American Club Sandwich
In search of a polytype next nearest neighbour classification scheme
In assembling the database on polytype neighbours from the topographic survey a taxonomy has been developed to accommodate the commonly encountered edge profiles. Crystals frequently display a pattern of coalescence that has been described as an American club sandwich to indicate the complex nature of the relationships between the common polytypes 6H, 15R and 4H with layers of one-dimensional disorder and long period polytypes.
In the case shown here morphological clues can help to build a polytype model. 6H+4H+6H+1DD+6H+1DD+6H+1DD+15R