Spin-fluid approach in the theory of a classical fluid

The simplest model of a two-dimensional fluid is proposed. It is based on the frustrated Heisenberg model that allows qualitative description of the behavior of a pair correlation function for different forms of a two-step potential $U(r)$. The tendency toward the formation of a quasi-bound state is demonstrated for a potential with a local minimum at its repulsive part. It is shown that the fluid can undergo a phase transition upon changing temperature in the case of the two-step potential.