THERMALLY-INDUCED SURFACE RECONSTRUCTIONS OF MACKAY ICOSAHEDRA

Simulations of 561- and 923-atom Mackay icosahedra reveal that at ener gies below the melting point vacancies are generated in the surface la yer of the icosahedra at the vertices and edges, and that the resultin g adatoms diffuse across the surface. However, in contrast to the beha viour of smaller Mackay icosahedra, there is also a surface reconstruc tion before melting, in which the atoms of the surface layer occupy th e hexagonal close-packed sites with respect to the twenty face-centred -cubic tetrahedra which make up the Mackay icosahedron.