Title: THE ORDER PARAMETER IN BINARY MIXTURES
Authors: O.V.Patsahan (Institute for Condensed Matter Physics, of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 290011 Lviv, Ukraine)

Phase transitions in a binary mixture are investigated by means of the collective variables method with a reference system. It is shown that the system is described with two sets of collective variables: $\eta_{\vec k}$ and $\xi_{\vec k}$. The CV connected with the order parameter is $\eta_{\vec k=0}$ in the case of the gas-liquid critical point as well as in the case of the mixing-demixing phase transition. The particular form of $\eta_{0}$ for each of these phenomena can be determined by means of the relations between the microscopic parameters,temperature, density and concentration of the system under consideration.

Comments: Figs. 1, Refs. 10, Tabs. 0.