Survey of Morphologies Formed in the Wake of an Enslaved Phase-Separation Front in Two Dimensions

TL;DR

This paper provides a numerical survey of the diverse morphologies formed behind a moving phase-separation front in two dimensions, highlighting how speed and composition influence the resulting structures and their stability.

Contribution

It offers the first comprehensive numerical analysis of morphology formation behind phase-separation fronts, including stability and transition predictions based on front speed and composition.

Findings

Morphologies depend on front speed and composition.

Regular stripe and droplet patterns are observed.

Transition point from orthogonal to parallel stripes predicted analytically.

Abstract

A phase-separation front will leave in its wake a phase-separated morphology that differs markedly from homogeneous phase-separation morphologies. For a purely diffusive system such a front, moving with constant velocity, will generate very regular, non-equilibrium structures. We present here a numerical study of these fronts using a lattice Boltzmann method. In two dimensions these structures are regular stripes or droplet arrays. In general the kind and orientation of the selected morphology and the size of the domains depends on the speed of the front as well as the composition of the material overtaken by the phase-separation front. We present a survey of morphologies as a function of these two parameters. We show that the resulting morphologies are initial condition dependent. We then examine which of the potential morphologies is the most stable. An analytical analysis for symmetrical compositions predicts the transition point from orthogonal to parallel stripes.