OD approach to the polytypism in CdP 2

The structures of CdP 2 are described as stacking sequences of layers of CdP 4 tetrahedra. On the basis of the OD theory of Dornberger‐Schiff, the stacking possibilities are derived and convenient stacking notations proposed. The idealized layer structure is given, the percentage of α‐CdP 2 for any stacking sequence defined. The symbol of the OD groupoid family is P11(n)2m · (4) x, y with parameters x = y = 1/2 and (4 + ), (4 − ) as the two alternative transformations from layer to layer. The net constants are a = b ≈ 5.29 Å; the “thickness” of a layer is c 0 ≈ 4.95 Å.