Molecular dynamics study of neutral and multiply charged sodium clusters

On the premelting features in sodium clusters

Melting in Na(n) clusters described with an empirical embedded-atom potential has been reexamined in the size range 55</=n</=147 with a special attention at sizes close to 130. Contrary to previous findings, premelting effects are also present at such medium sizes, and they turn out to be even stronger than the melting process itself for Na(133) or Na(135). These results indicate that the empirical potential is qualitatively inadequate to model sodium clusters.

Charge-induced fragmentation of sodium clusters

The fission of highly charged sodium clusters with fissilities X>1 is studied by ab initio molecular dynamics. Na4+24 is found to undergo predominantly sequential Na+3 emission on a time scale of 1 ps, while Na(Q+)(24) ( 5< or =Q< or =8) undergoes multifragmentation on a time scale > or =0.1 ps, with Na+ increasingly the dominant fragment as Q increases. All singly charged fragments Na(+)(n) up to size n = 6 are observed. The observed fragment spectrum is, within statistical error, independent of the temperature T of the parent cluster for T< or =1500 K. These findings are consistent with and explain recent trends observed experimentally.