Phase diagram of spherical particles interacted with harmonic repulsions

We construct the phase diagram of spherical particles interacted with harmonic repulsions, which are ultrasoft and bounded at fully overlapping. This simple potential form can be used for describing the thermodynamic properties and dynamic behavior of interpenetrable globular micelles, microgels, starlike polymer solutions, and so on. Using dissipative particle dynamics simulations combined with thermodynamic integration, we compute chemical potentials of fluid phase and a number of crystal structures. In addition to the face-centered cubic and body-centered cubic structures, we also find the tetragonal, hexagonal, orthorhombic, and diamond crystal structures stable for this system. In the phase diagram, we identify multiple re-entrant melting regions and polymorphic transitions between the crystals. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3548886]