Nature of a Nematic-Smectic-A-Smectic-C Multicritical Point

Recent x-ray data on the angles and 2-theta shifts in the smectic-C phase of a binary liquid-crystal mixture were analyzed via a mean-field theory. We demonstrated that the smectic-A-smectic-C transitions (AC) are mean-field-like. This conclusion is consistent with recent heat-capacity data along the AC transition line. Furthermore, the nematic-smectic-A-smectic-C point in this binary mixture is found to be in the vicinity of the tricritical point along the AC and nematic-smectic-C transition line.