as is often found for K + and NH This structure is a ( √ 2 × √ 2 × 2) supercell of the hypothetical primitive cubic Pm 3m aristotype AM(NCS) 3 , and its structure derives from this Pm 3m structure (using the setting with the A-site at the origin) through four symmetry-lowering distortions. The M-site cations have rocksalt order and this order transforms as the R - 2 irreducible representation (irrep). The A-site cations have columnar order (transforming as the M + 1 irrep), and there is no evidence of site-mixing from single-crystal diffraction. The presence of simultaneous A-and M-site occupational order means that 1 and 2 are double double vacancy-ordered perovskites, 2ANiBi(SCN) 6 . 1 and 2 possess the common a -a -c + (Glazer) or GdFeO 3 octahedral tilt sequence (which transforms as a combination of the R -