Stress-induced microcracking and cooperative motion of cold dusty plasma liquids

Avalanche structural rearrangement through cracking-healing in weakly stressed cold dusty plasma liquids

We experimentally investigate the spatiotemporal dynamical behaviors of the avalanche structural rearrangement through micro-cracking-healing in weakly stressed cold dusty plasma liquids, and the kinetic origins for their different spatial and temporal classifications. The crystalline ordered domains can be cracked or temporarily sustain and transfer the weak stress to remote regions for cracking-healing. It is found that cracking sites form a fractal network with cluster size following power law distribution in the xyt space. The histograms of the persistent times for sustaining regional ordered and disordered structure, the temporal cracking burst width, and quiescent time between two bursts all follow power law decays with fast descending tails. Cracking can be classified into a single temporal burst with simple line like spatial patterns and the successive cracking fluctuation with densely packed cracking clusters. For an ordered region, whether the Burgers vectors of the incoming dislocations from the boundary allow direct dislocation reduction is the key for the above two classifications through cracking a large ordered domain into medium scale corotating ordered domains or small patches. The low regional structural order at the end of a cracking burst can be regarded as an alarm for predicting the short quiescent period before the next cracking burst.

Kinetic origin of grain boundary migration, grain coalescence, and defect reduction in the crystallization of quenched two-dimensional Yukawa liquids

The kinetic origin of grain boundary migration, grain coalescence, and defect reduction in the crystallization of quenched two-dimensional Yukawa liquids are numerically investigated. It is found that, in grain coalescence, stick-slip cracking the region in front of the grain boundary into smaller subgrains corotating with small angle, followed by healing, is the key for aligning lattice misorientation and inducing grain boundary stick-slip advance. Cracking is initiated from the weakly interlocked dislocation along its Burgers vector, which in turn causes dislocation motion along the crack. The cascaded scattering and recombination of two dislocations with 60^{∘} and 120^{∘} Burgers vector angle difference into two and one dislocations are the major processes for dislocation motion and reduction, respectively, in grain boundary migration. A rough grain boundary with large curvature easily supports the above process and induces high grain boundary mobility. Along a straight smooth grain boundary, the parallel Burgers vectors of the string of dislocations hinder defect reduction and induce coalescence stagnation.