Structure and dynamics of the interface between a binary hard-sphere crystal of NaCl type and its coexisting binary fluid

Molecular dynamics simulations are performed to study the [100] and [111] orientations of the crystal-melt interface between an ordered two-component hard sphere with a NaCl structure and its coexisting binary hard-sphere fluid. The diameter ratio of the two types of hard spheres making up the mixture is taken to be 0.414. This work complements our earlier interface simulations [J. Chem. Phys.116, 3410] for the same diameter ratio at lower pressures where the smaller component is immiscible in the solid and the fluid mixture coexists with a pure FCC crystal of large particles. Density profiles and diffusion coefficient profiles are presented for the AB interfacial system. We find that for this system, the transition from crystal-like to fluid-like behavior of both the density and diffusion constant profiles occurs over a narrower region than that seen in our previous studies [J. Chem. Phys. 116, 3410] of the FCC/binary fluid system. But similar to what was found in the FCC/binary fluid interface the transition region for the large particle diffusion constant is shifted about the size of the large particles toward the fluid phase relative to that for the small particles.Comment: 8 page

Free energy calculations for solid solutions by computer simulations

Two techniques for calculating the free energy in a binary solid solution of hard spheres are presented. Both compute the free energy difference between a monodisperse system and the mixture. A reversible path is constructed from the solid solution to the monodisperse system—in one case by varying the composition and in the other by changing the diameter ratio. The relative merits of the two methods are discussed. We find that the technique in which the diameter ratio is changed appears more efficient. Examples of application of each technique are presented

Computer simulation of solid-liquid coexistence in binary hard-sphere mixtures

The authors report the first numerical simulation of the melting curve of a binary mixture. The melting curves of binary hard-sphere mixtures with diameter ratios alpha =0.95 and 0.90 were obtained by Monte Carlo simulation. For alpha =0.95 the phase diagram is found to be spindle-like; for alpha =0.90 it exhibits an azeotrope. They compare these findings with predictions based on density-functional theor

Simulation of the adhesive-hard-sphere model

Monte Carlo simulations of the three-dimensional sticky-hard-sphere system are presented. A new modified Monte Carlo algorithm has been developed which makes it possible to explore the phase diagram for a large region of both the packing fraction and the stickiness parameter t. The phase diagram is calculated, as well as pair distribution functions and structure factors. Cluster percolation has been studied and its relation to the phase diagram. The simulation results are compared with predictions, obtained from the Percus-Yevick approximation, which can be solved analytically for this model. The potential relevance of the present simulation results for experiments on clustering in neutral colloids is discussed

Thermodynamic properties of binary hard sphere mixtures

We present thermodynamic and structural data for binary hard sphere mixtures for diameter ratios α = 0·95, 0·90 and 0·85, obtained from computer simulations in the fluid phase in the face centred cubic solid phase. The equation-of-state data for the liquid are represented accurately by the semi-empirical equation of Mansoori. For the solid mixture the pressure is always found to be higher than that of the monodisperse system at the same packing fraction. We discuss techniques to sample the configuration space of binary mixtures efficiently. We have expressed all our simulation data for the solid phase in a compact way, by fitting them to a single symmetry-adapted analytical function

Computer simulation of solid-liquid coexistence in binary hard sphere mixtures

We present the results of a computer simulation study of the solid-liquid coexistence of a binary hard sphere mixture for diameter ratios in the range 0·85 ⩽ ğa ⩽ 1>·00. For the solid phase we only consider substitutionally disordered FCC and HCP crystals. For 0·9425 < α < 1·00 we find a solid-liquid coexistence curve of the ‘spindle’ type. For α = 0·9425 this becomes an azeotropic and for α = 0·875 a eutectic diagram. We compare these results with the predictions of the density functional theory of Barrat, Baus and Hansen. We observe that the density functional theory accurately predicts the point where the spindle diagram transforms into an azeotrope. However, the density functional theory differs from the simulation results on a number of counts. The greatest differences between computer simulations and theory are that the changeover from an azeotropic to a eutectic diagram is found to occur at α = 0·875, rather than at the predicted value of α = 0·92, that the density difference between the solid and the liquid at liquid-solid coexistence is found to have a minimum as a function of the mole fraction of the large spheres, while density functional theory predicts a maximum, and finally that the solubility of large spheres in a solid mixture of small spheres is much larger than predicted