Showing papers by "S. Chandrasekhar published in 1994"
TL;DR: In this paper, the authors examined the evidence for the occurrence of the biaxial nematic phase in low molecular weight thermotropic systems, and found that the isotropic phase transforms directly to the bi-lithmic phase in a first order transition.
Abstract: The evidence for the occurrence of the biaxial nematic phase in low molecular weight thermotropic systems is examined. The optical evidence for biaxility appears to be quite unambiguous for all the eleven cases discussed here. X-ray diffraction studies on magnetically aligned samples lend support to the optical evidence, but do not provide independent proof of long range biaxial orientational order. No X-ray studies on monodomain specimens have yet been reported. A noteworthy result, intriguing from the theoretical point of view, is that the isotropic phase transforms directly to the biaxial nematic phase in a first order transition for all the eleven compounds.
15 citations
TL;DR: In this paper, a simple mean-field-like (MF) behavior with negligible tricritical influence was observed in the vicinity of the A2−C2, Ad−Cd and A1−C1 transitions.
Abstract: The smectic A-smectic C (A-C) transition in several compounds has been shown to be mean-field-like (MF) with a substantial tricritical crossover effect. However, a simple MF behaviour, i.e., with negligible tricritical influence, had not been reported till recently. The heat capacity measurements of the MIT group in two compounds exhibiting the bilayer A2−C2 transition revealed such a behaviour. It is of interest to investigate whether a simple MF behaviour can be observed for partially bilayer Ad−Cd and monolayer A1−C1 transitions also. We report the first systematic order parameter measurements in the vicinity of the A2−C2, Ad−Cd and A1−C1 transitions. The data analysed in terms of power law and extended mean field expressions provide clear evidence of a simple MF behaviour in all three cases. The significance of this result is discussed.