Two types of columns related to decagonal quasicrystals. (a) Side view of the decagonal column. Each puckered layer contributes a decagonal ring to the decagonal column. Between the decagonal rings are small pentagons (in f1 and f3) and irregular subunits (in f2) that are alternating along the b axis. (b) Side view of the pentagonal column. The pentagonal column is constructed by pentagonal stars or pentagons that are stacked along the b axis. The centers of the decagonal columns are always occupied by the heavy Rh atoms.