Anomalous phase behavior in a model fluid with only one type of local structure

We present evidence that the concurrent existence of two populations of particles with different effective diameters is not a prerequisite for the occurrence of anomalous phase behaviors in systems of particles interacting through spherically-symmetric unbounded potentials. Our results show that an extremely weak softening of the interparticle repulsion, yielding a single nearest-neighbor separation, is able to originate a wide spectrum of unconventional features including reentrant melting, solid polymorphism, as well as thermodynamic, dynamic, and structural anomalies. These findings extend the possibility of anomalous phase behavior to a class of systems much broader than currently assumed.