Sequences of dislocation reactions and helicity transformations in tubular crystals

TL;DR

This paper investigates the complex defect dynamics and helicity transformations in tubular crystals using Langevin simulations, revealing new irreversible defect reactions and methods to control them.

Contribution

It extends previous elastic network models by employing Langevin dynamics to explore defect behaviors and introduces control strategies for defect sequences in tubular crystals.

Findings

Dislocation glide multistability confirmed.

Irreversible defect transformations observed.

External forces can control defect sequences.

Abstract

Freestanding tubular crystals offer a general description of crystalline order on deformable surfaces with cylindrical topology, such as single-walled carbon nanotubes, microtubules, and recently reported colloidal assemblies. These systems exhibit a rich interplay between the crystal's helicity on its periodic surface, the deformable geometry of that surface, and the motions of topological defects within the crystal. Previously, in simulations of tubular crystals as elastic networks, we found that dislocations in nontrivial patterns can co-stabilize with kinks in the tube shape, producing mechanical multistability. Here, we extend that work with detailed Langevin dynamics simulations, in order to explore defect dynamics efficiently and without the constraints imposed by elastic network models. Along with the predicted multistability of dislocation glide, we find a variety of irreversible defect transformations, including vacancy formation, particle extrusions, and "reactions" that reorient dislocation pairs. Moreover, we report spontaneous sequences of several such defect transformations, which are unique to tubular crystals. We demonstrate a simple method for controlling these sequences through a time-varying external force.