In the MnSe4Br2 octahedra, the two Br -ions occupy equatorial cis positions around the central Mn 2+ ion with the Se 2-ions occupying the remaining four sites (S10). In contrast, in the CuSe2Cl4 octahedra the four Cl -ions occupy all equatorial positions and the two Se 2-ions are positioned trans on the axial positions. One factor that influences the magnitude of the cationic displacement in CuBiSeCl2 relative to MnBiSe2Br is the size of the ionic radii in the octahedral environment. In the MnSe4Br2 environment, all of the anionic species exhibit similar ionic radii (Br 1.96 Å, Se 1.98 Å), which causes minimal displacement of Mn 2+ . The difference in anion size in the CuSe2Cl4 octahedra is more significant (Cl 1.81 Å, Se 1.98 Å) and results in a more anisotropic displacement of Cu + . The electronegativity of the different species also plays a role in the cationic displacement; in MnBiSe2Br, Mn 2+ displaces towards the Br-Br octahedral edge since Br is more electronegative than Se (Br χr = 2.96; χr = Se: 2.55). In the CuSe2Cl4 octahedra, there is a steeper electronegativity gradient between the anionic species at the vertices (Cl χr = 3.15; χr = Se: 2.55), such that Cu + is significantly displaced in the direction of one of the Cl-Cl edges.