On “vapour---liquid” phase equilibrium in a finite system

A system of a finite number of particles (atoms, molecules) is considered under the condition N. T. V. = const. A “one drop-vapour” approximation is proposed, adapting the Mayer cluster-expansion formalism to describe the heterogeneous equilibrium state of the system. The mean cluster size distribution function obtained is compared with computer simulation results by Rao, Berne and Kalos and shows quite good agreement. The difficulties of applying the Boltzmann entropy hypothesis to the heterogenous (i.e. bistable) state of the system are discussed.