Relaxation of Mackay icosahedra

Multilayer icosahedra, first introduced about twenty years ago by Mackay [Acta Cryst. (1962), 15, 916-918], are no longer considered a geometrical curiosity, as small icosahedral particles have been observed in a great number of experiments. The hard-sphere models, previously considered, are not really suited to the study of physical properties because they fail to express the important stresses due to the icosahedral structure. Therefore, Mackay icosahedra, made of atoms interacting through a Lennard-Jones potential, were constructed and allowed to relax freely. Results of the calculation are given, consisting of a detailed description of relaxed icosahedra with up to nine layers, i.e. with up to almost 3000 atoms.