ADIABATIC CALORIMETRY MEASUREMENTS IN THE VICINITY OF THE NEMATIC-SMECTIC A-SMECTIC-C MULTICRITICAL POINT

High-resolution adiabatic calorimetry has been used for the study of the nature of the NAC (nematic-smectic A-smetic C) multicritical point in the mixture of 4-n-hexyloxyphenyl-4 prime n-octyloxy-benzoate (608) and 4-n-hexyloxyphenyl-4 prime -n-decyloxybenzoate (6010). The N-C transitions are weak first order however the transition entropy disappears at the NAC point. The forms of the heat capacity anomalies in the vicinity of the NAC point are more complicated then those predicted by the simple mean-field theory. This result as well as the phase diagram topology manifest the fluctuation nature of the NAC point.