Analytical description of the short-range order in alloys with many-body atomic interactions. II

The recently elaborated approach (Chepulskii R V and Bugaev V N 1998 J. Phys.: Condens. Matter 10 7309-26, 7327-48) based on the joint application of the thermodynamic fluctuation method and perturbation theory is generalized to the case of the presence of not only pair but also nonpair atomic interactions of arbitrary orders in an alloy. Within such an approach, a number of new analytical approximations are derived for calculation of the grand thermodynamic potential as well as of the short-range order parameters and their Fourier transform in disordered binary alloys of arbitrary compositions and with Bravais crystal lattices. The effective radius of atomic interactions is not limited a priori. The inverse effective number of atoms interacting with one fixed atom as well as the inverse temperature are successively used as a small parameter of expansion. The developed approach may be also followed in studies of magnetics in the framework of the Ising model and of fluids and amorphous materials within the lattice gas model as well as in investigations of low-dimensional lattice systems.