Stability and mobility of tungsten clusters on tungsten (110) surface: Ab initio and atomistic simulations

L Yang and D Perez and BD Wirth, SURFACE SCIENCE, 707, 121806 (2021).

DOI: 10.1016/j.susc.2021.121806

Quantifying the surface transport properties of tungsten (W) is of prime importance to understand the formation of nano-fuzz in fusion plasma- facing conditions. The stability and mobility of W adatom clusters (W-n, n = 2-9) on the W(110) surface has been investigated by computer simulations, including ab initio calculations using density functional theory (DFT) and molecular statics (MS) simulations with multiple W interatomic potentials. The DFT results demonstrate that the sequential binding energy generally increases with number of W adatoms, except for the 5th and 7th W adatoms. The most common elemental migration steps of W-n (n>2) clusters are observed to consist of monomer and dimer hops, while larger W-n clusters can also diffuse by dissociation and recombination of smaller clusters. The threshold migration energy of W-9 is the highest, then followed by W-8, W-4, and W-6, while W-3, W-5, and W-7 have similar migration energies. Compared to DFT, each interatomic potential evaluated overestimates the binding energies of W-n clusters. The embedded-atom potential developed by Juslin and Wirth adequately predicts the threshold migration energy of W-n (n>2) clusters, although it predicts different underlying migration mechanisms. The results show that interaction mechanism between W adatoms controls the stability and mobility of W-n clusters on the W(110) surface.

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