Structural and dynamical anomalies of soft particles interacting through harmonic repulsions

Abstract

Molecular dynamics (MD) simulations are carried out to investigate the structural and dynamical anomalies in the core-softened fluid with harmonic repulsions. At sufficiently low temperature and densities, a general scaling relation between the Rosenfeld diffusivity D_R and excess entropy S_ex holds true because the ultrasoft particles tend to avoid overlapping and behave like effective hard spheres. When the temperature is increased high enough, the system acts as a weakly correlated mean-field fluid so that an alternative scaling relation between temperature scaled diffusion D_T and S_ex does work. Interestingly, the plots of D_Rversus two-body excess entropy S₂ approximately collapse onto a single master curve despite the structural and dynamical anomalies, which has also been observed in other core-softened fluids with bounded potential.