Phase Diagram of Kob-Andersen-Type Binary Lennard-Jones Mixtures

Abstract

The binary Kob-Andersen (KA) Lennard-Jones mixture is the standard model for computational studies of viscous liquids and the glass transition. For very long simulations, the viscous KA system crystallizes, however, by phase separating into a pure A particle phase forming a fcc crystal. We present the thermodynamic phase diagram for KA-type mixtures consisting of up to 50% small (B) particles showing, in particular, that the melting temperature of the standard KA system at liquid density 1.2 is 1.028(3) in A particle Lennard-Jones units. At large B particle concentrations, the system crystallizes into the CsCl crystal structure. The eutectic corresponding to the fcc and CsCl structures is cutoff in a narrow interval of B particle concentrations around 26% at which the bipyramidal orthorhombic PuBr_{3} structure is the thermodynamically stable phase. The melting temperature's variation with B particle concentration at two constant pressures, as well as at the constant density 1.2, is estimated from simulations at pressure 10.19 using isomorph theory. Our data demonstrate approximate identity between the melting temperature and the onset temperature below which viscous dynamics appears. Finally, the nature of the solid-liquid interface is briefly discussed.

Assessing the utility of structure in amorphous materials

“…As we approach the equimolar concentration, we see the two species A and B, increasingly sharing common local structures. Indeed, the equimolar AB liquid freezes into an AB crystal and does so far more rapidly than at the other two concentrations [27].…”

Experimental Evidence for a State-Point-Dependent Density-Scaling Exponent of Liquid Dynamics

“…that relaxation time is a function of entropy: τ (S ex ), by equating Eqs. 1 and 2, and recently the framework has been used to make predictions for properties of the melting line [17]. For the latter, the state point dependence of the scaling exponent is an essential ingredient.As a special case, Alba-Simionesco, Kivelson and Tarjus (AKT) have investigated the validity of a scaling law for activated dynamics where the scaling exponent only depends on density [18][19][20], but not on temperature.…”

Statistics of small length scale density fluctuations in supercooled viscous liquids

“…The upper half of particles have been made invisible to reveal the arrangement of particles in the 3 × 3 × 3 subvolume h. The structure correspond to a cubic CsCl crystallite. This is one of the known stable structures of the mixture 49.…”