Dielectric studies of trans-4-n-octyl-(4-cyanophenyl)cyclohexane (8PCH) at ambient and high pressure

Nematic Potential and Order Parameter Determined from Dielectric Measurements

“…It has been shown that such a theoretical calculation of S agrees fairly well with experimental results obtained by various methods at ambient pressure as well as at higher pressures [9,10]. In this work we apply such calculations for the analysis of recently obtained high-pressure dielectric data.…”

Crossover formulas in the kramers theory of thermally activated escape rates—application to spin systems

“…We remark, however, that due care must be taken in transposing the results of one calculation to another, as the physics is entirely different. It is necessary to recall that the Debye problem of relaxation including inertia, in a potential exemplified, for example, by a nematic liquid crystal of the type considered by Maier and Saupe (Coffey and Kalmykov and Urban et al [36,83]) is the exact rotational analogue of the Kramers translational problem of Section 11. Thus the noninertial limit of the rotational problem is governed by the (approximate) Smoluchowski equation and in the inertial case the three regimes of Kramers' particle problem will appear (IHD, VLD, and the frictional crossover region).…”

“…This will then yield a formula for the Kramers' escape rate for a rotator in a nonaxially symmetric nematic potential, say, if the inertia of the rotator is neglected. The principal practical use of such a formula would be to estimate [83] the retardation (g) factors [36] for dielectric relaxation of nematic liquid crystals in nonaxially symmetric potentials.…”

Relations between Nematic Potential and Order Parameters (P2) and (P4)

“…The order parameters can be derived from dielectric relaxation measurements that have already been employed by us to 8PCH [8]. The reliability of this procedure will be discussed in a subsequent paper [9] where order parameters derived for several nematics will be compared with those obtained by other experimental methods.…”

“…Another relation between S and a has been derived by Kalmykov and Coffey (KC) [ 10] in solving the Fokker-Planck equation for rotational Brownian motion with the use of the Maier-Saupe mean field potential. The exact solution of the problem can well be approximated by Also this equation was applied to results on 8PCH [8].…”