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Directed Self-Assembly of Polarizable Ellipsoids in an External Electric Field

Azari, Arash, Crassous, Jérôme J., Mihut, Adriana M., Bialik, Erik, Schurtenberger, Peter, Stenhammar, Joakim, Linse, Per
Langmuir 2017 v.33 no.48 pp. 13834-13840
Monte Carlo method, colloids, crystal structure, electric field, electrostatic interactions, models
The interplay between shape anisotropy and directed long-range interactions enables the self-assembly of complex colloidal structures. As a recent highlight, ellipsoidal particles polarized in an external electric field were observed to associate into well-defined tubular structures. In this study, we systematically investigate such directed self-assembly using Monte Carlo simulations of a two-point-charge model of polarizable prolate ellipsoids. In spite of its simplicity and computational efficiency, we demonstrate that the model is capable of capturing the complex structures observed in experiments on ellipsoidal colloids at low volume fractions. We show that, at sufficiently high electric field strength, the anisotropy in shape and electrostatic interactions causes a transition from three-dimensional crystal structures observed at low aspect ratios to two-dimensional sheets and tubes at higher aspect ratios. Our work thus illustrates the rich self-assembly behavior accessible when exploiting the interplay between competing long- and short-range anisotropic interactions in colloidal systems.