Hard spheres confined to narrow, quasi-one-dimensional channels have been shown, in experiment [1] and simulation studies [2,3], to spontaneously form structures not observed in the bulk, such as single, double and triple helices, depending on the diameter of the channel. These helices are inherently chiral, despite being formed from non-chiral substituents, and the chirality of the perfect structures can be easily described in terms of their right hand (P) and left hand (M) twist directions. However, the presence of defect pairs in the helix that locally reverse the twist direction [4] complicate the identification of chiral structures. This work explores the use of geometric chirality measures for the identification of chirality and shows that the concentration and distribution of the defects has a significant effect.

Right-handed Helix

Left-handed Helix

Helix with defects

1. Jiang L, de Folter JW, Huang J, Philipse AP, Kegel WK, Petukhov AV. Helical Colloidal Sphere Structures through Thermo‐Reversible Co‐Assembly with Molecular Microtubes. Angewandte Chemie. 2013 Mar 18;125(12):3448-52.
2. Pickett GT, Gross M, Okuyama H. Spontaneous chirality in simple systems. Physical Review Letters. 2000 Oct 23;85(17):3652.
3. Mughal AD, Chan HK, Weaire D, Hutzler ST. Dense packings of spheres in cylinders: Simulations. Physical Review E. 2012 May 11;85(5):051305.
4. Zarif M, Spiteri RJ, Bowles RK. Inherent structure landscape of hard spheres confined to narrow cylindrical channels. Physical Review E. 2021 Dec 3;104(6):064602.