Predictive orientational phase behavior in convex polyhedral entropic crystals

TL;DR

This study uses Monte Carlo simulations to establish a predictive relationship between shape attributes of convex polyhedra and their orientational phases in crystalline assemblies, advancing understanding of self-assembly in anisotropic particles.

Contribution

It identifies key shape attributes that determine orientational phases in polyhedral crystals, providing a predictive framework for their self-assembly behavior.

Findings

Shape attributes control orientational phases.

Translational order influences only DPC phase.

Shape parameters predict phase transitions under pressure.

Abstract

Hard convex polyhedra, idealized models for anisotropic colloids and nanoparticles, are known to form variety of orientational phases despite the regular arrangement of particles in the crystalline assemblies. Based on the orientational behavior of the constituents particles, such phases could be categorized into freely rotating plastic crystals (PC), discrete plastic crystals (DPC) and orientationally ordered crystals (OC). In this article, we report an extensive Monte Carlo computer simulation study of sixty hard convex polyhedral shape indicating a direct predictive relationship between the nature of orientational phases in the crystalline assemblies and single-particle shape attributes. The influence of three attributes namely; (i) Isoperimetric Quotient (IQ) i.e., the extent of asphericity; (ii) isotropy of the moment of inertia tensor in the principal frame and (iii) number of symmetry operations in the point group of the particle and self-assembled crystal structure, were observed to control the orientational phase behavior of the entire solid region in many-body system. The translational order in the crystal appeared to play significant role only in the DPC phase, where as, other two phases were completely governed by the combination of two attributes. In this study, the role of shape attributes were characterized by sequential appearance of one or two of the aforementioned rotational phases across the phase diagram in a pressure dependent manner which could be regarded as an important stepping stone towards fully predictive self-assembly behavior of hard particle systems.