Fig. 8. Mono-vacancy in bcc Fe represented in the descriptor space.

The 127-atom cell is represented based on the bispectrum SO(4) with R_c = 4.0 Å and $j_{\max }=3.5$ resulting in 26 descriptor components. a Heatmap of the bispectrum components. The lines deviating from the rest of the map correspond to the atomic environments impacted by the mono-vacancy. b Representation of the atomic array based on the first descriptor component. The atoms are coloured according to the first column, indicated with an arrow in a. Purple atoms correspond to the first coordination sphere of the vacancy, blue corresponds to the second and green corresponds to the third.