Amorphous Precursors of Crystallization during Spinodal Decomposition

TL;DR

This paper investigates the formation of amorphous precursors during spinodal decomposition, revealing how early-stage length scale selectivity leads to icosahedral order and subsequent crystalline nucleation, influenced by quench depth.

Contribution

It introduces a Landau free energy model to describe the dynamics of crystallization and amorphous precursor formation during spinodal decomposition.

Findings

Precursors exhibit icosahedral order during early SD stages.

Crystalline bcc nucleates heterogeneously on amorphous clusters.

Quench depth significantly affects the structure and phase volume fraction.

Abstract

A general Landau's free energy functional is used to study the dynamics of crystallization during liquid-solid Spinodal Decomposition (SD). The strong length scale selectivity imposed during the early stage of SD induces the appearance of small precursors for crystallization with icosahedral order. These precursors grow in densely packed clusters of tetrahedra through the addition of new particles. As the average size of the amorphous nuclei becomes large enough to reduce geometric frustration, crystalline particles with a body center cubic symmetry (bcc) heterogeneously nucleates on the growing clusters. The volume fraction of the crystalline phase is strongly dependant on the depth of quench. At deep quenches, the SD mechanism produces amorphous structures arranged in dense polytetrahedral aggregates.