Chemical-Reaction-Induced deformation of Body-Centered cubic iron in supercritical water leading to high risk of cleavage Fracture: A reactive Molecular dynamics study

To improve the reliability of BCC iron-based steels in supercritical water, it is crucial to understand the atomic-scale deterioration mechanisms under stress coupled with chemical reactions at the iron/water interface. Mo-lecular dynamics simulations with the reactive force field were employed to examine the atomic-scale deterio-ration mechanisms of BCC-iron and the role of chemical reactions with supercritical water. The simulation results revealed a lower yield stress and strain for BCC-iron in supercritical water than in vacuum. Yielding of the BCC-iron in both the vacuum and supercritical water occurred through the generation of partial dislocations at the surface. The deterioration of iron in supercritical water was found to originate from chemical reactions between the iron surface and water molecules; specifically, the formation of Fe-OH bonds on the iron surface due to the dissociative adsorption of water induces displacement of the surface iron atoms, accelerating the generation of partial dislocations.