Ab initiostudy of quasiperiodic Bi monolayers on a tenfoldd−Al−Co−Nisurface

Abstract

We present an ab initio study of the formation of quasiperiodic Bi monolayers on the tenfold surface of a decagonal Al-Co-Ni quasicrystal. The structural model of the surface has been derived from the recently resolved structure of the $W\text{\ensuremath{-}}(\mathrm{Al}\mathrm{Co}\mathrm{Ni})$ approximant phase. As the bulk $W$ phase can be cleaved at the flat $A$ plane or the puckered $B$ plane we investigate the formation and stability of the monolayers on both surfaces. The structural model of a Bi monolayer adsorbed on the tenfold surface has been constructed on the basis of a mapping of the potential-energy landscape of an isolated Bi adatom on the substrate. We found stable quasiperiodic monolayers on both surfaces. The structure of the monolayer on the $B$ surface is less dense and more regular than that on the $A$ surface. The surface coverages are within the experimentally determined range $\ensuremath{\simeq}0.08\ifmmode\pm\else\textpm\fi{}0.02\phantom{\rule{0.3em}{0ex}}\text{atoms}∕{\mathrm{\AA{}}}^{2}$.