Tricritical behavior of the smectic-A to smectic-C phase transition in a liquid crystal mixture

A phenomenological approach to the description of the smectic-A to smectic-C phase transition in a liquid crystal mixture is proposed. The problem of the first or second order transition is explored by means of the variation of the concentration. The influence of the concentration on this transition is discussed by varying the coupling between the concentration variable and the order parameters. We show that a tricritical point on the smectic-A to smectic-C phase transition line can be achieved under certain conditions. The theoretical prediction is found to be in good qualitative agreement with experimental results. (C) 2008 American Institute of Physics.