First-principles study on field evaporation of surface atoms from W(011) and Mo(011) surfaces

The simulations of field-evaporation processes for surface atoms on W(011) and Mo(011) surfaces are implemented using first-principles calculations based on the real-space finite-difference method. The threshold values of the external electric field for evaporation of the surface atoms, which are ∼ 6 V/Å for tungsten and ∼ 5 V/Å for molybdenum, are in agreement with the experimental results. Whereas field evaporation has been believed to occur as a result of significant local-field enhancement around the evaporating atoms, in this study, the enhancement is not observed around the atoms but above them and the strength of the local field is much smaller than that expected on the basis of the classical model.