Surface relaxation of α-iron and the embedded-atom method

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Abstract
The surface-relaxation properties of bcc iron are calculated with the embedded-atom method (EAM). The main goal of the investigation is to determine what constraints the correct prediction of surface-relaxation quantities places on features of EAM potentials. Seven specific EAM potentials are designed to reproduce experimental bulk properties including elastic constants and phonon frequencies. The features of the embedding function F(ρ) and two-body potential V(r) for each potential are discussed. The perpendicular and parallel surface relaxation quantities for the six faces (100), (110), (111), (210), (310), and (211) are calculated for each potential. The theoretical predictions are compared with the experimental data. Two of the models are found to reproduce the experimental data rather well. The influence of the features of each potential on the atomic spacing is discussed. Our main conclusion is that surface-relaxation predictions can place important constraints on the EAM. In the case of bcc iron, important roles of nearest-neighbor repulsion and second-neighbor attraction are indicated by the experimental surface-relaxation data.