CALORIMETRIC AND STRUCTURAL CHARACTERIZATION OF THIN LIQUID-CRYSTAL FILMS EXHIBITING THE SMECTIC-A-HEXATIC-B-CRYSTAL-B TRANSITIONS

High-resolution heat-capacity and electron-diffraction measurements have been conducted on thin free-standing films of a liquid-crystal compound exhibiting the smectic- A-hexatic- B-crystal- B transitions. Despite the absence of herringbone order, the liquid-hexatic transition in extremely thin films has nevertheless been found to show a pronounced pretransitional heat-capacity anomaly, in disagreement with the predictions of two-dimensional melting theory. © 1995 The American Physical Society.