The Bi(SCN) vacancies are long-range ordered and lie within every third (010) layer of metal atoms, corresponding to a {110}-type layer in the primitive cubic BX 3 aristotype. Within these (010) planes, all the Bi(SCN) are missing, so the structure comprises two successive non-defective layers followed by a third defective layer containing only Mn metal ions [Fig. ]. This defect ordering pattern lowers the symmetry of the cubic aristotype to the orthorhombic Immm space group. When combined with the cooperative octahedral tilts produced by the bent M-SCN bonding, the structure lowers to the observed P2 1 /n space group. We confirmed that the observed framework structure is related to the parent structure within the descent-of-symmetry framework by using the ISODISTORT software package and Topas Academic