Simulations of Interfaces Between Coexisting Phases: What Do They Tell Us?

Abstract

Interfaces between coexisting phases are ubiquitous in the physics and chemistry of condensed matter: Bloch walls in ferromagnets; antiphase domain boundaries in ordered binary (AB) or ternary alloys; the surface of a liquid droplet against its vapor; boundaries between A-rich regions and B-rich regions in fluid binary mixtures, etc. These interfaces control material properties in many ways (e.g., when a fluid polymer mixture is frozen-in to form an amorphous material, the mechanical strength of this macromolecular glass is controlled by the extent that A-polymers are entangled with B-polymers across the interface, etc.). For a detailed understanding of the properties of such interfaces, one must consider their structure from the scale of “chemical bonds” between atoms in the interfacial region up to much larger, mesoscopic, scales (e.g., when one tries to measure a concentration profile across an interface between coexisting phases in a partially unmixed polymer blend by suitable depth profiling methods, typical results for the interfacial width are of the order of 50 nm [1]). So from the point of view of simulations, one deals with a multiscale problem [2].