Abstract
Using Monte Carlo simulation method in the canonical ensemble, we have studied the commensurate-incommensurate transition in two-dimensional finite mixed clusters of Ar and Kr adsorbed on graphite basal plane at low temperatures. It has been demonstrated that the transition occurs when the argon concentration exceeds the value needed to cover the peripheries of the cluster. The incommensurate phase exhibits a similar domain-wall structure as observed in pure krypton films at the densities exceeding the density of a perfect $(\sqrt{3}\times\sqrt{3})R30^\circ$ commensurate phase, but the size of commensurate domains does not change much with the cluster size. When the argon concentration increases, the composition of domain walls changes while the commensurate domains are made of pure krypton. We have constructed a simple one-dimensional Frenkel-Kontorova-like model that yields the results being in a good qualitative agreement with the Monte Carlo results obtained for two-dimensional systems.
Highlights
We studied semi-infinite systems consisting of the rectangular commensurate domain of the size Lx × Ly with periodic boundary conditions applied along the x and y -axes, but with free interfaces running along the y -axis
Using Monte Carlo simulation method we studied the C-IC transition which occurs at low temperatures in finite clusters of Kr atoms contaminated with argon
As soon as the argon concentration becomes higher than this threshold value, the system undergoes the C-IC transition leading to the formation of the domain-wall structure
Summary
The commensurate-incommensurate (C-IC) transitions in adsorbed films have been experimentally observed in a variety of systems [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] and studied by theoretical methods [16,17,18,19,20,21,22,23,24,25,26,27] and computer simulations [28,29,30,31,32,33,34,35,36,37]. The C-IC transition in one-component finite clusters of Lennard-Jones atoms adsorbed on graphite has been studied by Houlrik et al [37] They have used Monte Carlo method to study the effects of the corrugation potential on the structure of finite systems and have shown that for a given amplitude of the corrugation potential the presence of free surfaces enhanced the stability of the C structure. In this paper we study the mechanism of the C-IC transition of submonolayer mixed films made of argon and krypton using Monte Carlo simulation methods and appropriately modified one-dimensional (1D) Frenkel-Kontorova (FK) model [52, 53].
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