Pinch point analysis and correlation length

Pinch points are visible in the structure factor map of the h = 145 nm sample, for example, at the point (2,2). To analyze this quantitatively, we extracted a line scan of the structure factor through the pinch point, from the point (3/2,5/2) to the point (5/2,3/2), plotted in Fig. 2E. As in (13), we calculated the correlation length in the system, ξ, from a Lorentzian fit to the intensity profilewhere q is the distance along the line scan, q₀ is the location of the pinch point, and A and B are constants. Fitting the data of Fig. 2E, we find A = 4.75, B = 0.25, and ξ = 10.8a ± 0.1.