Computational study of sputtering of tungsten-based refractory high-entropy alloys

Sputtering is a detrimental phenomenon needed to be considered during the development of nuclear fusion reactors. The materials facing the plasma must withstand high temperatures and high magnetic fields, and endure various forms of damage and progressive changes resulting from the high-dose irradiation conditions. Sputtering of the surfaces will affect material properties, introduce contamination into the plasma, and change the surface of materials. Therefore, it is crucial to understand which and how many particles are sputtered and their properties. In this study, tungsten and tungsten-based medium/high-entropy alloys (NbVW and MoTaNbVW) are studied using molecular dynamics simulations under various conditions. The results show that both alloys, in most conditions, sputter more than W across different energies, surfaces, and angles. However, lighter elements, such as vanadium and niobium, have higher sputtering yields than heavier elements until a steady state is reached, at which point all elements sputter at the same rate. This preferential sputtering of lighter elements can be a pro in fusion reactors, as impurities will cool the plasma through radiative loss and lighter species with fewer electrons will remove less energy from the plasma. The surfaces were depleted of the lighter elements after continuous irradiation and, therefore, showed an enrichment of heavier atoms such as tungsten and tantalum.