Correlation functions in mixtures with energetically favoured nearest-neighbours of different kind: a size-asymmetric case

Abstract

Binary mixtures of hard-spheres with different diameters and square-well attraction between different particles are studied by theory and Monte Carlo simulations. In our mesoscopic theory, local fluctuations of the volume fraction of the two components are taken into account. Semi-quantitative agreement between the simulation and theoretical results is obtained, except from very small distances. The correlation functions exhibit exponentially damped oscillations, with the period determined by the interaction potential, and both the amplitude and the correlation length increasing significantly with increasing diameter ratio. Increasing size asymmetry leads also to decreasing fluctuations of the number of the smaller particles in the attractive shell of the bigger ones. For small size asymmetry, the strongest correlations occur for comparable volume fraction of the two components. When the size ratio increases, the maximum of the structure factor moves to a larger volume fraction of the bigger particles, and for the size ratio as large as 4, the maximum goes beyond the accessible range of volume fractions. Our results show that when the neighbourhood of different particles is energetically favoured, the particles are much more uniformly distributed than in the random distribution even at relatively high temperature, especially for large size asymmetry.

28 pages, 20 figures

References in corpus (9)

• The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration
• Density functional theory for hard-sphere mixtures: the White-Bear version Mark II
• Field theory for size- and charge asymmetric primitive model of electrolytes. Mean-field stability analysis and pretransitional effects
• Two-dimensional pattern formation in ionic liquids confined between graphene walls
• Field-theoretic description of ionic crystallization in the restricted primitive model
• Self-assembly in a model colloidal mixture of dimers and spherical particles
• Monte Carlo cluster algorithm for fluid phase transitions in highly size-asymmetrical binary mixtures
• Correlation functions in ionic liquid at coexistence with ionic crystal. Results of the Brazovskii-type field theory
• Complex Self-Assembly from Simple Interaction Rules in Model Colloidal Mixtures