Chemical potential of iron in systems of low dimensionality

Abstract The influence of particle size on heterogeneous equilibria is investigated using Fe clusters as an example. Considering a thermodynamic cycle, the change in free enthalpy for the transfer of an Fe atom from a dispersed system to the bulk is analyzed with the aid of experimental data from molecular beam experiments. Dissociation energies of mass-selected clusters are used for this purpose. It is shown that predictions within the framework of equilibrium thermodynamics, considering the free surface, are quantitatively correct for nanoscale clusters with less than 100 atoms. The effects on the redox behavior as well as the dependence of the work function on the cluster size are also addressed and discussed. In comparison with quantum chemical studies based on density functional theory, the simple thermodynamic model is surprisingly robust in predicting the chemical behavior of Fe in systems with reduced dimensionality.