A hybrid helical structure of hard-sphere packing from sequential deposition

Abstract

A hybrid helical structure of equal-sized hard spheres in cylindrical confinement was discovered as a ‘by-product’ of the recently developed sequential deposition approach [Physical Review E 84, 050302(R) (2011)] for constructing the densest possible packings of such systems. Unlike the conventional triple-helix structure where its three strands of spheres are packed densely to form triads of close-packed, mutually touching spheres, in this novel helical phase, only two of its three strands of spheres are packed in this densest arrangement and the overall structure resembles a hybrid of the single and the double helix. This article explains how this previously unknown structure can be constructed via the abovementioned sequential deposition of spheres, which involves manipulating the positions of a few spheres to create a template for the deposition process. The findings show that it is possible to discover new structures through varying only the configuration of the few spheres that form the template, where this approach relies on a sensitive dependence of the deposition-generated structures on the template.

Keywords:

• deposition
• self-assembly
• structure

Acknowledgements

This work was supported by the Irish Research Council through an EMPOWER Post-doctoral Fellowship (Dec 2010 - Dec 2012). Prof. Tony Stace and Dr. Alexander Markevich, both from the School of Chemistry of the University of Nottingham, have kindly helped to proofread the original manuscript. Indispensible support from Chloe Po-Yee Wong at a time of uncertain future is gratefully acknowledged.