Island formation during Al deposition on 5-fold Al-Cu-Fe quasicrystalline surfaces: Kinetic Monte Carlo simulation of a disordered-bond-network lattice-gas model

Scanning tunneling microscopy experiments have previously revealed the formation of pseudomorphic starfish-shaped islands during the initial stages of Al deposition on 5-fold icosohedral Al-Cu-Fe quasicrystal surfaces. To simulate this process, we first identify appropriate 5-fold surface terminations of Al-Cu-Fe from a model for bulk structure, and construct associated potential energy surfaces for the binding of Al adatoms on these terminations. We then identify a 'disordered-bond-network' (DBN) connecting neighboring local adsorption sites for Al on Al-Cu-Fe, and determine site binding energies as well as activation barriers for Al adatom hopping between neighboring sites. Al-Al adsorbate interactions, which stabilize islands, are also prescribed. Then, within the framework of a DBN lattice-gas model, we simulate the deposition and diffusion of Al on Al-Cu-Fe. We explore the competition between starfish and incomplete starfish ensembles of sites (which provide traps in the form of deep potential energy wells for diffusing Al) and isolated trap sites, with regard to the heterogeneous nucleation and aggregation of Al into islands.