Orientational and positional order in a tilted hexatic liquid-crystal phase

We present a synchrotron-x-ray study of the smectic-C (SC) and smectic-I (SI) phase in a single-domain freely suspended film. Weak bond-orientational order in the SC phase evolves continuously into the SI phase so that the two phases are not thermodynamically distinct. From a Fourier analysis we obtain the hexatic order parameter C6, the coefficient of cos6. The higher &, with fnfn+0.3n(n-1), in agreement with a scaling theory. © 1986 The American Physical Society.