Published in Physical Review Letters, Volume 98, Issue 19, May 8, 2007, pages 197801.1-197801.4.
Copyright © 2007 American Physical Society. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Physical Society. The following article appeared in Physical Review Letters and may be found at http://dx.doi.org/10.1103/PhysRevLett.98.197801.
We show that Landau theory for the isotropic (I), nematic (N), smectic-A, and smectic-C phases generically, but not ubiquitously, implies "de Vries" behavior: i.e., a continuous A-C transition can occur with little layer contraction while the birefringence increases significantly once the system moves into the C phase. Our theory shows that 1st order A-C transitions are also possible. These transitions can be de Vries-like, but in general need not be. Generally, de Vries behavior occurs in models with unusually small orientational order and is preceded by a first order I-A transition. These results correspond well with experimental work to date.