Heat-Capacity Study of the Transition from a Stacked-Hexatic-B Phase to a Smectic-A Phase

High-resolution ac calorimetry measurements have been performed on a liquid-crystal material exhibiting a stacked-hexatic-Bsmectic-A phase transition. The transition appears to be second order with a pronounced, symmetric heat capacity peak and no observable thermal hysteresis. The data can be fitted by a power law divergence with critical exponents ==0.640.04 and a ratio of critical amplitudes AA=0.83. Measurements have also been carried out on a crystalline-B-smectic-A transition which is found to be first order.