Observation of the Smectic C -- Smectic I Critical Point
  We report the first observation of the smectic C--smectic I (C--I) critical point by Xray diffraction studies on a binary system. This is in confirmity with the theoretical idea of Nelson and Halperin that coupling to the molecular tilt should induce hexatic order even in the C phase and as such both C and I (a tilted hexatic phase) should have the same symmetry. The results provide evidence in support of the recent theory of Defontaines and Prost proposing a new universality class for critical points in layered systems. 
S. Krishna Prasad, D.S. Shankar Rao, S.Chandrasekhar, M.E.Neubert and   J.W.Goodby