An Atomistic Study of Oxidation Initiation on Different Kinds of Fcc Fe-Cr Binary Alloy Surfaces

摘要

Quantum chemical molecular dynamics (QCMD) method has been applied to study water molecules adsorption and dissociation phenomena on fcc Fe-Cr(111), Fe-Cr(110) and Fe-Cr(100) binary alloy surfaces at 288℃. The water molecules adsorbed via oxygen atom on top site of the surfaces and the bond distances are varies from 2.30 to 2.60 A. The diffusivity of oxygen of Fe-Cr(111) surface is the highest among all the surfaces. Chromium-oxygen preferential bond formation has occurred during the reaction process. Mulliken population analysis has also been performed to understand the bond mechanism. Chromium atoms acquired highly positive in charge that can form strong bond with negatively charged oxygen. Consequently, the bonding decelerates the oxygen diffusivity into surfaces. Deeply diffused hydrogen has negatively charged. Interstitially trapped hydrogen can be able to lessen strength of metallic bond. Thus, the process may accelerate the early stage of oxidation process.