The Unreasonable Effectiveness of the Nallet Model

Abstract

In 1993, Nallet, Laversanne and Roux put forward a simplified model for the intensity scattered by lamellar phases, which was nonetheless very successfully used in fitting experimental results, especially those obtained with powder systems. I argue that the success as well as the simple expression of the model result from an approximate integration over sample orientation, resulting from an implicit integration over the scattering vector component normal to the director.