Structural anomalies for a three dimensional isotropic core-softned potential

Abstract

Using molecular dynamics simulations we investigate the structure of a system of particles interacting through a continuous core-softened interparticle potential. We found for the translational order parameter t a local maximum at a density ρt-max and a local minimum at ρt-min>ρt-max. Between ρt-max and ρt-min, the t parameter anomalously decreases upon increasing pressure. For the orientational order parameter Q6 a maximum was observed at a density ρt-max<ρQmax<ρt-min. For densities between ρQmax and ρt-min, both the translational (t) and orientational (Q6) order parameters have anomalous behavior. We know that this system also exhibits density and diffusion anomalies. We found that the region in the pressure-temperature phase diagram of the structural anomaly englobes the region of the diffusion anomaly that is larger than the region limited by the temperature of maximum density. This cascade of anomalies (structural, dynamic, and thermodynamic) for our model has the same hierarchy as that observed for the simple point charge/extended water.