An ubiquitous mechanism for water-like anomalies

Using collision-driven molecular dynamics a system of spherical particles interacting through an effective two-length-scales potential is studied. The potential can be tuned by means of a single parameter, lambda, from a ramp (lambda = 0.5) to a square-shoulder potential (lambda = 1.0) representing a family of two-length-scales potentials in which the shortest interaction distance has higher potential energy than the largest interaction distance. For all the potentials, ranging between the ramp and the square-shoulder, density and structural anomalies were found, while the diffusion anomaly is found in all but in the square-shoulder potential. The presence of anomalies in square-shoulder potential, not observed in previous simulations, confirms the assumption that the two-length-scales potential is an ubiquitous ingredient for a system to exhibit water-like anomalies. Copyright (C) EPLA, 2009