VACANCY FORMATION ENERGY IN ICOSAHEDRAL STRUCTURES

A method is developed for calculating the formation energy of vacancie s that is applicable to crystalline, amorphous, and quasicrystalline s tructures. Calculations are performed in the strong-binding approximat ion for Amman-Mackey networks with different types of decorations. It is shown that the most closely packed structure, for which the formati on energy of vacancies is much less than the crystalline state, has th e smallest vacancy formation energy. This can explain the experimental data on the increased concentration of vacancies in quasicrystals com pared with crystalline objects. (C) 1998 American Institute of Physics .