13. Atomistic Simulation Techniques to Model Hydrogen Segregation and Hydrogen Embrittlement in Metallic Materials

Hydrogen embrittlement is an important phenomenon where the mechanical properties of a metallic material are degraded in the presence of hydrogen, sometimes leading to a change in the failure mode of the metallic material. Although mechanical failures due to hydrogen embrittlement have been observed for over a century, the atomic-level mechanisms associated with the hydrogen embrittlement process are still under debate. In this chapter, atomistic simulation efforts focused on hydrogen segregation and hydrogen embrittlement are reviewed. Atomistic simulation methods provide a nanoscale modeling technique capable of studying the role of hydrogen atoms on dislocation nucleation, crack propagation, and grain boundary decohesion. Examples are provided in this chapter of the use of a site-energy selection method to study hydrogen segregation and molecular dynamics simulations to study hydrogen-induced grain boundary decohesion in nickel. Grain boundary strength and work of separation in the presence of segregated hydrogen are computed from the molecular dynamics simulations. Subsequently, this data may be used in higher length scale models and simulations of the hydrogen embrittlement process.