A design equation for low dosage additives that accelerate nucleation

Abstract

Additives are used to control nucleation in many natural and industrial environments. However, the mechanisms by which additives inhibit or accelerate solute precipitate nucleation are not well understood. We propose an equation that predicts changes in nucleation barriers based on the adsorption properties and concentrations of trace additives. The equation shows that nucleant efficacy depends on the product of an adsorption equilibrium constant and the reduction in interfacial tension. Moreover, the two factors that determine the potency of additives are related to each other, suggesting that assays of just one property might facilitate additive design. We test the design equation for a Potts lattice gas model with surfactant-like additives in addition to solutes and solvents.

Promotion of Homogeneous Ice Nucleation by Soluble Molecules

“…The homogeneous nucleation barrier Δ G * is controlled by the ice–liquid surface tension γ, the density of ice ρ s and the difference in chemical potential between liquid and ice, Δμ = μ liquid – μ ice : Δ G * = 16πγ 3 /(3ρ s 2 Δμ 2 ). Additives that preferentially bind to the ice–liquid interface would decrease γ, thus decreasing the homogeneous nucleation barrier. − However, we find that PVA does not show preferential adsorption to the critical crystallites in the non-equilibrium nucleation trajectories (Figure b), nor in equilibrium simulations in which a hexagonal ice embryo is constrained to prevent its growth (Figure c,d). The distribution of PVA 10-mer around the ice nucleus is the same in equilibrium and non-equilibrium simulations (Supporting Information, Figure S1).…”

Induction time of a polymorphic transformation

“…Regardless of the physical mechanism, the lower surface energy of metastable phases explains the initial precipitation of metastable polymorphs during crystallization. Manipulating solution chemistry can also promote the formation of a metastable phase, as solvent or solution additives may selectively influence the surface energies of competing polymorphs, [28][29][30][31][32] which could manifest in orders of magnitude changes in their relative nucleation rates.…”

Molecular properties of interfaces relevant for clathrate hydrate agglomeration

“…Understanding nucleation could lead to new KHIs. Poon et al [37] e.g., suggested design principles starting from the classic nucleation theory. Recent nucleation studies couple order parameters, defined using short-ranged correlations among molecules, with enhanced sampling techniques, e.g., metadynamics, to observe the rare events leading to nucleation.…”