Surface relaxation and initial surface corrosion of strained Mo(100) surface

Metal surface corrosion is a common phenomenon under atmospheric conditions, however, the design of corrosion resistant materials at the atomistic level is hindered by the limited knowledge about the corrosion mechanism. Here, the initial surface corrosion of metallic molybdenum, an important in industrial materials, is investigated by using the density functional theory calculations. The adsorption energies of several key corrosion intermediates on Mo(100) surfaces are calculated under various strain (-5% to 5%). The concerted effect of strain and adsorbates can cause significant relaxation of surface atoms (the in-plane atom displacement is within 0.1 - 0.4 Å). The small repulsive lateral interactions among O* adsorbates allow high O coverages. The ensuing corrosion follows the uniform corrosion process rather than the pitting corrosion process. Tensile strain can accelerate the initial surface corrosion process. Further analyses indicate that higher coverage of adsorbates correlates to bigger variation of the interlayer distances, which is the consequence of the competition between the adsorption interactions and the interlayer interactions. The findings reveal the oxidation process over Mo(100) and provide a general understanding for metal corrosion.