PAIR VERSUS MANY-BODY POTENTIALS IN ATOMIC EMISSION PROCESSES FROM A CU SURFACE

Atom emission from the (100) surface of a Cu crystal is investigated using molecular dynamics simulation. Different potentials are employed: the Morse potential as an example of pair potentials, and many-body potentials of the EAM and the tight-binding type. Many-body potentials lead to a slightly smaller surface binding energy than pair potentials, when fitted to the same cohesive energy of the bulk crystal. Furthermore, many-body potentials lead to a stronger refraction of emitted atoms away from the surface normal. As a consequence, the maximum in the energy distribution of emitted particles is shifted to around 50% higher energies for many-body potentials, if compared to the prediction of the model of a planar surface barrier. These characteristic deviations between pair and many-body potentials are explained by using simple analytical reasoning.