Structures and Topological Transitions of Hydrocarbon Films on Quasicrystalline Surfaces

Lubricants can affect quasicrystalline coating surfaces by modifying the commensurability of the interfaces. We report results of the first computer simulation studies of physically adsorbed hydrocarbons on a quasicrystalline surface: methane, propane, and benzene on decagonal Al-Ni-Co. The grand canonical Monte Carlo method is employed, using novel embedded-atom method potentials generated from ab initio calculations, and standard hydrocarbon interactions. The resulting adsorption isotherms and calculated structures show the films' evolution from submonolayer to condensation. We discover the presence and absence of the fivefold to sixfold topological transition, for benzene and methane, respectively, in agreement with a previously formulated phenomenological rule based on adsorbate-substrate size mismatch.