A semianalytical “reverse” approach to link structure and microscopic interactions in two-Yukawa competing fluids

Abstract

We study theoretically a prototype hard-sphere two-Yukawa model with competing interactions, under thermodynamic conditions associated with the formation of clusters. We adopt the analytically solvable random phase approximation and show that this theory predicts reasonably well the structure of the fluid-in comparison with exact Monte Carlo results-within a unique parameterization of the direct correlation function inside the hard core of particles. In particular, the theory follows correctly the development, in the structure factor, of a local peak at low wavevectors, as peculiarly associated with the onset of aggregation. We then model the direct correlation function in the same wavevector regime by a Gaussian function, so as to systematically investigate, in a "reverse" scheme, how varying the properties of the local peak modifies the original underlying competing interaction. We show that large variations in the height of the peak are generally associated with comparatively smaller variations in the height of the microscopic repulsive barrier; moreover, the shrinking and shifting towards lower wavevectors of the peak may be interpreted in terms of the displacement of the barrier, producing a substantial enlargement of the range of both the attractive and repulsive contributions to the interaction potential. Finally, we document the way the repulsive barrier tends to vanish as the two-Yukawa fluid approaches a "simple fluid" behavior, heralding the onset of a liquid-vapor phase separation. Published by AIP Publishing. https://doi.

Isomorph invariance and thermodynamics of repulsive dense bi-Yukawa one-component plasmas

“…Excluding the Coulomb limit µ = 0, the mean relative deviation between Eqs. (19,21,23,25) and the IEMHNC approximation result is 0.1% whereas the maximum relative deviation is 3.3% for the 4000 (σ, µ = 0, Γ, κ) combinations studied. Higher deviations are generally observed for large values of κ and low values of Γ/Γ m , see also Ref.…”

“…Combining all the above, the reduced excess internal energy for dense repulsive biYOCP liquids is described by Eqs. (19,21,23,25). Excluding the Coulomb limit µ = 0, the mean relative deviation between Eqs.…”

“…We shall refer to such strongly-interacting systems as bi-Yukawa one-component plasmas (biYOCP). It should be emphasized that the biYOCP interaction potential differs from the prototype two-Yukawa or double-Yukawa potential used to describe pair interactions in colloid-polymer mixtures, which also involves a hard-core repulsion [17][18][19].…”

Structure of self-assembly amphiphilic systems: Relation between phenomenological parameters and microscopic potential parameters

“…For mathematical convenience, c 2K lr (q) has been calculated analytically with the direct correlation function, c 2K lr (r) −β u 2K (r), extended inside the core 52 . Even if the structure factors determined by RPA are not so accurate than those of simulation or integral equations calculations, it has been proven that RPA is an efficient tool to predict the particularities of the structure factor for systems with competing repulsion and attraction interactions 73 .…”

Soft core fluid with competing interactions at a hard wall

“…For systems with competing interactions in the bulk, a large body of research has been reported. The studies have been done in the framework of computer simulations [24,26,27], including those in combination with machine learning techniques [28], approaches such as Landau-Brazowski theory [29], integral equations [24,25,30], and density functional theory [25,[31][32][33]. Far fewer results exist for systems under confinement.…”