Revealing roles of competing local structural orderings in crystallization of polymorphic systems.

Minhuan Li,Hajime Tanaka,Yanshuang Chen,Peng Tan

doi:10.1126/sciadv.aaw8938

Minhuan Li, Hajime Tanaka + Show 2 more

Open Access

https://doi.org/10.1126/sciadv.aaw8938

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Journal: Science advances	Publication Date: Jul 1, 2020
Citations: 18	License type: CC BY 4.0

Affiliation: Tokyo University of Science, Fudan University

Abstract

Most systems have more than two stable crystalline states in the phase diagram, which is known as polymorphism. Crystallization in such a system is often under strong influence of competing orderings linked to those crystals. However, how such competition affects crystal nucleation and ordering toward the final crystalline state is largely unknown. This is primarily because the competition takes place locally and thus is masked by large positional fluctuations. We develop a unique method to correctly identify local symmetries by removing their distortions due to positional fluctuations. This allows us to experimentally access the spatiotemporal fluctuations of local symmetries at a single-particle level in crystallization of a charged colloidal system near the body-centered cubic-face-centered cubic border. Thus, we successfully reveal the crucial roles of competing ordering in the initial selection of polymorphs and the final grain boundary motion toward the most stable state from a microscopic perspective.

Highlights

The crystallization kinetics is one of the most fundamental and important issues in condensed matter physics and materials sciences
The growth of crystal nuclei results in the formation of a polycrystalline mosaic structure, where crystalline grains are separated by grain boundaries [23,24,25,26,27,28,29,30], which can be regarded as intermediate structures and whose slow migrations play a crucial role in the later coarsening and ripening process toward the most stable crystal polymorph [31,32,33,34,35]
Roles: How is the formation of a stable solid realized by passing through such complex intermediates under competing ordering toward different crystals? Is there any universal nature of the intermediates that facilitate the transition? uncovering the nature of the intermediates and clarifying their roles in polymorph selection at a microscopic level are essential for answering these fundamental questions and reaching a full understanding of the crystallization kinetics under competing orderings

Summary

Introduction

The crystallization kinetics is one of the most fundamental and important issues in condensed matter physics and materials sciences. The growth of crystal nuclei results in the formation of a polycrystalline mosaic structure, where crystalline grains are separated by grain boundaries [23,24,25,26,27,28,29,30], which can be regarded as intermediate structures and whose slow migrations play a crucial role in the later coarsening and ripening process toward the most stable crystal polymorph [31,32,33,34,35] These complex intermediates, which are a transient state between a liquid and a solid state, play a critical role in the crystallization kinetics. This scenario leaves us big puzzles about their precise roles: How is the formation of a stable solid realized by passing through such complex intermediates under competing ordering toward different crystals? Is there any universal nature of the intermediates that facilitate the transition? uncovering the nature of the intermediates and clarifying their roles in polymorph selection at a microscopic level are essential for answering these fundamental questions and reaching a full understanding of the crystallization kinetics under competing orderings

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