Chromium concentration effect on an alloy surface stability and oxidation initiation

Abstract

Density functional theory (DFT) and tight-binding quantum chemical molecular dynamics (QCMD) have been applied to analyze the chromium concentration effect on the oxidation initiation process. The DFT calculations show that the cohesive energy is gradually decreasing with increasing chromium concentration which might reduce the surface stability. In addition, the doping of chromium on top layer of surfaces has positive segregation energies, which reveal antisegregating from the top layer. Chromium doping on the second and third layer significantly reduces the segregation energy that indicates preferential segregation. Different kinds of chromium doped Ni (111) surface and water interaction has been studied by the QCMD method. The results show that the chromium concentration noticeably lessens the oxygen depth of penetration into the structure. Thirty percent chromium doped surface is the most effective from the oxidation initiation view point. Localized chromium initiates a passivation that can protect the surface. This kind of reaction process can take place in the molecular domain of the water/alloy interface and thus play a vital role in initiating the oxidation.