Abstract
We perform Monte Carlo simulations of a simple hard-soft dimeric model constituted by two tangent spheres experiencing different interactions. Specifically, two hard spheres belonging to different dimers interact via a bare hard-core repulsion, whereas two soft spheres experience a softly repulsive Hertzian interaction. The cross correlations are soft as well. By exploring a wide range of temperatures and densities we investigate the capability of this model to document the existence of structural inhomogeneities indicating the possible onset of aggregates, even if no attraction is set. The fluid phase behavior is studied by analyzing structural and thermodynamical properties of the observed structures, in particular by computing radial distribution functions, structure factors and cluster size distributions. The numerical results are supported by integral equation theories of molecular liquids which allow for a finer and faster spanning of the temperature-density diagram. Our results may serve as a framework for a more systematic investigation of self-assembled structures of functionalized hard-soft dimers able to aggregate in a variety of structures widely oberved in colloidal dispersion.
Highlights
The E-dependence on T is smooth and continuos and no kinks are observed, unlike documented, for instance, in a previous simulation study of cluster formation in patchy colloids [57]. This suggests that the mechanism of aggregation in hard-soft dimers is different from that observed in colloidal particles with anisotropic attractive interactions, since in that case the particles usually start to self-aggregate below a threshold temperature and this mechanism involves all particles in the simulation box
In this work we have investigated the onset of local inhomogeneities in a simple model of hard-soft dimers without any attractive interaction
In our approach two hard spheres belonging to different dimers experience a hard-core interaction, whereas two soft spheres interact via a soft
Summary
The formation of aggregates in systems composed by identical building blocks is a process of paramount interest in different fields of physical, chemistry, biology and material science [1,2].The spontaneous appearance of such structures under appropriate external conditions is observed in a large variety of systems, including colloidal suspensions [3,4], polymer nanocomposites [5,6,7], proteins [8,9], surfactants [10,11] and block copolymers [12,13,14]. One of the most successfull is based on patchy particles [15], which have been extensively studied by both experimental [16,17,18,19] and computer simulation [20,21,22] approaches According to such models, a single building block is usually considered as an hard sphere whose surface is decorated with a variable number of attractive sites (called patches) which lead the formation of aggregates through the self-assembly mechanism. A single building block is usually considered as an hard sphere whose surface is decorated with a variable number of attractive sites (called patches) which lead the formation of aggregates through the self-assembly mechanism This approach, well suited to study the formation of aggregates in surfactants and proteins, has been extended to dimeric systems, giving rise to patchy dimers [23,24]. Experiments [25] and computer simulation studies [26] have shown that patchy dimers can be succesfully used to encapsulate
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