Origin of the Formation of One- and Two-Dimensional Long Period Superlattices in Cu-Pd and Cu-Pt Systems

The origin of formation of the one- and two-dimensional long period superlattices appearing in Cu-Pd and Cu-Pt systems has been made clear, basing upon the short range interaction due to the repulsive energy of ion cores and the long range interaction produced from band electrons in the alloys. The stability conditions for the normal superlattice and the one- and two-dimensional long period superlattices were confirmed in terms of the electron number per atom, and the concentration dependence of half period for the long period superlattices was obtained. These results well explain the experimental results. Some remarks on the effects of superlattice Brillouin zone were given.