  The behavior of hydrogen in iron and iron alloys is of interest in many
fields of physics and materials science. To enable large-scale molecular
dynamics simulations of systems with Fe-H interactions, we develop, based on
density-functional theory calculations, an interatomic Fe-H potential in the
Tersoff-Brenner formalism. The obtained analytical potential is suitable for
simulations of H in bulk Fe as well as for modeling small FeH molecules, and it
can be directly combined with our previously constructed potential for the
stainless steel Fe-Cr-C system. This will allow simulations of, e.g.,
hydrocarbon molecule chemistry on steel surfaces. In the current work, we apply
the potential to simulating hydrogen-induced embrittlement in monocrystalline
bulk Fe and in an Fe bicrystal with a grain boundary. In both cases, hydrogen
is found to soften the material.
