W-concentration dependent radiation-induced amorphization in M23C6 via atomic-scale analysis by Voronoi tessellation

Voronoi tessellation was innovatively applied to interpret the high-resolution atomic-scale micrographs of the Cr-W-C ternary M₂₃C₆ with and without irradiation to provide mechanistic insight into the phase stability under irradiation. A W concentration-dependent radiation-induced amorphization behavior was observed and the amorphization was confirmed in the 4 W sample (∼12 at.%W). Analysis of the local crystal structure using Voronoi diagrams shows that the average size of each Voronoi cell and its standard deviation are affected by irradiation and W concentration. In addition, the standard deviation of the Voronoi cell size, which is considered an indicator of the uncertainty of the atomic column positions, is also plotted as a function of the lattice parameter change. This mathematical analysis indicates that a higher W concentration tends to cause a more severe disordering of the atomic distribution upon irradiation, which is directly correlated with the occurrence of amorphization.