Lattice Modulation in the Long Period Ordered Alloys Studied by X-Ray Diffraction. III. Cu3Pd(α'')

Periodic atom displacements in the long period ordered alloy Cu 3 Pd(α'') with the one-dimensional anti-phase domain structure have been investigated by X-ray diffraction using an alloy single crystal. It has resulted from the crystal structure analysis, that in Cu 3 Pd(α'') the heavier atoms (palladium) are displaced toward the anti-phase boundary and the lighter atoms (copper) away from it, giving rise to puckered planes. These behaviors are different from those of Au 3 Cd and CuAuII in which the heavier atoms are displaced away from the boundary and the lighter atoms toward it. Thus, the atom displacements are affected by the kind of alloys. A little disordering is present in atomic sites in the mixed plane facing the boundary.