Structures and rearrangements of LiCl clusters.

Molecular dynamics simulations are used to investigate the low-temperature structures and temperature-driven rearrangements of (LiCl)n clusters, with n ranging from 3 to 500. It is found that for n < or = 32 expanded, ring-based structures are energetically more stable than cubic (rocksalt) forms at low temperature. For n > or = 108, the cubic structures are lower in energy, but as the clusters are heated rearrangements to expanded structures occur well below the melting temperature. Hexagonal (LiCl)3 rings are a distinguishing feature of the expanded, ring-based structures. Highly asymmetric ion sizes are essential for the formation of the expanded structures. Similar transitions from more-ordered to less-ordered solid states are not found for corresponding (KCl)n clusters, which remain in the cubic structure until they melt.