We find that a system of particles interacting through a simple isotropic potential with a softened core is able to exhibit a rich phase behavior including: a liquid-liquid phase transition in the supercooled phase, as has been suggested for water; a gas-liquid-liquid triple point; a freezing line with anomalous reentrant behavior. The essential ingredient leading to these features resides in that the potential investigated gives origin to two effective core radii.
@article{arxiv.cond-mat/0005214,
title = {Simple Fluids with Complex Phase Behavior},
author = {G. Malescio and G. Pellicane},
journal= {arXiv preprint arXiv:cond-mat/0005214},
year = {2009}
}