Phase behavior and design rules for plastic colloidal crystals of hard polyhedra <i>via</i> consideration of directional entropic forces

Karas, Andrew S.; Dshemuchadse, Julia; Anders, Greg van; Glotzer, Sharon C.

doi:10.1039/c8sm02643b

Cited by 14 publications

(17 citation statements)

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“…The dimers within this arrangement were randomly oriented with respect to the DEP field direction, reminiscent of a plastic crystal (PC), a mesophase with long-range translational order but lacking strict orientational order. 54 The orientation distribution of the dimer particles, however, indicated a preferred orientation with the field, consistent with a so-called "discrete" PC phase, in which the particle and local environment share some but not all nontrivial symmetry elements (Figure S7A), such that preferred particle orientations recover the absent symmetry elements of the assembly. 44 The formation of PC phases perhaps is not surprising for dimers with low β values, as these particles begin to approximate isotropic spheres that would be expected to rotate more freely and be less prone to alignment in the DEP field.…”

Section: ■ Results and Discussionmentioning

confidence: 58%

“…Surprisingly, dimer(1.00,0.31) particles also packed in a hexagonal lattice (Figure B). The dimers within this arrangement were randomly oriented with respect to the DEP field direction, reminiscent of a plastic crystal (PC), a mesophase with long-range translational order but lacking strict orientational order . The orientation distribution of the dimer particles, however, indicated a preferred orientation with the field, consistent with a so-called “discrete” PC phase, in which the particle and local environment share some but not all nontrivial symmetry elements (Figure S7A), such that preferred particle orientations recover the absent symmetry elements of the assembly .…”

Section: Resultsmentioning

confidence: 99%

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Assembly of Shape-Tunable Colloidal Dimers in a Dielectrophoretic Field

et al. 2020

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The shape of colloid particles plays an important role in directing the structure of their assemblies. Anisotropic colloids can adopt more complex structures than can their spherical counterparts, illustrated here by organosilica dimers fabricated with precise control of particle shape. Dielectrophoretic fields were used to coerce the assembly of 19 uniquely shaped dimers, which allowed direct visualization of the assembly process as well as the structure, symmetry, and long-range order (or lack thereof) of the final state. The various particle shapes resulted in crystalline phases with p6m, cmm, or p2 plane group symmetries, two plastic phases, and a disordered phase. The observations establish a relationship between particle shape and the resulting 2D structures, providing guidance for the design of 2D colloidal crystals.

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Section: ■ Results and Discussionmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%

Assembly of Shape-Tunable Colloidal Dimers in a Dielectrophoretic Field

et al. 2020

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“…In this case, an orientationally-ordered crystalline phase is not inherently more favorable, since many orientations of nanocrystals would result in the same entropy for the system 23,24 . The orientational glass phase was reported in simulations by Glotzer and coworkers for pseudorhombicuboctahedron hard particles, where nanoparticles adopted a set of only six distinct orientations at high packing density 25 .…”

Section: Isotropic Vs Anisotropic Nanocrystalsmentioning

confidence: 91%

Observation of an Orientational Glass in a Superlattice of Elliptically-Faceted CdSe Nanocrystals

et al. 2022

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Extensive prior work has shown that colloidal inorganic nanocrystals coated with organic ligand shells can behave as artificial atoms and, as such, form superlattices with different crystal structures and packing densities. Although ordered superlattices present a high degree of longrange positional order, the relative crystallographic orientation of the inorganic nanocrystals with respect to each other tends to be random. Recent works have shown that superlattices can achieve orientational alignment through combinations of nanocrystal faceting and ligand modification, as well as selective metal particle attachment to particular facets. These studies have focused on the assembly of high-symmetry nanocrystals, such as cubes and cuboctahedra.Here, we study the assembly of elliptically-faceted CdSe/CdS core/shell nanocrystals with one unique crystallographic orientation along the major elliptical axis. We show that the nanocrystals form an unexpectedly well-ordered translational superlattice, with a degree of order comparable to that achieved with higher-symmetry nanocrystals. Additionally, we show that, due to the particles' faceted shape, the superlattice is characterized by an orientational glass phase in which only certain orientations are possible due to entropically-frustrated crystallization. In this phase, the nanocrystals do not exhibit a local orientational ordering but rather have distinct orientations that emerge at different locations within the same domain. The distinct orientations are a result of a facet-to-facet lock-in mechanism that occurs during the self-assembly process. These facet-tofacet alignments force the nanocrystals to tilt on different lattice planes forming different projections that we termed apparent polydispersity. Our experimental realization of an orientational glass phase for multifaceted semiconducting nanocrystals will allow further 3 investigation of how this phase is formed and how it can be utilized for potential optical, electrical, and thermal transport applications.

