Geometrical properties of MDO polytypes and procedures for their derivation. I. General concept and applications to polytype families consisting of OD layers all of the same kind

The concept of MDO structures (structures of maximum degree of order) is explained in detail and defined. This concept corresponds closely to the concepts of standard, simple or regular polytypes, it seems, however, to be more adequate for complicated examples. MDO polytypes consisting of equivalent OD layers are treated in detail. For the six subcategories, simple tests showing whether a given polytype is an MDO polytype or not are given, and stepwise procedures for obtaining a complete list of all MDO polytypes of a polytypic substance are introduced. The approach is demonstrated by examples.