An ubiquitous mechanism for water-like anomalies

¹  Universidade Federal do Rio Grande do Sul, Instituto de Física - 91501-970, Porto Alegre, RS, Brazil
²  Universidade Federal do Rio Grande do Sul, Instituto de Química - 91501-970, Porto Alegre, RS, Brazil

Corresponding author: oliveira@if.ufrgs.br

Received: 17 July 2008
Accepted: 11 January 2009

Abstract

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, λ, from a ramp (λ = 0.5) to a square-shoulder potential (λ =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.