The mechanism of domain-wall structure formation in Ar-Kr submonolayer films on graphite

TL;DR

This study uses Monte Carlo simulations and a simplified model to analyze how argon and krypton atoms form domain-wall structures during phase transitions on graphite, revealing how composition affects domain formation.

Contribution

It introduces a combined Monte Carlo and Frenkel-Kontorova-like model to explain domain-wall formation in Ar-Kr films on graphite, highlighting the role of argon concentration.

Findings

Transition occurs when argon covers cluster peripheries.

Incommensurate phase has domain-wall structures similar to pure krypton.

Domain composition changes with argon concentration.

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.