Assessment of the CSL and SU models for bcc-Fe grain boundaries from first principles

For some BCC STGBs, such as the Σ3{1 1 2}〈1 1 0〉, Σ3{1 1 1}〈1 1 0〉, and Σ5{3 1 0}〈1 0 0〉 GB, the CSL and SU models yield the exactly same GB structure, while for other BCC STGBs, such as the Σ5{2 1 0}〈1 0 0〉, Σ9{1 1 4}〈1 1 0〉, and Σ11{3 3 2}〈1 1 0〉 GB, the two models yield different structures, which however differ only by one vacancy. The above figure shows that a vacancy-containing CSL-model Σ5{2 1 0}〈1 0 0〉 GB (Fig. (f)) fully relaxes to the SU-model counterpart (Fig. (e)). In this case, the SU model always predicts a much lower GB formation energy than the CSL model does.91