Interatomic potential and the structure of rare gas clusters

The relationship between the structure and the interatomic potential of rare gas clusters, especially the stability of the Mackay icosahedron to the variation of the interatomic potential has been studied. By molecular dynamics simulation, the structure and the energy of magic number clusters of 13 and 55 atoms were calculated for three types of the model potential, the Lennard-Jones, the Born-Mayer, and the Morse type, each of which contains one variable parameter. The Mackay icosahedron is stable to the variation of potentials within moderate well-width. However, for hard potentials the hcp unit cell of the 13 atoms cluster or the cuboctahedron of the 55 atoms cluster is more stable than the Mackay icosahedron. The onset of the structural transition from the icosahedron to the ccp cuboctahedron or eventually to the hcp unit cell to the variation from moderate to hard potentials occurs earlier for the 55 atoms cluster. This result leads to the expectation that for clusters of big size the transition may occur even for moderate potentials. For soft potentials a spherical structure like a liquid droplet of the 55 atoms cluster is more stable than the Mackay icosahedron or the ccp cuboctahedron.