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Weakly Attractive Systems

The value of the peaks and troughs in the pair distribution function represent the fluctuation in number density. The peaks represent regions where the concentrations are in excess of the average value while the troughs represent a deficit. As the volume fraction is increased, the peaks and troughs grow, reflecting the increase in order with concentration. We [Pg.160]

The first nearest neighbour shell as a function of concentration is an important quantity, indicating how the structure develops locally. If z is the number of nearest neighbours we can sum up all the particles in the first nearest neighbour shell to the minimum position in r2g(r) which marks the outer limit of that shell  [Pg.161]

In fact this basic idea allows us to intuitively connect the structure factor S q = 0) and the change in osmotic pressure. If we take q = 0 in Equation (5.28) we can see that it contains terms that are fluctuations in number concentration  [Pg.161]

The term D(r) is a pair potential that contains only the attractive potential, because the repulsion effects have been allowed for by the effective volume fraction and hard sphere diameter. The new potential can be defined as [Pg.164]

The first thing to note is the sigmoidal form of the curve as the concentration is increased the coordination number increases. As the [Pg.164]


Figure 6.13 A flow curve partially linearised using the Casson model for a weakly attractive system with the pair potential shown in Figure 5.9. The curvature at low stresses is indicative of a viscoelastic liquid. The Casson model successfully linearised the data where the particles can be visualised as aligning with the applied shear field. This would suggest almost complete breakdown of the aggregates... Figure 6.13 A flow curve partially linearised using the Casson model for a weakly attractive system with the pair potential shown in Figure 5.9. The curvature at low stresses is indicative of a viscoelastic liquid. The Casson model successfully linearised the data where the particles can be visualised as aligning with the applied shear field. This would suggest almost complete breakdown of the aggregates...
Close examination of the population ratios of the peri substituted compounds (Table 21) shows another point. That is, whereas the sc form of the methoxycarbonyl compound is less favored relative to that of the cyano compound when the peri substituent is methyl, the situation is reversed when the peri substituent is chlorine. Weak attractive interactions between a carbonyl moiety and a peri substituent bearing a lone pair of electrons are known in triptycene systems, and the methoxycarbonyl group is a stronger electron acceptor than cyano (148). This attractive interaction may be the cause for the seemingly anomalous populations. [Pg.59]

An analogy may be drawn between the phase behavior of weakly attractive monodisperse dispersions and that of conventional molecular systems provided coalescence and Ostwald ripening do not occur. The similarity arises from the common form of the pair potential, whose dominant feature in both cases is the presence of a shallow minimum. The equilibrium statistical mechanics of such systems have been extensively explored. As previously explained, the primary difficulty in predicting equilibrium phase behavior lies in the many-body interactions intrinsic to any condensed phase. Fortunately, the synthesis of several methods (integral equation approaches, perturbation theories, virial expansions, and computer simulations) now provides accurate predictions of thermodynamic properties and phase behavior of dense molecular fluids or colloidal fluids [1]. [Pg.118]

Figure 12. Penning electron energy distributions for systems with weak attraction between metastables and target. Figure 12. Penning electron energy distributions for systems with weak attraction between metastables and target.
The thermodynanucs of gas-phase species adsorbing on a surface can be separated into the classes of physical adsorption (physisorption) and chemical adsorption (chemisorption). The difference between the two classes of adsorption is related to the heat of adsorption, A Hads. In physisorption, weak attractive forces (van der Waals) such as dipole-dipole and induced dipole interactions drive the adsorption of species from the gas phase. For chemisorbed systems, chemical bonds associated with electron transfer between adsorbate and substrate are formed upon adsorption. Each of these interactions can be described by a two-dimensional potential-energy diagram as in Figures 10 and 11. [Pg.4739]

In concluding this Sect, on classical electronic spectroscopy, it should be mentioned that weak absorption bands of vdW systems are frequently partly overlapped or completely hidden by the strong bands of the subsystems. Nonetheless there are still quite a few attractive systems worth investigating by this method. [Pg.67]


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Colloidal systems weakly attractive

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