Temperature study of cluster formation in two-Yukawa fluids

Abstract

An accurate thermodynamically self-consistent integral equation theory of the liquid state is used to investigate model fluids with competing attractive interaction at short distances and long-range repulsion, focusing on thermodynamic states where the formation of clusters is expected to occur. We find a remarkable accuracy of theoretical predictions, through a detailed assessment against results of Monte Carlo simulations. The behavior of theoretical radial distribution functions and structure factors faithfully follows the onset and growth of cluster aggregates in the homogeneous dense-vapor phase. The thermodynamic properties of the system sensitively depend on the ratio between the repulsive barrier and the attraction strength. We elucidate the role of accurate theoretical tools to investigate the properties of fluids with complex phase behaviors.

Communication: Thermodynamic signatures of cluster formation in fluids with competing interactions

“…2,4,5,8,10,14 In this Communication we provide strong and consistent evidence for jump discontinuities of structural and thermodynamic properties under well-defined thermodynamic conditions, which yield clear-cut signatures of the onset of clustering.…”

“…This feature is well reproduced by theoretical calculations, based, e.g., on fluid integral equations, and by Monte Carlo (MC) simulations using the model pair potential (1). 3,5,8,15 For appropriate choices of z 1 , z 2 , and R, the amplitude of the prepeak increases with K 1 , while its position shifts towards lower wavenumbers. 2,8 In fact, the random phase approximation 2 and a mean field version of density functional theory 6,7 0021-9606/2012/137(1)/011101/4/$30.00…”

“…13 Upon increasing R or z 1 , particles tend to aggregate into finite clusters, eventually leading to microphase separation which preempts the macroscopic GL transition. [2][3][4][5][6][7][8] The cluster size is determined by a subtle balance between the SA, which favours the onset of aggregation, and the LR, which limits the growth of clusters. A widely used diagnostic of aggregation is provided by the static structure factor S(q) (q = kσ is the reduced wavenumber).…”

“…All simulations have been carried out on a sample composed of N = 4096 particles, enclosed in a cubic box with periodic boundary conditions (corresponding to an interaction cutoff Exploiting the experience gained from earlier calculations for the model potential (1), 8 we have focused on a restricted portion of the large parameter space (z 1 , K 1 , z 2 , K 2 ). In order to study the influence of the attractive length scale 1/z 1 on the clustering, K 1 is increased (or equivalently the temperature is decreased) for a given z 1 value while fixing z 2 = 0.5 and R = 0.1 at the packing fraction ϕ = πρσ 3 /6 = 0.2.…”

Structure and phase behavior of colloidal dumbbells with tunable attractive interactions

“…[70,71]), as well as in theoretical and numerical investigations of model fluid with microscopic competing interactions (see e.g. [72,73] and references). Recently, such a feature in the structure factor has been more generally related to the presence of some kind of "intermediate-range order" in the fluid [74,75].…”