COMPUTER-SIMULATION OF FRANK-KASPER-TYPE ICOSAHEDRAL QUASI-CRYSTALS

We have studied the atomic arrangement and the stability of the crystalline Frank- Kasper phase (AlzZnl-z)49Mg32 and of a hierarchy of rational approximants to the quasicrystalline icosahedral Al-Zn-Mg phase using numerical simulation. The model structures for the icosahedral phase have been constructed using a generalized dual method and the Henley- Elser decoration of the basic structural units. Effective interatomic interactions for the proper composition of the model have been derived from pseudopotential perturbation theory. The initial structure is subject to a molecular-dynamics annealing. We find that the crystalline and the quasi-crystalline structures are stable at room temperature, the characteristic bondorientational order is preserved on annealing. The calculated pair distribution functions show good agreement with available diffraction data of closely related icosahedral phases. © 1990 IOP Publishing Ltd.