Effect of substrate relaxation on adsorption energies: The example of α-Fe_2O_3(0001) and Fe_3O_4(111)

摘要

Adsorption energies calculated from total energy differences of the adsorbate-substrate and isolated adsorbate and substrate systems consist of chemical contribution which results from the electron charge redistribution, and mechanical (relaxation) energy component resulting from the changes in the atomic configuration of the adsorbate-substrate system during adsorption. In this work Au and CO adsorption on theα-Fe2O3(0001) and Fe3O4(111) surfaces is used as model systems for the separation of these two contributions by critical analysis of published data and additional density functional theory calculations in order to analyze how the calculated adsorption energies are influenced by substrate relaxation effects. It is shown that a reliable estimation of these effects is obtained from the difference between desorption and adsorption energies. The scatter in the calculated adsorption energies of Au and CO on iron oxides is explained.