Generalized mean-field model for the smectic-A–chiral-smectic-Cphase transition

Abstract

In light of our high-resolution and almost simultaneous measurements of the tilt angle and polarization in the chiral-smectic-C phase of p-(n-decyloxybenzylidene)-p-amino-(2-methylbutyl)- cinnamate (DOBAMBC), we have proposed a generalized mean-field model to describe the important features related to the smectic-A–chiral-smectic-C transition. This mean-field model is similar to the one proposed by Zeks. After carrying out least-squares fittings to the generalized mean-field model, we demonstrated that the temperature dependences of the tilt angle, polarization, and their ratio are well described by the model. The fitting to the temperature variation of the helical pitch is less satisfactory but the qualitative feature of the helical pitch anomaly is obtained. Furthermore, all the mean-field expansion coefficients can be calculated. Among the eleven coefficients, seven are in good agreement with the existing reported results, the four remaining will be reported here for the first time. The shortcoming of the prevailing phenomenological mean-field theory by Pikin and Indenbom will be discussed in detail.