Denolf Katleen, Van Roie Bert, Glorieux Christ, Thoen Jan
Laboratorium voor Akoestiek en Thermische Fysica, Departement Natuurkunde en Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium.
Phys Rev Lett. 2006 Sep 8;97(10):107801. doi: 10.1103/PhysRevLett.97.107801.
By means of adiabatic scanning calorimetry, we have studied the effect of the nonmesogenic solutes cyclohexane (CH) and biphenyl (BP) on the nematic-smectic-A phase transition in the liquid crystal octylcyanobiphenyl (8CB). For all concentrations of BP studied, the transition remains second-order. For 8CB+CH, however, crossover from second-order to first-order is observed at a tricritical point of the mole fraction x of CH around 0.0460. The difference between the two systems and the crossover is explained in terms of a mean-field free energy density expression including coupling terms of x with the nematic and smectic-A order parameters.
