Fig. 4.1-49 Ge. Temperature dependence of the high-frequency dielectric constant [1.48]. Experimental data points [ 1.49] and ah initio calculations (solid line)-, the dotted line is the theoretical result without the effect of thermal expansion, and the dashed line is the solid line shifted to match the experimental data |

Because of measurements of dielectric relaxation made at frequencies that were too low, and a long extrapolation to high frequencies, this parameter is frequently not determined precisely, and in the literature there are discrepancies between data reported for a given solvent. For instance, for DMF one may find the following values 2.51 [195], 3 [196], 4.5 [197] and 5.0 [198] op for DMF is 2.040. For other solvents also, the reported data of vary considerably. [Pg.257]

The CD function indicates that the dielectric loss (e") of glycerol follows the power law e" /Pcd at high frequencies (f fmx), where/max is the frequency corresponding to the dielectric loss peak. However, the high-frequency experimental data in Fig. 24 demonstrate a significant deviation from the expected asymptotic behavior both for CD and KWW functions, e" values [Pg.51]

Experimental methods are applicable for a wide range of frequencies. High-frequency measurements employ commercially available dielectric constant meters, Q-meters, and so on the impedance bridge method is widely employed at low frequencies. The levels of the frequencies applied experimentally are very important for data interpretation and comparison. [Pg.126]

As far as comparison with experimental data is concerned, the fractional Klein-Kramers model under discussion may be suitable for the explanation of dielectric relaxation of dilute solution of polar molecules (such as CHCI3, CH3CI, etc.) in nonpolar glassy solvents (such as decalin at low temperatures see, e.g., Ref. 93). Here, in contrast to the normal diffusion, the model can explain qualitatively the inertia-corrected anomalous (Cole-Cole-like) dielectric relaxation behavior of such solutions at low frequencies. However, one would expect that the model is not applicable at high frequencies (in the far-infrared region), where the librational character of the rotational motion must be taken [Pg.397]

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. [Pg.33]

Table 5.5 shows experimental values of E, E and the cohesive energies (from Table 5.3) for a number of AB compounds. The average energy gap results are those calculated from experimental data on high-frequency dielectric constants for the crystals. Later we will compare these values of E with those calculated from our earlier bonding models. [Pg.148]

Impedance data are presented in different formats to emphasize specific classes of behavior. The impedance format emphasizes the values at low frequency, which t5rpically are of greatest importance for electrochemical systems that are influenced by mass transfer and reaction kinetics. The admittance format, which emphasizes the capacitive behavior at high frequencies, is often employed for solid-state systems. The complex capacity format is used for dielectric systems in which the capacity is often the feature of greatest interest. [Pg.309]

We assume that if many of the liquids of interest, such as propylene carbonate, were studied by higher frequency (

© 2019 chempedia.info