1808.10729v1.pdf (3.11 MB)
Download file

Density functional theory for the crystallization of two-dimensional dipolar colloidal alloys.

Download (3.11 MB)
journal contribution
posted on 27.09.2018, 09:58 by W.R.C. Somerville, J.L. Stokes, A.M. Adawi, T.S. Horozov, Andrew ArcherAndrew Archer, D.M.A. Buzza
Two-dimensional mixtures of dipolar colloidal particles with different dipole moments exhibit extremely rich self-assembly behaviour and are relevant to a wide range of experimental systems, including charged and super-paramagnetic colloids at liquid interfaces. However, there is a gap in our understanding of the crystallization of these systems because existing theories such as integral equation theory and lattice sum methods can only be used to study the high temperature fluid phase and the zero-temperature crystal phase, respectively. In this paper we bridge this gap by developing a density functional theory (DFT), valid at intermediate temperatures, in order to study the crystallization of one and two-component dipolar colloidal monolayers. The theory employs a series expansion of the excess Helmholtz free energy functional, truncated at second order in the density, and taking as input highly accurate bulk fluid direct correlation functions from simulation. Although truncating the free energy at second order means that we cannot determine the freezing point accurately, our approach allows us to calculate \emph{ab initio} both the density profiles of the different species and the symmetry of the final crystal structures. Our DFT predicts hexagonal crystal structures for one-component systems, and a variety of superlattice structures for two-component systems, including those with hexagonal and square symmetry, in excellent agreement with known results for these systems. The theory also provides new insights into the structure of two-component systems in the intermediate temperature regime where the small particles remain molten but the large particles are frozen on a regular lattice.

Funding

This work was supported by the EPSRC (Grant number EP/L025078/1 Self assembly of two dimensional colloidal alloys for metamaterials applications).

History

School

  • Science

Department

  • Mathematical Sciences

Published in

Journal of Physics: Condensed Matter

Volume

30

Citation

SOMERVILLE, W.R.C. ... et al., 2018. Density functional theory for the crystallization of two-dimensional dipolar colloidal alloys. Journal of Physics: Condensed Matter, 30: 405102.

Publisher

© IOP Publishing

Version

AM (Accepted Manuscript)

Publisher statement

This is an author-created, un-copyedited version of an article published in Journal of Physics: Condensed Matter. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-648X/aaddc9.

Acceptance date

30/08/2018

Publication date

2018-09-13

ISSN

0953-8984

eISSN

1361-648X

Language

en

Location

England