1 research outputs found
Cluster glasses of ultrasoft particles
We present molecular dynamics (MD) simulations results for dense fluids of
ultrasoft, fully-penetrable particles. These are a binary mixture and a
polydisperse system of particles interacting via the generalized exponential
model, which is known to yield cluster crystal phases for the corresponding
monodisperse systems. Because of the dispersity in the particle size, the
systems investigated in this work do not crystallize and form disordered
cluster phases. The clustering transition appears as a smooth crossover to a
regime in which particles are mostly located in clusters, isolated particles
being infrequent. The analysis of the internal cluster structure reveals
microsegregation of the big and small particles, with a strong
homo-coordination in the binary mixture. Upon further lowering the temperature
below the clustering transition, the motion of the clusters' centers-of-mass
slows down dramatically, giving way to a cluster glass transition. In the
cluster glass, the diffusivities remain finite and display an activated
temperature dependence, indicating that relaxation in the cluster glass occurs
via particle hopping in a nearly arrested matrix of clusters. Finally we
discuss the influence of the microscopic dynamics on the transport properties
by comparing the MD results with Monte Carlo simulations.Comment: 17 pages, 23 figure