23 research outputs found
Fractionation of polydisperse systems: multi-phase coexistence
The width of the distribution of species in a polydisperse system is employed
in a small-variable expansion, to obtain a well-controlled and compact scheme
by which to calculate phase equilibria in multi-phase systems. General and
universal relations are derived, which determine the partitioning of the fluid
components among the phases. The analysis applies to mixtures of arbitrarily
many slightly-polydisperse components. An explicit solution is approximated for
hard spheres.Comment: 4 pages, 1 figur
Universal law of fractionation for slightly polydisperse systems
By perturbing about a general monodisperse system, we provide a complete description of two-phase equilibria in any system which is slightly polydisperse in some property (e.g., particle size, charge, etc.). We derive a universal law of fractionation which is corroborated by comprehensive experiments on a model colloid-polymer mixture. We furthermore predict that phase separation is an effective method of reducing polydispersity only for systems with a skewed distribution of the polydisperse property
Polydisperse star polymer solutions
We analyze the effect of polydispersity in the arm number on the effective
interactions, structural correlations and the phase behavior of star polymers
in a good solvent. The effective interaction potential between two star
polymers with different arm numbers is derived using scaling theory. The
resulting expression is tested against monomer-resolved molecular dynamics
simulations. We find that the theoretical pair potential is in agreement with
the simulation data in a much wider polydispersity range than other proposed
potentials. We then use this pair potential as an input in a many-body theory
to investigate polydispersity effects on the structural correlations and the
phase diagram of dense star polymer solutions. In particular we find that a
polydispersity of 10%, which is typical in experimental samples, does not
significantly alter previous findings for the phase diagram of monodisperse
solutions.Comment: 14 pages, 7 figure
Structure of Polydispersed Colloids with Attractive Forces:聽 HMSA Integral Equation and Monte Carlo Simulations
Phase transitions in simple fluids: an application of a one-phase entropic criterion to Lennard-Jones and point Yukawa fluids
A recently proposed entropic criterion [P.V. Giaquinta and G. Guinta, Physica A 187, 145 (1992)] for the determination of phase transitions in simple fluids is applied to two-fluid models, a purely repulsive point Yukawa fluid, and a 6-12 Lennard-Jones system. Both the gas-liquid and the freezing transitions are investigated by means of integral equation theory, and assessed with simulation data available in the literature. Our results indicate that the entropic criterion is a reasonable tool for predicting the freezing transition at low temperatures, in particular for purely repulsive potentials. Comparison with other melting rules is less favorable when there is an important attractive component in the interaction. On the other hand, the determination of the gas-liquid critical point and the liquid side of the gas-liquid coexistence curve is merely qualitative. Our results, however, show the existence of a correlation between the gas-liquid transition and the location of one of the inflection points of the density-dependent excess residual entropy