[N]pT Monte Carlo Simulations of the Cluster-Crystal-Forming Penetrable Sphere Model

Abstract

Certain models with purely repulsive pair interactions can form cluster crystals with multiply-occupied lattice sites. Simulating these models' equilibrium properties is, however, quite challenging. Here, we develop an expanded isothermal-isobaric $[N]pT$ ensemble that surmounts this problem by allowing both particle number and lattice spacing to fluctuate. We apply the method with a Monte Carlo simulation scheme to solve the phase diagram of a prototypical cluster-crystal former, the penetrable sphere model (PSM), and compare the results with earlier theoretical predictions. At high temperatures and densities, the equilibrium occupancy $n_{\mathrm{c}}^{\mathrm{eq}}$ of face-centered cubic (FCC) crystal increases linearly. At low temperatures, although $n_{\mathrm{c}}^{\mathrm{eq}}$ plateaus at integer values, the crystal behavior changes continuously with density. The previously ambiguous crossover around $T\sim 0.1$ is resolved.

References in corpus (5)

• A superfluid-droplet crystal and a free-space supersolid in a dipole-blockaded gas
• Phase coexistence of cluster crystals: beyond the Gibbs phase rule
• Diffusion and Relaxation Dynamics in Cluster Crystals
• Molecular dynamics simulation study of self-diffusion for penetrable-sphere model fluids
• Free Energy of Multiple Overlapping Chains

Cited by in corpus (9)

• Equilibrium Phase Behavior of a Continuous-Space Microphase Former
• Recent Advances in the Theory and Simulation of Model Colloidal Microphase Formers
• Hexatic phase and cluster crystals of two-dimensional GEM4 spheres
• Ground state of weakly repulsive soft-core bosons on a sphere
• Freezing of soft-core bosons at zero temperature: A variational theory
• Probing the existence of phase transitions in one-dimensional fluids of penetrable particles
• Demixing cascades in cluster crystals
• Slow dynamics coupled with cluster formation in ultrasoft-potential glasses
• [N]pT ensemble and finite-size scaling study of the GEM-4 critical isostructural transition