AbstractThe T – P phase diagrams of the halogenomethane compounds (CCl_4 – _ n Br_ n , n = 0, 1, 2, 4) are calculated using a mean field model. By expanding the free energy in terms of the order parameters for the transitions of the liquid (L), rhombohedral (R), face-centered cubic (FCC) and monoclinic (M) phases in those compounds, the phase line equations are derived and they are fitted to the experimental data from the literature. This method of calculating the T – P phase diagram is satisfactory to explain the T – P measurements for the halogenomethane compounds and it can also be applied to two-component systems.
A system of interacting relativistic bosons at finite temperatures and isospin densities is studied within the framework of the Skyrmelike meanfield model. The mean field contains both attractive and repulsive terms. The consideration is taken within the framework of the Canonical Ensemble and the isospindensity dependencies of thermodynamic quantities is obtained, in particular as the phase diagrams. It is shown that in such a system, in addition to the formation of a BoseEinstein condensate, a liquidgas phase transition is possible. We prove that the multiboson system develops the Bose condensate for particles of highdensity component only.
The phase behavior of the polydisperse An+1Bn multigraft copolymer melt is considered in a framework of weak segregation theory. The phase diagrams of melt are constructed within first harmonics approximation for two special cases: (i) lengths of backbone subchains between successive grafting points in each macromolecule are distributed according to the Schultz–Zimm distribution whereas lengths of side chains are fixed and (ii) both lengths of backbone subchains and side chains are distributed according to the same Schultz–Zimm distribution. The regions of stability of LAM, HEX and BCC mesophases in phase diagrams deform considerably as compared with the case of monodisperse graft copolymer. For both the cases the mean field phase diagrams indicate that order–disorder transition temperature grows as polydispersity index increases.
The information about liquid crystal phases that can be obtained by light scattering and by high-resolution X-ray scattering is reviewed. Results for the nematic-smectic A transition suggest the de Gennes-McMillan model is correct, but adequate theoretical solutions to the model remain elusive. Recent results on the smectic A to smectic C transition are presented that show unambiguously that it exhibits classic mean-field behaviour and this is explained by a Ginzburg criterion argument. Some preliminary results of a study of a nematic-smectic A transition in a lyotropic material are given and indicate similarity to thermotropic materials.
Characterization studies are performed on a ferroelectric liquid crystal, 12CN5(R*). Phase sequence and transition temperatures are obtained by polarized thermal microscopy. Temperature variation of spontaneous polarization and tilt angle in the smectic C* phase are found to agree with the mean-field predictions. Results obtained for the variation of the switching time and torsional viscosity with temperature are also presented.
Calculation of the T-P phase diagrams for the halogenomethane compounds (CCl-=SUB=-4-n-=/SUB=-Br-=SUB=-n-=/SUB=-, n=0, 1, 2, 4) using the mean field theory -=SUP=-*-=/SUP=-