Underlying framework of structural decay in binary hard-sphere mixtures

In liquid mixtures, changes in structural decay have been observed in particle simulations and experiments, and are an important element of their analysis. The work presents a comprehensive description of the long-range behavior of structural pair correlation functions of binary hard-sphere (BHS) mixtures. It is revealed that in BHS mixtures there exists a well-defined framework throughout the entire phase diagram of the particle sizes and fluid densities. The framework is based on special points representing the asymptotic oscillatory decay of the correlation functions as a superposition of three different wavelengths, whose arrangement shows surprising regularity and is described by power functions. The disclosed framework sets a limit on the particle size ratio for the presence of these special points and related structural crossover effects in the phase diagram. Similar frameworks are expected to occur in different binary mixtures. They can help resolve structural correlation functions at intermediate particle separations in different regions of the phase diagrams of asymmetric mixtures.