Additive binary hard sphere mixtures: Eighth-order virial equation of state and stability analysis
Behara, Pavan Kumar
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An interesting question in statistical mechanics concerns whether mixtures of very different sized particles will demix, absent any energetic driving force. This question is usually posed in the context of two-component hard-sphere mixtures, for which parameters can be selected so these they resemble colloidal suspensions. The behavior can be modeled using either an effective depletion potential, which simplifies the complex system to a pseudo single component system, or explicitly, as a true mixture of two species. The demixing behavior for small size ratios (small-sphere to large-sphere diameter) is of particular interest as different methods to examine the model provide contradicting conclusions regarding even the qualitative features of the behavior. For highly size-asymmetric hard sphere mixtures, virial equation of state is obtained using novel chains and trees algorithm. MD data has been generated for many conditions. An Exponential approximant is used to improve the behavior of equation of state at higher packing fractions. Analysis has been done to see how the expansion converges and whether it is physically significant in explaining the fluid fluid separation.