Iron sulfide films
are present in many applications, including
lubricated interfaces where protective films are formed through the
reactions of lubricant additive molecules with steel surfaces during
operation. Such films are critical to the efficiency and useful lifetime
of moving components. However, the mechanisms by which films form
are still poorly understood because the reactions occur between two
surfaces and so cannot be directly probed experimentally. To address
this, we explore the thermal contribution to film formation of di-tert-butyl disulfidean important extreme pressure
additiveon an Fe(100) surface using reactive molecular dynamics
simulations, where the reactive potential parameters are validated
by comparison to ab initio calculations. The reaction pathway leading
to the formation of iron sulfide surfaces is characterized using
the reactive simulations. Then, the film formation process is mimicked
by simulations where di-tert-butyl disulfide molecules
are cyclically added to the surface and subjected to temperatures
comparable to those expected due to frictional heating. The use of
a reactive empirical potential is a novel approach to modeling the
iterative nature of thermal film growth with realistic lubricant additive
molecules.