Merging and hopping processes in systems of ultrasoft, cluster forming particles under compression

We have exposed a two-dimensional nanodrop of particles interacting via an ultrasoft (i.e., bounded), purely repulsive potential to a combined thermo- and barostat. While increasing the pressure steadily via a suitable pressure increment the temperature of the system is kept at a fixed target temperature. Once the hexagonal crystal composed of clusters of overlapping particles has formed, we investigate the system's reaction on the non-equilibrium conditions. Recording the trajectories of the particles in molecular dynamics simulations, we can identify how particle hopping and cluster merging events are realized. We find that the number of particles involved in these processes is of comparable size and that under-populated clusters (with ∼70% of the average cluster size) are prone for merging processes. Theoretical predictions about the density-dependence of the average cluster size and of the nearest cluster-distance are confirmed within good accuracy.