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“…The method accounts for symmetry by accepting an array of equivalent quaternions corresponding to all symmetry-preserving operations in the rotation group of interest. This metric can be used as an order parameter for measuring orientational disorder in plastic crystals, which exhibit translational order and orientational disorder [50].…”

Section: Angular Separationmentioning

confidence: 99%

freud: A software suite for high throughput analysis of particle simulation data

Ramasubramani

Dice

Harper

et al. 2020

Computer Physics Communications

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The freud Python package is a powerful library for analyzing simulation data. Written with modern simulation and data analysis workflows in mind, freud provides a Python interface to fast, parallelized C++ routines that run efficiently on laptops, workstations, and supercomputing clusters. The package provides the core tools for finding particle neighbors in periodic systems, and offers a uniform API to a wide variety of methods implemented using these tools. As such, freud users can access standard methods such as the radial distribution function as well as newer, more specialized methods such as the potential of mean force and torque and local crystal environment analysis with equal ease. While many comparable tools place a heavy emphasis on reading and operating on trajectory file formats, freud instead accepts numerical arrays of data directly as inputs. By remaining agnostic to its data source, freud is suitable for analyzing any coarse-grained particle simulation, regardless of the original data representation or simulation method. When used for on-the-fly analysis in conjunction with scriptable simulation software such as HOOMD-blue [1, 2], freud enables smart simulations that adapt to the current state of the system, allowing users to study phenomena such as nucleation and growth. PROGRAM SUMMARYProgram Title: freud Licensing provisions: BSD 3-Clause Programming language: Python, C++ Nature of problem: Simulations of coarse-grained, nano-scale, and colloidal particle systems typically require analyses specialized to a particular system. Certain more standardized techniques -including correlation functions, order parameters, and clustering -are computationally intensive tasks that must be carefully implemented to scale to the larger systems common in modern simulations. Solution method: freud performs a wide variety of particle system analyses, offering a Python API that interfaces with many other tools in computational molecular sciences via NumPy array inputs and outputs. The algorithms in freud leverage parallelized C++ to scale to large systems and enable real-time analysis. The library's broad set of features encode few assumptions compared to other analysis packages, enabling analysis of a broader class of data ranging from biomolecular simulations to colloidal experiments. Unusual features:1. freud provides very fast, parallel implementations of standard analysis methods like RDFs and correlation functions. 2. freud includes the reference implementation for the potential of mean force and torque (PMFT). 3. freud provides various novel methods for characterizing particle environments, including the calculation of descriptors useful for machine learning. Additional comments:The source code is hosted on GitHub (https://github. com/glotzerlab/freud), and documentation is available online (https: //freud.readthedocs.io/). The package may be installed via pip install freud-analysis or conda install -c conda-forge freud. 13 for i, p in enumerate(points): 14 for j in nl.index_j[nl.index_i == i]: 15 for k in...

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Phase behavior and design rules for plastic colloidal crystals of hard polyhedra via consideration of directional entropic forces

Abstract: We show how directional entropic forces (which are set by particle shape) give rise to distinct behaviors in entropic systems with translational order and orientational disorder.

Cited by 14 publications

References 33 publications

Assembly of Shape-Tunable Colloidal Dimers in a Dielectrophoretic Field

Assembly of Shape-Tunable Colloidal Dimers in a Dielectrophoretic Field

Observation of an Orientational Glass in a Superlattice of Elliptically-Faceted CdSe Nanocrystals

freud: A software suite for high throughput analysis of particle simulation data

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