On the Ground State Structure of Adsorbed Monolayers: Can One Find them by Monte Carlo Simulation?

Abstract

While the classical ground state structure of an atomic monolayer adsorbed at a noncorrugated perfectly flat substrate trivially is a triangular lattice, the spacing being the minimum of the interatomic potential, nontrivial structures occur on corrugated substrates. This problem is exemplified for the (100) face of a face-centered cubic crystal, varying both the density of the adsorbed monolayer and the strength of the potential due to the surface. Increasing the density beyond that of the commensurate c(2 x 2) structure, incommensurate patterns become stable with “heavy” walls (HW) oriented along the face diagonals [including the “crossing heavy walls” (CRHW) phase]. It is shown that slow cooling Monte Carlo simulations end up by frozen-in metastable irregular domain patterns, however. States with lower energy can be found by relaxation of suitably chosen regular domain patterns.