抄録
The author found only one symmetry plane (1\bar210) in the superlattice of the ε-phase of Cu–Sb alloy, where an ideal distribution of 8 Sb atoms was assumed in the unit cell. This symmetry plane coincides with the plane of shear and is normal to the twinning plane (10\bar11), of the twin which was predicted in a hexagonal lattice with the axial ratio, 0.7947, in a previous paper. Thus, the author assumed the (10\bar11) twin in the ε-phase, and discussed atom movements in the twinning. The possibility of detectable twins of this type seems so small that it may be 1/6 (or less) of the possibility for the {10\bar12} twin in common h.c.p. metals.
R. W. Cahn has confirmed that no twin can form in an ordered Fe3Al crystal. Based on this, the author assumed some geometrical requisitions for the twinning of superlattices.
