Cubic and Related Structures

The antiperovskite or inverse perovskite structure is adopted by many compounds with an overall composition AjBX, where A and B are metals and X is typically C, N, O and B. There are two broad categories. The first, not described here, are essentially alloys containing interstitial nonmetal atoms in octahedral interstices typical examples being Mn N, derived from the face-centred cubic stmcture of Mn, and FCjPtN, derived from the alloy FejPt, with the CUjAu structure. 

CuNMUji cubic a=0.3907nm, Z= 1 Space group, Pm3m (No. 221)  

The Mn atoms lie at the corners of the unit cell. The N atoms lie at the cell centre and are surrounded by a regular octahedron of Cu atoms. 

The nitride antiperovskites show other structures, analogous to those displayed by oxide perovskites, but the number of known examples of these phases is minimal to date. The phases PNCaj and AsNCaj have tilted octahedra and belong to the GdFeOj structure type, tilt system a b b . AsNCr is tetragonal with tilt system aVc . 

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