Abstract.
The annihilation of the nematic hedgehog and anti-hedgehog within an infinite cylinder of radius R is studied. The semi-microscopic lattice-type model and Brownian molecular dynamics are used. We distinguish among the i) early pre-collision, ii) late pre-collision, iii) early post-collision, and iv) late post-collision stages. In the pre-collision stage our results agree qualitatively with the existing experimental observations and also continuum-type simulations. The core of each defect exhibits a ring-like structure, where the ring axis is set perpendicular to the cylinder symmetry axis. For ξ(0)d/(2R) > 1 the interaction between defects is negligible, where ξ(0)d describes the initial separation of defects. Consequently, the defects annihilate within the simulation time window for ξ(0)d/(2R) < 1. For close enough defects their separation scales as ξd \( \varpropto\) (tc - t)0.4±0.1, where tc stands for the collision time. In elastically anisotropic medium the hedgehog is faster than the anti-hedgehog. In the early pre-collision stage the defects can be treated as point-like particles, possessing inherent core structure, that interact via the nematic director field. In the late pre-collision stage the cores reflect the interaction between defects. After the collision a charge-less ring structure is first formed. In the early post-collision stage the ring adopts an essentially untwisted circular structure of the radius ξr. In the late post-collision stage we observe two qualitatively different scenarios. For μ = ξr/R < μc ∼ 0.25 the ring collapses leading to the escaped radial equilibrium structure. For μ > μc the chargeless ring triggers the nucleation growth into the planar polar structure with line defects.
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Svetec, M., Kralj, S., Bradač, Z. et al. Annihilation of nematic point defects: Pre-collision and post-collision evolution. Eur. Phys. J. E 20, 71–79 (2006). https://doi.org/10.1140/epje/i2005-10120-9
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DOI: https://doi.org/10.1140/epje/i2005-10120-9