Carbon adsorption on and diffusion through the Fe(110) surface and in bulk: Developing a new strategy for the use of empirical potentials in complex material set-ups

Oil and gas infrastructures are submitted to extreme conditions
and off-shore rigs and petrochemical installations require
expensive high-quality materials to limit damaging failures.
Yet, due to a lack of microscopic understanding, most of these
materials are developed and selected based on empirical
evidence leading to over-qualified infrastructures. Computational
efforts are necessary, therefore, to identify the link
between atomistic and macroscopic scales and support the
development of better targeted materials for this and other
energy industry. As a first step towards understanding
carburization and metal dusting, we assess the capabilities of
an embedded atom method (EAM) empirical force field as well
as those of a ReaxFF force field using two different parameter
sets to describe carbon diffusion at the surface of Fe, comparing
the adsorption and diffusion of carbon into the 110 surface and
in bulk of a-iron with equivalent results produced by density
functional theory (DFT). The EAM potential has been
previously used successfully for bulk Fe-C systems. Our study
indicates that preference for C adsorption site, the surface to
subsurface diffusion of C atoms and their migration paths over
the 110 surface are in good agreement with DFT. The ReaxFF
potential is more suited for simulating the hydrocarbon reaction
at the surface while the subsequent diffusion to subsurface and
bulk is better captured with the EAM potential. This result
opens the door to a new approach for using empirical potentials
in the study of complex material set-ups