Orientational correlation parameter

A different measure for the structuredness of solvents in terms of order, relevant to polar solvents only, is their dipole orientation correlation parameter (see Chapter 3) ... 

Figure 7 Single-molecule orientational correlation times (circles) from NMR data (57) and collective orientational correlation times (triangles) from OHD-RIKES data (56) as a function of rj/T and estimated static orientational correlation parameter (squares) as a function of temperature for acetonitrile-d3.

In addition to Trouton s rule, some other parameters for measuring the structuredness of solvents have been recommended, for example a solvent dipole orientation correlation parameter [175, 200], the solvent s heat capacity density [175, 200], and a so-called Ap parameter derived from the solvent s enthalpy of vapourization minus EPD/ EPA and van der Waals interactions [201], According to these parameters, solvents can be classified as highly structured e.g. water, formamide), weakly structured e.g. DMSO, DMF), and practically non-structured e.g. -hexane and other hydrocarbons) [200, 201]. 

In this section, we review some of the important formal results in the statistical mechanics of interaction site fluids. These results provide the basis for many of the approximate theories that will be described in Section III, and the calculation of correlation functions to describe the microscopic structure of fluids. We begin with a short review of the theory of the pair correlation function based upon cluster expansions. Although this material is featured in a number of other review articles, we have chosen to include a short account here so that the present article can be reasonably self-contained. Cluster expansion techniques have played an important part in the development of theories of interaction site fluids, and in order to fully grasp the significance of these developments, it is necessary to make contact with the results derived earlier for simple fluids. We will first describe the general cluster expansion theory for fluids, which is directly applicable to rigid nonspherical molecules by a simple addition of orientational coordinates. Next we will focus on the site-site correlation functions and describe the interaction site cluster expansion. After this, we review the calculation of thermodynamic properties from the correlation functions, and then we consider the calculation of the dielectric constant and the Kirkwood orientational correlation parameters. 

Another measure for order in a liquid is the Kirkwood dipole orientation correlation parameter (KDOCP) g, but this pertains only to dipolar liquids ... 

LOCAL FIELD FACTORS AND ORIENTATIONAL CORRELATION PARAMETERS 6.1 General Considerations... 

For the collective spectra (le dielectric and Rayleigh) < Mp> includes an orientational correlation parameter for example, in the Rayleigh case... 

To measure these orientational correlation parameters (or, more generally, to interpret spectral intensities in condensed phases) it is necessary to deal with the local field factor (1+G). The basis of a molecular theory of this factor has been formulated above as... 

To obtain the orientational correlation parameters gx and g2 from the reorientational parts of the permittivity or the depolarised... 

Kg. 8.5 The intermolecular orientational correlation parameter of two bond segments, s,j(d), in the first layer of 0.2 nm thiekness adjacent to the walls and in a similar layer far from the walls. (Redrawn from Ref. 21.)... 

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