Chan, Kelby K.Deutsch, MosheOcko, B. M.Pershan, PeterSorensen, L. B.2013-03-011985Chan, Kelby K., Moshe Deutsch, B. M. Ocko, Peter S. Pershan, and L. B. Sorensen. 1985. Integrated x-ray-scattering intensity measurement of the order parameter at the nematic-to-smectic-A phase transition. Physical Review Letters 54(9): 920-923.0031-90071079-7114http://nrs.harvard.edu/urn-3:HUL.InstRepos:10357694The temperature dependence of the square of the smectic order parameter, \(\mid \psi \mid^2\), was determined from the integrated x-ray scattering intensity. The data are described very well by the form \(I(t)/I(0)=1 \mp A^{(\pm)}\mid t \mid^x\), where \(t=(T-T_{NA})/T_{NA}\). The determined values for x do not agree with the theoretically expected value \(x=1-\alpha\), where \(\alpha\) is the heat-capacity exponent. This disagreement raises questions concerning the quantitative validity of the Landau–de Gennes free energy.en-USJournal Article2013-03-0110.1103/PhysRevLett.54.920