Kirkwood g-factor

Table 2 Dielectric Permittivity (e) and Kirkwood g Factor of Propylene Carbonate at Various Temperatures...

In a series of papers, H0ye and Stell have shown that the value of the dielectric constant and the associated Kirkwood G-factors can be related to the long-range behavior of the site-site correlation function The... 

Fig. 18. Values of g(k) for a Stockmayer fluid at p 0.8, r = 1.35, and —0.741. The curve is the QHNC theory, and the solid and open circles are the Ewald results of Pollock and Alder for A—256 and 500, respectively. The open square is the Ewald (A — 500) result for the Kirkwood g-factor.

The dielectric constant can be obtained from the rotational invariant coefficients of the pair correlation function. For example, following Fries et al., it can be evaluated using the Kirkwood g factor ... 

The major deviations from Onssger s equation are for hydrogen bonding liquids with water several aliphatic alcohols sulfuric formic and acetic acids HF and BCN and several amides as prime examples. The extent of the deviations is usually expressed by values of the Kirkwood g-factor defined on the basis of equation (21) by... 

The simulation values of correspond to a Kirkwood g factor equal to 2.7 again consistent %rith the general conclusion that centered point dipoles are not a good model for normal polar liquids. Brot et al have also examined the simulation consequences of assuming an off-center dipole at a distance r = 0.38 from the Lennard-Jones center and so approximately equivalent to a central dipole plus a central axial quadrupole. This results in a greatly reduced permittivity Cg > 11 1. With an approximate polarizability correction the permittivity of this model for CH p is about ten percent less than the experimental Cg = 22.5 at 206 K. 

An employment of effective dipoles determined from FIR bands has been proposed to enter the computation of static angular correlation factors, the Kirkwood g" factors. In the modified formula the integrated band intensity enters instead of the usual dipole moment value determined in vacuum (17). There, a dynamical property is being used to understand more closely the static structure, as controled by the angular position of neighbouring molecules with respect to each other. 

In the Onsager theory of isotropic dielectrics as well as in its extension to the nematic phase given by Maier and Meier the short range dipole-dipole correlations w e ignored. Therefore the dipole moment p in EQNS (1) - (3) cannot be identified with its value measured in the state [16]. The dipole-dipole correlations were considered in the theory developed by Frdtdich [17] who generalised the former Kirkwood approach [18]. Frdhlich has introduced the dipole-dipole correlation factor (known as the Frdhlich-Kirkwood g-factor) in the form... 

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