Kinetic control of competing nuclei in a dimer lattice-gas model

TL;DR

This paper introduces a lattice-gas model with two dimer types to study complex nucleation pathways involving competition between stable and metastable phases, revealing how mobility influences nucleation outcomes.

Contribution

The study develops a two-dimer lattice-gas model that captures competing nucleation pathways and uses Forward-Flux Sampling to analyze how mobility affects phase selection.

Findings

Nucleation probabilities depend on dimer mobility.

Multiple pathways include direct nucleation and metastable phase domination.

Stable phase can nucleate after metastable nuclei appear.

Abstract

Nucleation is a key step in the synthesis of new material from solution. Well-established lattice-gas models can be used to gain insight into the basic physics of nucleation pathways involving a single nucleus type. In many situations a solution is supersaturated with respect to more than one precipitating phase. This can generate a population both stable and metastable nuclei on similar timescales and hence complex nucleation pathways involving competition between the two. In this study we introduce a lattice-gas model based on two types of interacting dimer representing particles in solution. Each type of dimer nucleates to a specific space-filling structure. Our model is tuned such that stable and metastable phases nucleate on a similar timescale. Either structure may nucleate first, with probability sensitive to dimer mobility. We calculate these nucleation rates via Forward-Flux Sampling and demonstrate how the resulting data can be used to infer the nucleation outcome and pathway. Possibilities include direct nucleation of the stable phase, domination of long-lived metastable crystallites, and pathways in which the stable phase nucleates only after multiple post-critical nuclei of the metastable phase have appeared.