Onsager cavity

FL, and the difference in dipole moments determined from the plot is 2.36 D if the Onsager radius is 0.33 nm [53]. The Onsager cavity radius was obtained from molecular models where the molar volumes were calculated by CAChe WS 5.0 computer program. The simplest method to estimate the cavity radius is to assume a = (3y/47r) 3, where V is the volume of the solute. 

This equation does not contain any information about sizes of the Onsager cavity and function of interaction and hence, this relation is quite general. If cos y is close to unity, the expression can be simplified ... 

On the basis of an Onsager cavity (23) model of dielectrics applied to a polar solute with an intrinsic dipole movement /xr° in its rth electronic state, Mazurenko gives an equation for the orientational free energy of the solute molecule in a pure polar solvent environment, which can be identified as equivalent to u/jlpe chem, thus 2... 

The physical significance of these variables is apparent when they are evaluated in the Onsager cavity description of solvation, which treats the solute as a sphere (which we will assume here is unpolarizable) of radius a. The solvent is modeled as a uniform dielectric medium with a static dielectric constant s and an optical dielectric constant op. The following relationships apply in the Onsager cavity description... 

A simple model for C(t). In this subsection we explore the relationship of C(r) to dynamic properties of the solvent, in terms of the Onsager cavity description, following the work in the literature on this subject [12-14, 53-57]. Theories that go beyond the Onsager model are described in Sections II.E and II.D. 

The Onsager cavity description of solvation treats the solvent as a dielectric continuum. The dielectric dynamics of the solvent is typically characterized by the frequency-dependent complex dielectric constant s(co). The measurement of (co) for a neat solvent is conventionally called a dielectric dispersion measurement. 

Several authors have discussed how C(r) can be calculated from the Onsager cavity model. Briefly, we need to consider the time-dependent reaction field, which was related above (Eqs. (12) and (15)) to C(t). For simplicity we consider the case of a probe with ps = 0 and 0. If the probe... 

The physical meaning of the relationship described in the previous subsection becomes apparent when we consider the popular special case of the Onsager cavity model that arises if we assume that the solvent s dielectric properties are well described by a Debye form. 

These results allow a test of the Onsager cavity model for a uniform dielectric continuum solvent with a dielectric response that is well modeled by Eq. (24). Our group recently tested this model for methanol. In this case, both high frequency (co) data (see Barthel et al. [Ill]) and short time resolution C(t) data [32] exist. 

The energy curves in Figure 22 are closely related to the Marcus-Hush theory for electron transfer. The formalism we employ emphasizes a dipole model for the solute solvent interaction, i.e., an Onsager cavity model. However, a Born charge model based on ion solvation as something in between [135] would be essentially equivalent because we do not attempt to calculate Bop and Bor but rather determine them empirically. 

The total local field FA is equal to the vector sum of the Onsager cavity field FA, and the Onsager reaction field.101 The latter is independent of EA, and results from the dipoles own fields.101 In the medium of dielectric constant n2, FA is ... 

The reality of the Onsager cavity is one of the reasons which prompted me to select this paper for this New Century Issue this is one of the further steps in the development of real models using the physical approach. This is not the only reason, however, Onsager introduced new concepts, that of the reaction field and that of the cavity field, with a clear and transparent physical basis, and devised a simple model based on a few parameters with physical meaning, and easily managed computationally. 

Therefore we consider that careful theories following the Onsager cavity approach are trustworthy as much as current experiments can decide. Besides, indications from recent simulation vork (25) lead to prefer the derivation by Mason and Fatuz-zo. Such a preference also meets the outcome of a critical examination from theoretical arguments (26). 

Figure 11. An elliptical unit is immersed in its own medium. The spherical cavity represented by the dashed line represents the Onsager cavity.

Kawski A, Kuklinski B, Bojarski P (2002) Z Naturforsch A 57A 716 Suppan P, Ghoneim N (1997) Solvatochromism. The Royal Society of Chemistry, London Koutek B (1978) Collect Czech Chem Common 43 2368. Onsager cavity radius ao = 4.41 A, from DPT Cam-B3LYP/6-31 + G(d)//IEF-PCM(UFF) calculations (present work) Ceron-Carrasco IP, Jacquemin D, Laurence C, Planchat A, Reichardt C, Sratdi K (2014) J Phys Chem B 118 4605... 

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