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Phase behavior of weakly polydisperse sticky hard spheres: Perturbation theory for the Percus-Yevick solution
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10.1063/1.2358136
/content/aip/journal/jcp/125/16/10.1063/1.2358136
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/16/10.1063/1.2358136

Figures

Image of FIG. 1.
FIG. 1.

Equation of state, from the energy route, for a one-component fluid of SHS. From left to right and top to bottom the four panels refer to a reduced temperature of , 0.50, 0.20, and 0.15, respectively. The continuous line corresponds to the MSA approximation, the dotted line to the mMSA approximation, the short dashed line to the C1 approximation, the long dashed line to the PY approximation, the dot-dashed line to the WCA first order perturbation theory, squares to the WCA second order perturbation theory (with error bars indicating the range where the true value should lie with probability of 99.7%), and triangles to the MC simulations of Miller and Frenkel (Ref. 20). In all cases the HS component of the pressure was chosen to be the one obtained from the compressibility route of the PY approximation (Ref. 39).

Image of FIG. 2.
FIG. 2.

The overlap volume of the two exclusion zones around colloid particles of diameter and which cannot be accessed by polymers of diameter .

Image of FIG. 3.
FIG. 3.

Phase diagram of the monodisperse SHS fluid obtained with the PY closure and the energy route to thermodynamics. Shown are the binodal and spinodal curves and the region where the PY equation has no solution [see Eq. (25)].

Image of FIG. 4.
FIG. 4.

Pressure from the energy route of the PY approximation for a single (parent) phase with case IV stickiness coefficients, plotted against volume fraction. Results are shown for several small values of the polydispersity (see legend) and well above, just above, and below (from left to right) the critical point of the monodisperse system. The pressure was determined using Eq. 9 of Ref. 22.

Image of FIG. 5.
FIG. 5.

Cloud and shadow curves for SHS mixtures with polydispersity , as obtained within the PY approximation and the energy route to thermodynamics, for coefficients chosen according to cases II and IV from Eq. (5). The shifts from the binodal of the monodisperse system (labeled “mono”) were calculated using Eq. (15) and give the leading corrections in a perturbative treatment of polydispersity. Note the collapse of the cloud and shadow curves, as expected from this order of the perturbation theory for purely size-polydisperse models (Refs. 32 and 33), and the divergence of the perturbation theory at the monodisperse critical point.

Image of FIG. 6.
FIG. 6.

Cloud and shadow curves for the SHS model with polydispersity and case V stickiness coefficients. The binodal of the monodisperse system is shown for comparison.

Image of FIG. 7.
FIG. 7.

Cloud and shadow curves for the SHS model with polydispersity and case I stickiness coefficients. The binodal of the monodisperse system is shown for comparison.

Image of FIG. 8.
FIG. 8.

Cloud and shadow curves for the AO model with polymer-to-colloid size ratio and (colloid) polydispersity . The binodal of the monodisperse system is shown for comparison.

Image of FIG. 9.
FIG. 9.

Fractionation in SHS mixtures with stickiness coefficients chosen according to cases II and I, at and for polydispersities as in the corresponding Figs. 5 and 7. Shown are the cloud (parent) size distribution , taken to be of the Schulz form, and the size distributions in the liquid shadow and gas shadow phases that form when coexistence is approached from low densities (gas cloud phase) and high densities (liquid cloud phase), respectively. For case II (main graph) the larger particles tend to accumulate in the liquid phase, while for case I (inset) the opposite is true.

Image of FIG. 10.
FIG. 10.

Decomposition of the difference in between gas and liquid phases. The two contributions and are plotted separately against ; the latter quantity is graphed on the vertical rather than the horizontal axis for ease of comparison with Figs. 5–8. Inset: ratio of .

Image of FIG. 11.
FIG. 11.

Cloud and shadow curves for case II stickiness coefficients and with polydispersity , calculated using the BCMSL-type free energy [Eq. (29)] rather than the PY approximation, as in Fig. 5. The binodal of the monodisperse system, which differs from the PY result, is shown for comparison. Main graph: region around the critical point. Inset: global view of the results on the same scale as in Fig. 5.

Image of FIG. 12.
FIG. 12.

Comparison of predictions for the AO model with polymer-to-colloid size ratio . Left: results of SHS mapping analyzed within the PY approximation; as in Fig. 8 cloud and shadow curves are shown for colloid polydispersity , along with the monodisperse binodal for comparison. The vertical axis now shows the polymer volume fraction rather than the reduced temperature . Right: analogous results obtained from free volume theory. Inset, right: fractionation coefficient for the two approximation schemes.

Tables

Generic image for table
Table I.

Coefficient of the perturbative expansion (6) of the adhesion parameters for the four cases listed in Eq. (5).

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/content/aip/journal/jcp/125/16/10.1063/1.2358136
2006-10-23
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Phase behavior of weakly polydisperse sticky hard spheres: Perturbation theory for the Percus-Yevick solution
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/16/10.1063/1.2358136
10.1063/1.2358136
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