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-symmetr
ic 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.
We investigate the phase behaviour of a system of particles interacting through the exp-6 pair potential, a model interaction that is appropriate to describe effective interatomic forces under high compression. The soft-repulsive component of the pot
ential is being varied so as to study the effect on reentrant melting and density anomaly. Upon increasing the repulsion softness, we find that the anomalous melting features persist and occur at smaller pressures. Moreover, if we reduce the range of downward concavity in the potential by extending the hard core at the expenses of the soft-repulsive shoulder, the reentrant part of the melting line reduces in extent so as it does the region of density anomaly.
