Transport coefficients of soft repulsive particle fluids

Molecular dynamics computer simulation has been used to compute the self-diffusion coefficient, D, and shear viscosity, η(s), of soft-sphere fluids, in which the particles interact through the soft-sphere pair potential, φ(r) = ϵ(σ/r)(n), where n measures the steepness or stiffness of the potential, ϵ and σ are a characteristic energy and distance, respectively. The simulations were carried out on monodisperse systems for a range of n values from the hard-sphere ([Formula: see text]) limit down to n = 4 over a range of densities. An ideal glass transition value was estimated from the limit where D and [Formula: see text] for each value of n. Nucleation of the crystalline phase was found to intervene prior to the formation of the glass itself, as has been found previously for hard spheres (i.e. [Formula: see text]). With increasing softness the glass transition moves further within the solid part of the phase diagram, as predicted by Cardenas and Tosi (2005 Phys. Lett. A 336 423), although the volume fractions at the glass transition estimated by the current procedure here are systematically lower than the predictions of that study.