  Recently, we clarify connection of spatial constraint and equilibrium
macroscopic properties in disordered states of classical system under the fixed
composition; namely few special microscopic states, independent of constituent
elements, can describe macroscopic properties. In this study, we extend our
developed approach to composition-unfixed system. Through this extension in
binary system, we discover a single special microscopic state to determine not
only composition but also Helmholtz free energy measured from unary system,
which has not been described by a single state.
