The energetics of large Lennard-Jones clusters: transition to the hexagonal close-packed structure

The energetics of large multiply twined particles (MTPs) such as decahedra with fivefold symmetry, face-centred cubic (fcc) and hexagonal close-packed (hcp) clusters in size from 2000 to ~45000 atoms was numerically analysed. Clusters were relaxed freely under the Lennard-Jones pair potential to the energy minimum. The essential extension of size compared to previous studies and the additional shape-optimisation of hcp and fcc clusters as well as truncated decahedra appears to be of high importance in the potential energy analysis. The best-optimised decahedra were confirmed to be the most favourable structure from 2000 to ~105 atoms. Only in the short size interval, above N ∼10000 atoms, the best-optimised fcc clusters and simplest Marks' decahedra could alternate, while above N ∼14000 atoms does the shape-optimised hcp structure be proved to become more favourable for single crystal particles compared to the best-optimised fcc structure. Depending on shapes and sizes, decahedra and hcp clusters can alternate in the wide size interval above N ∼ 14000 atoms and presumably form the mixed abundances of clusters belonging to the both symmetries. Finally, the upper limit for stable MTPs was estimated to be about N ∼105 atoms, while above only the hcp clusters are the most favourable.