abstract
The melting-like transition in disordered sodium clusters Na_N, with N=92 and 142 is studied by using a first-principles constant-energy molecular dynamics simulation method. Na_142, whose atoms are distributed in two (surface and inner) main shells with different radial distances to the center of mass of the cluster, melts in two steps: the first one, at approx. 130 K, is characterized by a high intrashell mobility of the atoms, and the second, homogeneous melting, at approx. 270 K, involves diffusive motion of all the atoms across the whole cluster volume (both intrashell and intershell displacements are allowed). On the contrary, the melting of Na_92 proceeds gradually over a very wide temperature interval, without any abrupt step visible in the thermal or structural melting indicators. The occurrence of well defined steps in the melting transition is then shown to be related to the existence of a distribution of the atoms in shells. Thereby we propose a necessary condition for a cluster to be considered rigorously amorphouslike (totally disordered), namely that there are no space regions of the cluster where the local value of the atomic density is considerably reduced. Na_92 is the only cluster from the two considered that verifies this condition, so its thermal behavior can be considered as representative of that expected for amorphous clusters. Na_142, on the other hand, has a discernible atomic shell structure and should be considered instead as just partially disordered. The thermal behavior of these two clusters is also compared to that of icosahedral (totally ordered) sodium clusters of the same sizes.
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"abstract": "The melting-like transition in disordered sodium clusters Na_N, with N=92 and\n142 is studied by using a first-principles constant-energy molecular dynamics\nsimulation method. Na_142, whose atoms are distributed in two (surface and\ninner) main shells with different radial distances to the center of mass of the\ncluster, melts in two steps: the first one, at approx. 130 K, is characterized\nby a high intrashell mobility of the atoms, and the second, homogeneous\nmelting, at approx. 270 K, involves diffusive motion of all the atoms across\nthe whole cluster volume (both intrashell and intershell displacements are\nallowed). On the contrary, the melting of Na_92 proceeds gradually over a very\nwide temperature interval, without any abrupt step visible in the thermal or\nstructural melting indicators. The occurrence of well defined steps in the\nmelting transition is then shown to be related to the existence of a\ndistribution of the atoms in shells. Thereby we propose a necessary condition\nfor a cluster to be considered rigorously amorphouslike (totally disordered),\nnamely that there are no space regions of the cluster where the local value of\nthe atomic density is considerably reduced. Na_92 is the only cluster from the\ntwo considered that verifies this condition, so its thermal behavior can be\nconsidered as representative of that expected for amorphous clusters. Na_142,\non the other hand, has a discernible atomic shell structure and should be\nconsidered instead as just partially disordered. The thermal behavior of these\ntwo clusters is also compared to that of icosahedral (totally ordered) sodium\nclusters of the same sizes.",
"arxiv_id": "physics/0005045",
"authors": [
"Andr\u00e9s Aguado"
],
"categories": [
"physics.atm-clus"
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"doi": "10.1007/s100530170169",
"title": "Melting behavior of large disordered sodium clusters",
"url": "https://arxiv.org/abs/physics/0005045"
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