Emergent tetratic order in crowded systems of rotationally asymmetric hard kite particles

Zhanglin Hou,Yiwu Zong,Fangfu Ye,Zhaoyan Sun,Kun Zhao,Thomas G Mason

doi:10.1038/s41467-020-15723-w

Abstract

Considering multi-body systems of monodisperse hard Brownian particles, it remains challenging to predict the forms of order that can emerge in their dense assembled structures. Surprisingly, here, using Monte Carlo simulations, we show that tetratic-ordered phases emerge in a dense two-dimensional system of hard kites that are rotationally asymmetric and have opposite 72° and α ≈ 90° internal angles. We observe a new tetragonal rectangular crystal (TRX) phase possessing (quasi-)long-range fourfold molecular-orientational order. We propose a method based on local polymorphic configurations of neighboring particle pairs (LPC-NPPs) to understand this emergent tetratic order and show that LPC-NPPs can be useful for predicting orientational order in such systems. To examine the dependence of the tetratic order on α, we apply LPC-NPP analysis to other hard kites for 54° ≤ α ≤ 144°. Our work provides insight into the creation of novel ordered materials by rationally designing particle shape based on anticipated LPC-NPPs.

Highlights

Considering multi-body systems of monodisperse hard Brownian particles, it remains challenging to predict the forms of order that can emerge in their dense assembled structures
Like the hexagonal rotator crystal, which havelong-range positional order and short-range orientational order, Shen et al.[26] showed that their appearance in systems of regular polygons is dependent on the compatibility between the symmetry group of the particle shape and that of the local environment in the crystal
Considering tetratic order, there has been no prior example of tetratically ordered phases, either crystalline or liquid crystalline, based on a particle shape that does not possess at least some form of rotational symmetry

Summary

Introduction

Considering multi-body systems of monodisperse hard Brownian particles, it remains challenging to predict the forms of order that can emerge in their dense assembled structures. In different 2D systems consisting of hard polygons, Shen et al.[26] reported a discrete plastic crystal of 8, 9, 10-gons in which the distribution of particle orientations have multiple peaks, which indicate that hard polygons can be possible candidates for assembling colloidal molecular crystals. Such discrete plastic crystals only show short-range order in molecularorientation. 2D discrete plastic crystals possessing (quasi)long-range molecular-orientational order have not been assembled by slowly crowding hard rotationally anisotropic particles; all prior examples all involve particle shapes that are at least twofold rotationally symmetric. We propose a LPC-NPPs method to understand this emergent tetratic order and show that LPC-NPPs can be useful for predicting orientational order in such systems

Methods

Results

Conclusion