Finite-size scaling study of shear viscosity anomaly at liquid-liquid criticality

Abstract

We study the equilibrium dynamics of a symmetrical binary Lennard-Jones fluid mixture near its consolute criticality. Molecular dynamics simulation results for the shear viscosity, η, from a microcanonical ensemble are compared with those from a canonical ensemble with various thermostats. It is observed that the Nosé-Hoover thermostat is a good candidate for this purpose, and is therefore adopted for the quantification of the critical singularity of η, to avoid the temperature fluctuations (or even drifts) that are often encountered in microcanonical simulations. Via a finite-size scaling analysis of our simulation data we have been able to confirm that the shear viscosity exhibits a weak critical singularity in agreement with the theoretical predictions.

Coarsening in fluid phase transitions

“…Further, inside the coexistence region, transport properties of droplets (for equilibrium configurations), calculated via NHT, are found to be in good agreement with the calculations using microcanonical ensemble [46,47]. Also, in a binary fluid, critical behavior of shear viscosity was nicely reproduced via NHT [67]. In addition, from the experience, we feel that the NHT provides a superior control over temperature (which is an important criterion), compared to a few other better hydrodynamics preserving thermostats, particularly in out-of-equilibrium situations.…”

“…The objective is to check to what extent the kinetics of vapor-liquid phase separation is similar to that of an incompressible binary liquid. In this context, we must mention that in dynamic critical phenomena [8,56,[67][68][69][70][71][72][73][74] liquid-liquid and vapor-liquid transitions belong to the same universality class. It is important to verify, thus, whether the non-equilibrium dynamics are similar in the two cases.…”

Finite-size scaling study of dynamic critical phenomena in a vapor-liquid transition

“…On the other hand, the situation with respect to dynamics is relatively poor. Simulation studies, that helped achieving the objective for the static phenomena, gained momentum in the context of dynamic critical phenomena only recently [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Such a status is despite the fact that adequate information on the equilibrium transport phenomena is very much essential for the understanding of even nonequilibrium phenomena like the kinetics of phase transitions [9,39].…”

Structure and dynamics of binary liquid mixtures near their continuous demixing transitions

“…In particular, for the bulk viscosity, this has been demonstrated [38,39,45] to make the computation notoriously difficult. Moreover, there are also technical hurdles concerning the temperature control [46,47] during long MD runs near T c . One way of dealing with these problems is to carry out MD simulations of smaller systems and then to apply a finite-size scaling analysis, as done in Refs.…”