Equilibrium populations of small stable clusters in nucleation theory

Small clusters containing molecules with high relative momenta are likely to decay rapidly and so such arrangements should be excluded from consideration in nucleation theory. The effect of limiting the range of the momentum integrations when calculating the partition function of clusters containing 2, 3, and 4 molecules interacting via a Lennard-Jones potential is investigated. The resulting values are larger than those calculated using the harmonic-oscillator /rigid-rotor approximation, the relative difference increasing with cluster size. However, results using parameters and experimental values representative of Argon show that internally consistent classical theory predicts the populations of these small clusters surprisingly accurately