A structure containing a -Sn-Sn-Sn-Sb-Sb-Sb-(AAABBB) configuration along the metalsulfur chains was generated and was not found to be lower in energy, lying 4 meV/atom above the ground state. The cluster expansion for Sn 2 SbS 2 I 3 also found no lowering in energy when considering unit cells with 48 and 64 atoms. The CE correctly predicted the energy of the -Sn-Sn-Sn-Sb-Sb-Sb-configuration in a 96 atom supercell, confirming its predictive capabilities for cells larger than the training set and convergence with respect to cluster size (atomic interaction range).