Landau theory of the nematic-smectic a tricritical phase transition in a binary mixture of liquid crystals

Abstract

To cite this article: H. Yurtseven (1995) Landau theory of the nematic-smectic a tricritical phase transition in a binary mixture of liquid crystals, Phase Transitions: A Multinational Journal, 53:1, 75-86,We have developed in this study athennodynamic model for the nematic-smectic A (NA) hicritical phase transition of a binary mixture of liquid crystals in analogy with the model for quasi fluid mixtures due to Griffiths. Using the Landau theory with a symmetrical TCP, we have predicted the critical behaviours of the nematic susceptibility, order parameter and the specific heat discontinuity in the vicinity of the TCP.Our predictions for the hicritical exponents for the order parameter and the specific heat discontinuity are those predicted by the mean field theory (&1/4 and a=1/2) with a symmetrical TCP. Our exponent value of y=1/2 for the nematic susceptibility does not agree with the mean field value of y=l.Our predicted values agree with those obtained experimentally for some binary mixtures of liquid crystals. This means that the mean field model with a symmetrical TCP is capable of describing the nematic-smectic A tricritical phase transition for a symmetrical binary mixture of liquid crystals.

λ‐transition of NH4Cl and ND4Cl at high pressures

“…(2)) is the same as in the Landau mean-field theory. As we mentioned above, the temperature and pressure dependence of those coefficients can be chosen in the order of α 2 ~ α 4 2 or b 2 ~ b 4 2 , which we have also considered in our thermodynamic model for the liquid crystals near the NAC point using the meanfield theory [56]. In Eq.…”

A phase diagram for ammonium halides

“…A first-order phase line can coincide with a secondorder phase line at the tricritical point (TCP) (Griffiths, 1970;. There exists a TCP in various systems, for example, He3-He4 mixture (Grafet al, 1967), mixtures of liquid crytals (Kobayashi, 1970;Mc Millan, 197 1;Yurtseven, ,1995Yurtseven and Salihoglu, 1992), Ni(N03)2.2H20 (Schmidt andFriedberg, 1970), DyAlG (Landau etal., 1971), SbSI (Peercy, 1975), KH2PO4 (Schmidt er al., 1976), BaTiO3 (Clarke and Benguigi, 1977).…”