Calculation of the Coverage

A very important feature to be taken into account when comparing the results of a simulation with experiments is the quality of the interatomic potentials used to perform the simulations. In this work, the embedded-atom method (EAM) is used, because it is able to reproduce important characteristics of the metallic binding, such as the equilibrium lattice constants and heats of solution of the binary alloys. 

The EAM considers that the total energy (7tot of an arrangement of N particles may be calculated as the sum of energies Ui, corresponding to individual particles, that is, 

Fi is the embedding function and represents the energy necessary to embed an atom i in the electronic density pnj, at the site where this atom is located. ph,i is calculated as the superposition of the individual electronic densities Piiry)  

the attractive contribution to the embedded-atom potential is given by the embedding energy, which accounts for many-body 

On the other hand, the repulsion between ion cores is represented through a pair potential Vijiry), which only depends on the distance between the cores r j  

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The absolute determination of coverage is much more difficult. The formalism is well known, i.e., it is possible to go from the intensity of a spectral ion to the concentration material on the surface, but this can only be worked out if the transition dipole moment is known. A very rough order of magnitude version of this can, however, usually be obtained by analogy (rather than by quantum mechanical calculation) so that somewhat better than an order of magnitude calculation of the coverage of the surface radicals can be given. 

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