Field Theory Analysis of Critical Behavior of a Symmetric Binary Fluid

A method is elaborated for constructing an effective field theory Hamiltonian of the Landau–Ginzburg–Wilson type for off-lattice models of binary fluids. We show that all coefficients of the effective Hamiltonian for a symmetric binary fluid can be expressed in terms of some known characteristics of the model hard-sphere fluid, namely, compressibility and its derivatives with respect to density. Application of the effective Hamiltonian is demonstrated by an example of determining the curve of critical layering points in the mean-field approximation. This curve agrees well with numerical experiment results for symmetric binary fluids.