Orientational ordering and layering of hard plates in narrow slit-like pores

TL;DR

This study uses density functional theory to analyze how hard plate-like particles organize in narrow slit pores, revealing multiple phase transitions including layering and orientational order changes.

Contribution

It introduces a theoretical analysis of phase behavior of hard plates in confined geometries, highlighting new layering and orientational transitions.

Findings

Perpendicular face-on orientation at low densities

Layering transition between n and n+1 layers at intermediate densities

Biaxial nematic phase transition at high densities

Abstract

We examine the ordering behavior of hard plate-like particle in a very narrow slit-like pore using the Parsons-Lee density functional theory and the restricted orientation approximation. We observe that the plates are orientationally ordered and align perpendicularly (face-on) to the walls at low densities, a first order layering transition occurs between uniaxial nematic structures having n and n+1 layers at intermediate densities and even a phase transition between a monolayer with parallel (edge-on) orientational order and n layers with perpendicular one can be detected at high densities. In addition to this, the edge-on monolayer is usually biaxial nematic and a uniaxial-biaxial nematic phase transition can be also seen at very high densities.