Examples of thus calculated flip energies are shown in Fig. for an AuPt NP with both a random compositional ordering and a locally optimal ordered structure. The flip energies readily provide an intuitive evaluation of the stability of local structural motifs. The opposite sign of the flip energies for the two elements indicates that Pt forms stronger bonds than Au. This is also reflected in the optimal atom ordering at this shape, where all Au atoms occupy undercoordinated edge sites.