Atomistic simulations of nanoscale tungsten clusters: From structure and energetics to melting properties

Abstract

Tungsten (W) dust generated from the interactions between the energetic edge plasma and W-based first-wall materials in future nuclear fusion reactors can significantly affect the plasma stability. As the precursor of dust, nanoscale clusters could aggregate and grow to become dust and are essential to the understanding of dust formation. Here, atomistic simulations have been used to explore the structure, energetics and melting properties of nanoscale W clusters. Comparisons of cluster configurations determined by two methods (high-temperature simulated annealing of a random configuration and low-temperature simulated annealing of a body-centered cubic configuration) reveal that the former technique gives more stable configurations for small clusters (N<77), while the latter method yields energetically more favorable configurations for large ones (N⩾77). Magic numbers corresponding to icosahedral, polyicosahedral and bcc structures are found. We further show that the melting points (Tm) of the clusters follow a well-established power-law correlation with the number of atoms (N) in the clusters, scaling as Tm∝(N/2)−1/3. This study will provide useful reference for the ongoing investigation of dust properties.