Reexamination of string phase and shear thickening in simple fluids

In 1984, Erpenbeck observed a shear-induced alignment of particles into strings in nonequilibrium molecular dynamics simulations of hard spheres. Since then, it has remained unclear if this effect was genuine or if it arose from the use of a thermostat which assumed an incorrect form for the velocity profile. All studies performed up to now have focused on improving the accuracy with which the velocity profile is determined. We propose here a radically different approach: we apply a recently developed configurational expression for the temperature. This expression does not require any knowledge of the streaming velocity profile. Using a configurational thermostat, we show that the string phase is an artifact and we observe a shear-thickening regime, as seen in experiments on concentrated "hard-sphere"-like colloidal dispersions.