Evidence for a size-dependent transition between noncrystalline structures and crystalline structures with defects in frozen Lennard-Jones clusters

Liquid Lennard-Jones clusters of 14 different sizes from N=55-923 atoms were cooled down in Monte Carlo simulations (40 runs for each size) to the reduced temperature T*=0.05. Structural analysis and visualization were applied for classification of the internal structure of all 560 final clusters. Small clusters revealed the presence of the multishell icosahedra or regular polyicosahedra. In larger clusters, beginning from N = 309, the noncrystalline atom ordering is often replaced by the formation of defected crystalline clusters in the form of layered face-centered cubic-hexagonal close-packed (fcc-hcp) clusters or defected layered clusters with some additional nonparallel hcp overlayers. The presence of regular polyicosahedral clusters, relatively numerous even at the largest analyzed sizes, is attributed to kinetic effects in structure formation.