Seminars Archive
Non-classical freezing of hard cube colloids
Computational Physics, Faculty of Physics, University of Vienna, Austria
Abstract
Classical nucleation theory (CNT) is the most prominent phenomenological theory to describe first order phase transitions. In CNT, spherical droplets of the new stable phase grow within the old, metastable phase via an one-step Markov process. Despite its great success in predicting nucleation rate and free energy barrier trends in a wide variety of systems, there is a growing number of phenomena that do not fit into the CNT framework and those cases are subsumed under the term ”non-classical nucleation”.
In this work [1] we provide strong computational evidence that hard colloidal cubes, a system whose thermodynamic properties have been studied experimentally [2] as well as theoretically [3], crystallise via a non-classical two-step process: We observe that orientational order precedes cubic crystalline order and more specifically, that orientational order acts as template for the cubic lattice to grow on. This dominance of the orientational ordering during the transition suggests that the hard cube crystallisation bears in fact a greater resemblance to the isotropic-nematic transition in liquid crystals than to the crystallisation of conventional isotropic colloids
Concluding, we have shown through the the use of kinetic Monte Carlo simulations that hard cube colloids, a relatively simple system, exhibits a complex freezing behaviour and we hope that this research inspires further studies of the freezing of anisotropic colloids.
REFERENCES
[1] "Non classical freezing of hard cube colloids", Carina Karner and
Christoph Dellago, to be submitted
[2] Laura Rossi, Vishal Soni, Douglas J Ashton, David J Pine, Albert P
Philipse, Paul M Chaikin, Marjolein Dijkstra, Stefano Sacanna,
and William T M Irvine. Shape- sensitive crystallization in colloidal
superball fluids. Pro- ceedings of the National Academy of Sciences of
the United States of America, 112(17):5286–90, 2015.
[3] Umang Agarwal and Fernando A Escobedo. Mesophase behaviour of
polyhedral particles. Nat Mater, 10(3):230–235, 2011
