Nucleation at larger supersaturations

Abstract

In 1962, Lothe and Pound[4] modified the classical theory of homogeneous nucleation of Becker and Doring[3] by introducing free energy contributions which affected the predictions of nucleation rates and, consequently, the critical supersaturations required for the onset of condensation. As an approximation, Lothe and Pound added their energy contributions only to the classical formation energy of a critical nucleus. When the energy contributions are considered more rigorously for clusters of any size, the Lothe-Pound theory differs remarkably from its earlier approximations at larger supersaturations. Spontaneous condensation without nucleation is expected to occur at some critical large supersaturation. The condition for the onset of spontaneous condensation can be expressed in terms of a dimensionless energy parameter, γ, which also determines the nucleation rates. For a number of published condensation experiments, γ has been calculated. The evaluation reveals that the Lothe-Pound contributions can be justifiably neglected only in a few cases. In some other cases, spontaneous condensation is expected to occur.