RESUMO
Gordon Barrett (GB): Research Associate, Centre for the History of Science, Technology and Medicine, University of Manchester, UK (special issue co-editor).
RESUMO
We present a theoretical study of the dynamic displacement-displacement and intensity-intensity (for coherent soft x-ray scattering) correlations in Sm-A as well as Cr-B free-standing films. The work is based on a continuous hydrodynamic model that allows one to calculate efficiently the dynamic correlation functions and considerably simplifies earlier analyses of finite-size and surface effects in Sm-A films. The model is extended to Cr-B films. We show that despite the crystalline order, the Cr-B film is a strongly fluctuating system, which is due to an abnormally small shear elastic constant. An easy-shear approximation is developed to describe the fluctuations in the Cr-B phase. We predict nonmonotonic behavior of the intensity-intensity correlation function in both Sm-A and Cr-B films. The analysis can be applied to either coherent x-ray or conventional laser dynamic light scattering experiments.
RESUMO
The smectic-A phase boundaries of a hard-spherocylinder fluid are calculated using a density-functional theory based on one proposed earlier by Somoza and Tarazona [Phys. Rev. A 41, 965 (1990)]. Our calculations do not employ the translation-rotation decoupling approximation used in previous density-functional theories. The calculated phase boundaries agree well with computer simulation results up to aspect ratios L/D approximately 5 and are in better agreement with the simulations than are previous theories. We generalize the model fluid by including long-range interactions with quadrupolar orientational symmetry, which are taken into account by mean-field approximation. For sufficiently large strength, these interactions produce a smectic-C phase, which undergoes either a continuous or weakly first-order transition to the smectic-A phase. The theory and numerical methods discussed here can be applied to the analysis of interfacial phenomena.
