Recrystallization in string-fluid complex plasmas

Abstract

Complex plasmas, i.e., low-temperature plasmas containing suspensions of solid microparticles, exhibit electrorheological properties which are manifested by the formation of stringlike clusters (SLCs) in microgravity experiments. It is thought that SLCs form due to a long-range effective attraction between the particles under the influence of a directed ion flow. We performed molecular dynamics (MD) simulations of negatively charged microparticles with positive model wakes to mimic the effect of ion flow in experiments, and achieved SLC formation without long-range attraction between the microparticles. We show that long-range-reduced repulsion was enough to obtain the SLCs similar to the experiments and found that the simulations with the long-range attraction became unstable due to particle accelerations. Destruction and recrystallization of the stringlike structure was also studied experimentally using the Plasmakristall-4 facility on board the International Space Station, and the experimental findings were compared to those from three–dimensional MD simulations. We found excellent qualitative agreement between simulation and experiment when recrystallization was simulated using an interparticle potential without effective long-range attraction.