MOLECULAR-OPTICAL AND STRUCTURAL ANISOTROPY OF THE NEMATIC MIXTURE E7
The relation of the refractive indices nj of the nematic mixture E7 consisting of cyanobiphenyl derivatives for the light-wave polarization along (j = || ) and across (j = ^ ) the optical axis with the polarizability parameters (components gja, mean value gma = (g ||a+ 2g ^a)/3, anisotropy dga = g ||a- g ^a) and orientational order of a-type molecules comprising the mixture was investigated. The local-field tensor with components fj =1+Lj(nj2 - 1) was introduced for the mixture and the relationship between the Lorentz-tensor components Lj and the components Lja was established. The temperature dependences Lj(T) for the E7 mixture were obtained using experimental dependences nj(l, T). The relationship Lj(Lja) was confirmed. The temperature dependence of the material order parameter S(T) was obtained. The change of the mean value gm(Т) = (g ||  + 2g ^ )/3 for the studied mixture due to changing of S(Т) was observed. The dependence gm(S) was shown to be caused by two opposite-sign contributions due to changing conformation of molecular biphenyl cores and intermolecular interactions. The obtained results were compared with the consequences of using model tensors fj, which literature data are known for mixtures.