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Thermodynamics of Cluster Freezing: a study of the phase behavior of multiple-occupancy crystals through simulation
Clusters crystals have been predicted to form in materials, such as in certain dendrimers, with steep and bounded repulsive interparticle interactions. The resulting solids tile space with a periodic lattice, where each site is multiply occupied. This "superlattice" presents novel theoretical and simulation challenge. In order to obtain the equilibrium behavior of cluster crystals it is essential to treat the number of lattice sites as a constraining thermodynamic variable. The resulting free-energy calculations thus differ considerably from schemes used for single-occupancy lattices. Using this approach, the phase diagram and the elastic properties of a cluster crystal are obtained. Surprising mechanical properties emerge, which in turn shed new light on the behavior of other clustering systems.
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