Modelling of the energetics and kinetics of Al deposition on 5-fold Al-rich quasicrystal surfaces

Abstract

We determine potential energy surfaces for the binding of Al adatoms on 5-fold AlPdMn and AlCuFe quasicrystal surfaces. Appropriate geometric models are used to select physical surface terminations. The interaction between the Al adsorbate and the substrate is described using Lennard–Jones pair-wise interactions, with parameters chosen to fit ab initio energetics for Al on relevant single crystal substrates. We identify a ‘disordered-bond-network’ (DBN) of local adsorption sites, which includes deep ‘starfish’ and ‘incomplete starfish’ ensembles. Our primary interest is in the kinetics of deposition and aggregation of Al atoms, and the possible formation of pseudomorphic starfish islands at starfish ensembles (observed for Al deposition on AlCuFe). The deposition process is modeled within the framework of a DBN lattice-gas model, wherein we specify rates for deposition and for hopping between neighboring sites of the DBN, as well as Al–Al adsorbate interactions, which stabilize islands. We, thus, present a picture for the formation of starfish islands subject to the competition between various deep sites for Al adatoms.

Acknowledgements

CG, CJJ, PAT and JWE were supported by NSF Grant CHE-0414378. DJL was supported by the Division of Chemical Sciences, USDOE–BES. The work was performed at Ames Laboratory, operated for the USDOE by ISU under contract No. W-7405-Eng-82.