621.762 Introduction. It is known that the number of possible and theoretically predicted superlattices of ordered phases is considerably larger than the number of experimentally discovered ones [1]. The main cause why many of the predicted superlattices have so far not been obtained in practice is the problem of stability of ordered phases. The present work deals with an analysis of the conditions of realization of superlattices based on the fcc lattice.During the analysis we imposed limitations, and we examined solely those binary ordered phases for whose description one or two parameters of long-range order are necessary. Such a limitation is very sensible because, firstly, binary ordered phases with three parameters of long-range order have so far not been discovered experimentally, secondly their examination greatly increases the number of possible types of superlattices which is large anyway. The size of the present article also forces us to confine ourselves to face-centered cubic densely packed lattices. The analysis of possible structures is carried out within the framework of the Ising model with rigid lattice, with interatomic pair interaction taken into account. Rigid lattice means that only concentration waves are taken into account, but not waves of atomic displacements. Long-period structures are therefore not dealt with. The analysis of the stability of superlattices was Carried out without regard to entropy, i.e., at zero temperature. These approximations are traditional.

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