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Quasi-chemical approach

When there is a large difference between ys(A) and ys(B) in the equation above, there must be signihcant deparmres from dre assumption of random mixing of the solvent atoms around tire solute. In this case tire quasi-chemical approach may be used as a next level of approximation. This assumes that the co-ordination shell of the solute atoms is hlled following a weighting factor for each of tire solute species, such that... [Pg.354]

Putting these together in accord with the quasi-chemical approach gives ... [Pg.62]

A more accurate type of quasi-chemical solution model was introduced by Guggenheim [E. A. Guggenheim, Mixtures (Oxford University Press, New York, 1952)] to account for specific A + B AB association corrections in both Hfs (x) and st(x). The quasi-chemical approach employs an explicit pair partition function for the equilibrium population of A B complexes in solution. More general associated solution models were also developed to incorporate AB complexes of other than 1 1 stoichiometry [A. D. Pelton and M. Blander. Metall. Trans. 17B, 805-15 (1986)]. Although such quasichemical and solution models can be more accurate, they are also more difficult to implement. [Pg.272]

The equilibrium concentrations of point defects can be derived on the basis of statistical mechanics and the results are identical to those obtained by a less fundamental quasi-chemical approach in which the defects are treated as reacting chemical species obeying the law of mass action. The latter, and simpler, approach is the one widely followed. [Pg.22]

When approximations are made in the evaluation of those distinct terms, the sum needn t be independent of definition of the iimer shell. We argue here that when the sum is insensitive to local adjustment of the inner shell then the inevitable approximations are well balanced. The quasi-chemical approach is variational in this sense. [Pg.153]

There seems to be a well-developed folklore that judicious explicit inclusion of a small number of solvent (water) molecules can dramatically improve the accuracy of imphcit hydration models (Gilson et al, 1997). An important physical observation is that an appropriate inclusion of an inner shell only can capture most of the effects of the solvent on the solute of interest (Beglov and Roux, 1994 1995 Bizzarri and Cannistraro, 2002). The quasi-chemical approach is the theory for inclusions of that sort. [Pg.170]

With this example we also address the issue that quasi-chemical approaches sometimes offer flexibility in designing an inner shell, and differently designed approaches permit us to learn different features from the molecular statistical thermodynamic calculations. [Pg.208]

Panayiotou, C., Vera, J. H. (1980). The quasi-chemical approach for non-randomness in liquid mixtures. Expressions for local composition with an application to polymer solution. Fluid Phase... [Pg.33]

Vera and Panayiotou used the quasi-chemical approach and suggested the following expressions for the... [Pg.147]

C. Panayiotou and J. H. Vera. 1980. The quasi-chemical approach for nonrandomness in liquid mixtures Expression for local surfaces and local compositions with an applications to polymer solutions. Fluid Phase Equilib. 5 55. [Pg.734]

A lattice-gas approach to ion-ion and ion-solvent interactions (treated via a quasi-chemical approach or Monte Carlo simulations). [Pg.167]

A.D. Pelton and M. Blander, Thermodynamic analysis of ordered liquid solutions by a modified quasi-chemical approach-application to silicate slags. Metallurgical Transactions B, 17B (1986) 805-815. [Pg.60]

Heidemann et al also presented a discontinuous method to calculate spinodal curves and critical points using two different versions of the Sanchez-Lacombe equation of state and PC-SAFT. Moreover, Krenz and Heidemann applied the modified Sanchez-Lacombe equation of state to calculate the phase behaviour of polydisperse polymer blends in hydrocarbons. In this analysis the polymer samples were represented by 100 pseudo-components. Taimoori and Panayiotou developed a lattice-fluid model incorporating the classical quasi-chemical approach and applied the model in the framework of continuous thermodynamics to polydisperse polymer solutions and mixtures. The polydispersity of the polymers was expressed by the Wesslau distribution. [Pg.306]

Correlation and Prediction via the Quasi-chemical Approach.—Equations (29) and (35), whose derivations involved differing definitions and assumptions, express p and V in terms of the equilibrium constants for the formation of groups of r molecules from single molecules at a particular temperature r, but for p, V, T correlation over a temperature range these equations are of limited utility, since the jfiC s are likely to be temperature dependent. In relation to equation (35), the variation of the with temperature can be expressed by the thermodynamic relation... [Pg.199]

It may be concluded that the quasi-chemical approach offers a means of correlating p, K, T for gases which show marked departures from ideality. Thus Prausnitz et have calculated B T) for both steam and... [Pg.201]

In 3 we used the quasi chemical approach for the order-disorder problem. We have chosen this particular method because of the intuitive character of the quasi-chemical equation which shows in a clear way how the "ordering" parameter ze affects the local order as expressed by the number of couples Nab- However the quasi-chemical treatment being based on a guess of the form on the combinatorial factor g NA, Nb, Nab) it is necessary to test it by comparison with exact treatments. [Pg.64]

On the basis of such an adsorption step, we are led to the following question Would a quasi-chemical approach with structure elements, sometimes limited to surface zones, lead to significant progress by opening not only descriptive but also prevision prospects ... [Pg.183]

Ale] Alex, K., Mclellan, R.B., A Quasi-Chemical Approach to the Thermodynamics of Ternary SoUd Solutions Containing Both Substitutional and Interstitial Solute Atoms , J. Phys. Chem. Solids, 32(2), 449-451 (1971) (Thermodyn., Calculation, 24)... [Pg.618]


See other pages where Quasi-chemical approach is mentioned: [Pg.87]    [Pg.88]    [Pg.89]    [Pg.142]    [Pg.171]    [Pg.202]    [Pg.65]    [Pg.68]    [Pg.429]    [Pg.87]    [Pg.314]    [Pg.54]    [Pg.171]    [Pg.55]    [Pg.508]    [Pg.599]   
See also in sourсe #XX -- [ Pg.405 ]




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