Oxidation of Tungsten at Room Temperature Irradiated by Oxygen Plasma

The performance of tungsten as a fusion material depends on its surface properties, which are strongly affected by the interaction with impurities, either already contained in the bulk or coming from the plasma. Plasma-facing components, such as the divertor and the first wall of the current fusion reactors, as well as many of the laboratory experiments, are operating at or are cooled down to room temperatures. We performed a detailed molecular dynamics study of the processes of oxidation of a tungsten surface at 300 K when it was cumulatively irradiated by a low-energy oxygen plasma. We developed and used a ReaxFF W-O-H classical potential, capable of treating reactive interactions of all atoms in the system, including polar interactions present when O interacts with tungsten. We also studied the properties of the oxidized layers and their response in the form of reflection, retention, and chemical sputtering to the impact of oxygen.