'The crystal structure problem' in noble gas nanoclusters

Calculations of the energetics of multiply twinned particles (MTPs) such as icosahedra and decahedra with fivefold symmetry as well as face-centered cubic (fcc) and hexagonal close-packed (hcp) particles in the size interval from 13 up to similar to 45,000 atoms were made applying Lennard-Jones potentials. We essentially extended the size interval comparatively with previous studies and included shape-optimized hcp clusters in the global energy analysis that gives rise to the new insight into the basic fcc/hcp problem. For the cluster size N from minimal up to N similar to 2000 atoms the binding energy is highest for icosahedra, in the size interval from 2000 up to similar to 11,500 atoms decahedra prevail, above N similar to 11,500 atoms decahedra and optimized fee clusters were found to alternate. The hcp structure was revealed to become favorable above N similar to 34,000 atoms. Thus, hep clusters can attain their preference with respect to MTPs (comprising fee fragments) and optimized fee clusters only for very large sizes. The comparison with several other models is suggested and the opportunity of experimental observations is discussed. (c) 2006 Elsevier B.V. All rights reserved.