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Formation, atomic distribution and mixing energy in two-dimensional PdxAg1-x surface alloys on Pd(111)

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<mark>Journal publication date</mark>14/08/2012
<mark>Journal</mark>Physical Chemistry Chemical Physics
Issue number30
Volume14
Number of pages8
Pages (from-to)10754-10761
Publication StatusPublished
<mark>Original language</mark>English

Abstract

The formation and atom distribution in two-dimensional PdxAg1-x/Pd(111) monolayer surface alloys were studied by high resolution scanning tunnelling microscopy (STM) with chemical contrast. From short-range order (SRO) parameters, we calculate preferences for like or unlike nearest neighbours to elucidate the mixing behaviour of the two components for various sub monolayer Ag surface contents. In the regime of low Ag surface contents (60% Ag) result in a disperse distribution of the atoms in the surface. Effective pair interactions (EPIs) were derived by comparing the measured distribution with distributions obtained using Monte Carlo (MC) simulations. From the EPIs, we derived a function for the mixing energy, which can describe the change from clustering to a disperse distribution. The effects of the resulting surface atom distributions and of the Ag coverage dependent surface mixing/demixing on catalytic reactions are discussed.